- A STUDY OF. THE DECAY
RESISTANCE OF COPPER-META-
ARSENITE TREATED WHITE FIR
LUMBER
[ABIES CONCOLOR LINDLEY
AND GORDON]

Thesis for the Degree of M. S.
MICHIGAN STATE COLLEGE

Frederick H. VogeI
I939

’1-

54'" '

‘ b

.5)

2'1"

”‘3‘

 

 

 

 

 

 

A STUDY OF THE DECAY RESISTANCE OF
COPPERrMETA-ARSENITE TREATED WHITE FIR.DUMBER

(ABIES CONCOLOR LINDLEY AND comes)

by
FREDERICK HAROLD voem.

if-! m h‘

\

Submitted in partial fulfilment of the requirements
for the degree of Master of Science in the
Graduate School of Michigan State College

Department of Forestry

June 1939

.N. .I $1,141.“ ‘

Altlri

 

 

«masts

v.‘ ii. v I

II .

To John Vogel

(137LL - 1938)

121495

 

 

i . «hill—I... .dr‘ .1! .u

THESIS APPROVED:

 

Acting Head of Department of Forestry, In Charge of major.

Head of“Botany Department, In Charge of Minor, and
Dean of the Graduate School.

ACKNOWLEDGMENT

It is with a feeling of deep and growing respect for the talents
of his guiding professors that the candidate submits this thesis. His
attempts in the realm of pure research and especially his analysis of
the results bring most forcibly to mind the fact that his guiding pro-
fessors have long ago surmounted equally difficult problems and have

progressed to attainments far beyond a project of this scope.

Guidance in the technical laboratory work is gratefully acknowl-
edged to Professor Forrest 0. Strong, whose grasp of the subject and
whose ability to demonstrate it clearly have lightened the work. To
Dean Ernst A. Bessey it is wished to acknowledge credit for an absorbing
course in Mycology, the very foundation for understanding the organisms
used in the work. To Professor Stanley E. Crowe there is owed a debt
of gratitude for extra personal help and advice in courses on the mech-
anics of statistical analysis. To Professor William J. Baker there is
acknowledged a manifold debt: for his constant inspiration from the in-
ception of the project to its fruition: for his aid in surmounting the
curricular problems which have arisen from time to time; and for his

counsel in matters pertaining to industrial applications.

Were the entire graduate project to have produced no more than the
friendship of these men, it would have more than repaid the candidate's

investment of time and effort.

 

 

TABLE OF CONTENTS

HISTORICAL BACIGROIND - - ’ - - - - -
DISCUSSION OF CREOSOTE VERSUS METAL SALT PPESERVATIVES
COPPER-INTA-ARSENITE - - - - - - -

THE AGENCIES DESTRUCTIVE TO WOOD - - - - -
GENERAL BACKGROIRID — - -
SOME NOTES ON THE STRUCTURE OF WOOD - - -
THE AECHANICS OF DECAY - — — - -
WOOD DECAY FUNGI

MARINE BORERS - - - — .. .. ..
TERJEITES - - — - - - _
POWDER POST BETLES ' - - — .. .. _
CARPENTER ANTS - - - - .. .. _
FIRE - — - - - .. - ..

LABORATORY METHODS OF PRE ERVATIVE TESTING

GENERAL PROCEDURE OF EXPERIEERT

SELECTION OF WOOD - - — .. .. _.
SELECTION OF GLASSWARE - -— - _ ..
SELECTION OF CULTURES - - - - .. ..
MERIHENTAL PROCEDURE - — ‘. .. - ..
RESULTS - - - - — - - _ _ ..
TABLES - — - — — — - _ -
PHOTOGRAPHS - - - - -

PLATE I. RESULTS OF TESTS OTT STERILIZA'I‘IOT‘.I

PLATE II EDITRE’YE VARIATIONS IN CHEMOTROPIC
RESISTANCE

PLATE III EJ‘ITRAIE DAMAGE TO TREATED WOOD

DISCUSSION - - - - - - - .. .. -
CONCLUSIONS - - - — - - - s - .. -

LITERATURE CI in - - - - - - .. - -

69-30
Sl-su
81

82
8h

85
90

 

 

...-... pult.‘ u!" ....M“
I

i

INTRODUCTION

Until recent years the lumber industry was like an orphan child
who grew to maturity without guidance or care. The industry did not
realize the economic basis on which it was builded; it did not realize
its potentialities; it failed to realize (almost disastrously) that it
must fight competition with knowledge, improvement and trade promotion.

While competitive industries -- iron, steel, brick, concrete and
fiber building board -- grew tremendously on the strength of the more
dependable physical data they could and did make available, our lumber
industry stood complacently by and watched the path to its door grow
less and less traveled. When the.industry's leaders did awaken,
they were faced with a dual problem: that of holding their remaining
markets, and that of fighting to regain lost markets vital to the exist—
ence of certain branches of the production industry.

Markets lost because steel and concrete could be relied upon to
conform to certain physical specifications (while timbers varied widely
within the same grade, and were seldom sold with engineering data to
guide their use) are being fought for with the aid of conferences on
uniform grading, with modern physical testing apparatus, and with
research laboratories. Markets lost because of slipshod manufacture
and careless handling are being regained through the adoption of uni-
form standards and attention to eye appeal such as labeling and pack-
aging. Markets lost because of lethargic salesmanship are being
contested with nation-wide sales promotion campaigns, advertising,
contests, legislative lobbying and vast credit facilities. And that

which concerns this paper most, markets lost because wood lacked the

necessary durability, are being regained through the deveIOpment and
application of dependable wood preservatives.

For wood preservatives the last hundred years has been a period
of juvenile trial and error; only in the very last two decades has the
scientific approach been evident. Many preservatives on the market
today would be discarded, at least for certain specific applications,
if there were complete studies made on them. Some preservatives or
systems of application would be revived after their discard through
the same means.

Most widely known and used of all wood preservatives, and with
good reason, is coal-tar creosote, with service records extending back
as long as ninety years (19). But creosote, with all its proven ser-
vice records, has certain inherent qualities which render its use
impractical in some applications. As a result, a great body of com-
petitive preservatives has sprung up to fill the gap left by those
unsatisfied demands, and incidently, to compete with creosote where
possibly the coal-tar product would serve as well or better.

Copper-meta-arsenite is a relatively new wood preservative. The
chemical nature of it is discussed in the body of the paper. There are
many additional questions to be answered in regard to COpper-meta-arsen-
ite, but this paper concerns itself with but one -- the decay resistance
to nine different fungi of white fir wood treated with it.

In order to present a coherent paper, it has been deemed advisable
to survey, cursorily, most of the field of wood preservation, and to
present the story in logical order from the beginning of history to the

culmination of this experiment.

 

(19) See citation 19 in list at end of this paper.

A STUDY OF THE DECAY RESISTAHCE OF
COPPER-META—ARSENITE TREATED WHITE FIR LUMBER
(ARIES CONCOLOR LINDLEY'AED GORDON)

HISTORICAL mercam

 

The practical application of wood preservation is not new; it is
not even comparatively new. Its experimental beginnings are shrouded
in remote historical antiquity: in the heyday of Egyptian embalming; in
the wooden sculpture and architecture of Greece. There is ample evi-
dence on hand today to show that wood was intentionally preserved
thousands of years ago, notably that of museum specimens of wooden
articles found in Egyptian tombs and about Grecian excavations.

Several investigators, among them 8.3. Boulton (l9).believe that
the five great orders of classical architecture were derived from
wooden ancestors. On the stone columns of these orders may be seen
vestigal remains of the block of stone upon which the wooden pillar used
to sit to ward off decay; of the slab or tile that used to cap the wooden
pole or pillar to throw off the rain; and even of the metal h00ps which
were placed around the pillars to prevent them from splitting, evoluting
now to decorative moldings.

Early scientific data arelacking - as we define the term "scien-
tific" today - but there are Egyptian papyrus fragments in many museums
which record some phases of the preservation of organic material, as
the bodies of kings, with "natrums" (68) (120a) (122a), spices, oils
and ”bitumens" (67) (68). We cannot chemically reproduce these sub-
stances, since the ancients left no exact formulas, but we believe that

the preserving solutions and oils must have been the concentrated waters

 

(19). Numbers in parentheses refer to citations at end of thesis.

 

 

it? I.”

\_0

of certain salt-bearing lakes still existing user Cairo (in which are
found mixtures of sodium—sesnui-carbonate, sodium chloride and sodium
sulphate)2: the natural oils or asphaltums found in seegage pools or
lakes, such as we know in Iraq and Trinidad today; and many natural
aromatic oils and spices.

It is interesting to review what little is known of Egyptian em—
balming. Herodotus (57) and Diodorus Siculus (Ml) wrote that bodies were
steeped in natrum for seventy days and then imbued with oils.

Rouyer, who was in Napoleon's Egyptian foray of 1798, believed
that the bodies were oven baked to take up oils after the long natrum
treatment (38) (lEEb), although no ancient author records that opinion.
It seems more probable, however, that the bodies were dried naturally
by the low humidities prevalent in the country back from the Nile,
otherwise the kiln drying of the bodies must have been recorded as
significant.

According to Howard Weiss (The Preservation of Structural Timbers.
N.Y.: McGraw-Hill. 1916), the Egyptian wooden coffins were not preserved
artificially. Their durability was to be accounted for only by their very
low moisture content. Weiss states that sycamore was largely used in the
construction of these coffins, and he pictures an almost perfect Egyptian
specimen in the MetrOpolitan fluseum of Art, New York. On the other hand,

Balfour states that the wood used in mummy cases came from the species

 

Cordia sebestena L. Dr. Ernst A. Bessey points out the fact that Cordia
sebestena L. is a native of the American tronics and could not have been

used in Egyptian mummy cases.

 

2.
The American Society of Civil Engineers in its timber preservation

Report of 1885 says: "Chemical analysis of the mummies of Egypt shows
arsenic in large nuantities in every portion -- and even in linen
vestments . . . (3. page 235)-

 

 

il‘1113,

 

Pettigrew (122) worked on mummies in his analyses of embalming
materials. He found such a thorough penetration of preservatives that
even the bones were saturated (page 62). He also found (page 60), sig-
nificantly, that the stony heart from an Egyptian mummy began to putrify
when the preservatives were withdrawn by maceration after 3000 years!

One of the earliest Greek objects of value to be preserved was
Phidias' wooden statue of Zeus (19). It was said to be located in a
damp forest at Olympus, and had its wooden base protected from decay by
saturation with certain preserving oils. The statue of Diana at Ephesus
was entirely of wood, which Pliny records (l?3b) (according to Husicianus,
an eye-witness) was kept from decaying by the application of oil of
Hard-bush in numerous small bore holes.

Pliny recommended rubbing wood with oil of cedar to protect it
against decay and worms. According to his writings (193c &123d), forty-
eight different kinds of oils were extracted from various trees, plants
and fruits to preserve wood, and Pliny details the various processes of
extraction(123d). There was probably no recourse to other preservatives
except the aforementioned Egyptian natrum and bitumens. Herodotus (67)
records many oils, resins, tars and pitches which were extracted and pre-
pared from trees, plants and mineral deposits. Various Greek and Roman
authors have written that the astringent portions of olive oil (amurca)
(27) (123a), and oils from cedar, larch, juniper and Hard-bush (Valeriana)
(123a) were used as preservatives. Probably many of the oils employed
were of doubtful value.

According to 3.3. Boulton, who made an exhaustive study of the
subject, there was no mention of salts of metals for wood preservation

by the ancients (l9).

 

 

w.—

11

It is interesting to learn that considerable was known, practiced
and written about the art of wood preservation years before the Christian
era. But we find no mention of further progress, nor hardly a mention
of the wood decay problem at all, until after the time of the world scien-
tific reawakening, less than three hundred years ago.3

And although the ancients knew and practiced the art of wood pres—
ervation thousands of years ago, they left no record which might indicate
that they had a theory of what wood decay actually was. Apparently they
considered it in the light of a natural phenomenon, like night which
naturally follows the day, but which can be alleviated with the aid of
oil or candle lamps.

Actual theories are not apparent until the 18th century, toward
the end of which scientists generally indicated that they believed decays
and putmfactions were due to fermentations of some kind. Zallinger (178),
according to Whetzel (177), believed that fungi found associated with
plant diseases were only abnormal growths of the plants themselves, re-
sulting from the disease rather than being a cause of it. His ideas
influenced pathological thought for a long time. Liebig and Pasteur
fought out the theory of ferments until Pasteur finally convinced the
world that Liebig's theory of "eremacausis" was wrong -- but he failed
to convince Liebig (106).

In the period in which the "phlogiston" theory was in vogue, many
eminent scientists subscribed to the belief that decay was due to the
escape of an unknown substance called phlogiston. Scheele and Priest-

ley subscribed wholeheartedly to it. Dr. Priestley, who first discover-

 

3' Aristotle (3814-322 3.0.) and Theophrastus (371-286 13.0.) wrote on
tree diseases. Plinius Secundus (23-79 A.D.) has already been cited.
Colerus, in 1600: Laurenberg, in 1631; and Hesze, in 1690, wrote fur-
ther on the subject.

Caesalpinus (1583) was the first to gather together the known fungi
in his "De Plantis."

12

ed oxygen, called it "dephlogisticated air." Dr. McBride (Qua) wrote
later that decay was caused by the liberation of carbon dioxide.

Leading up to our modern concepts of the phenomenon, we find Theo-
dore Hartig in Germany in 1833 seeking the cause of wood decay. His
analysis was faulty, as we see it today, probably because of the weight
of the current line of thought - spontaneous generation.

In 1839 we find that Weigmann published a nuaint statement of
similar vein in regard to fungi associated with certain tree diseases:
”The pus of the blight as well as that of the canker contains putric and
humic acid . . ."(1us). In 18MO Unger (160) came forward with the theory
that fungi, conidiophores and spores were transformed morbid sap of

diseased tissue. From 1837 to l85h Corda brought out his Icones fungorem

 

which did much to show the light on fungi. In 18H1 Meyen, in his

Pflanzenpathologie, refuted Weigmann with the statement, "smut mass is not

 

to be compared with animal pus." In 1851 Bonorden's Handbuch der Mykologie

 

 

gave to the potato famine in Ireland credit for the development of fungus
study.

In 1866 Anton de Bary brought out his Morphologie und Physiologie

 

der Pilze, Flechten und gyxomyceten, a contribution that was to lay the

 

foundation for real scientific mycology. Hubert Martin (116) says that
the definite recognition of parasitism of fungi dates from 1853 when

de Bary published his work die Brandpilze. In 1866 M. Willcomm pub-

 

lished a comprehensive analysis of the causes of decay, verifying
Theodore Hartig's belief in spontaneous generation(73). It remained
for Hartig's son, Robert, to fathom the secret and to bring to light

the true relation h between decaying wood and the fungi which are

‘A

E,
By "true" relation, the writer abides by the broad conception of the

term. Pathologists today still debate upon the exact physiological
behavior of wood-attacking fungi.

13

always present. In 1878 Robert Hartig's first publication on the sub-
ject caused a storm of controversy, but he had known the truth for many
years before he made it public.

Paul Sorauer (lh8) led a strong school of thought that held to a
"predisposition theory": Sorauer believed that wood had a natural ten-
dency to succumb to wood rot fungi when external conditions were of the
requisite kind.

In 1768 there was recorded the first British patent on a wood pre-
servative, and in 1770 Sir John Pringle published a list of antiseptics,
being copied later by Dr. McBride(hhb).

Toward the close of the 18th century and early in the 19th, the
pressing needs of the British Admiralty Department for ship timbers be-
gan to stir the first research on wood preservation. Good ship timbers
were growing steadily scarcer and delays in repairing rotted ships were
becoming alarmingly frequent. Many English writers record all too plainly
the price that England was paying for her lack of knowledge on timber
protection. The records of the Admiralty Department are choked with
dusty correspondence relating to rotted beams and knees and decking,
and delays in replacing them.

Samuel Pepys(121), author of the famous diary, who was a Secretary
to the Admiralty in the reigns of Charles II and James 11, left a record
that lays the problem as bare as the bedrock disclosed by a mountain
avalanche. Pepys(121), Ramsbottom(127) and Albion(l) have covered the
subject in dramatic style.

In 1812 Lukin tried an experiment of injecting ship timbers with
resinous vapors at the Woolwich Dockyard (h5b), but the results proved

the method a failure. Nevertheless, it was a step in the right di-

rection because highly resinous woods had been observed to be, and are
still known to be, generally resistant to decay. Even the ancients
recorded that woods with highly resinous odors lasted the longest(l23e).

Sir Humphrey'Davy (HSa) suggested the use of corrosive sublimate,
and Thomas Wade, in 1815. suggested salts of copper, iron and zinc -
thereby making himself one of the earliest proponents of the compounds
represented by the preservative studied in this thesis.

When the iron and steelclad ship came into its own and spelled the
end of the romantic old wooden ships-of—the-line (and the end of the
Admiralty's worry over the depleted ship building resources) it did
not spell the end of research on wood preservation: far from it, the
seeds of research had been sown and the first meager harvests arrived in
time for the birth and rise of the railroad industry, an outlet, ulti-
mately, for more wood and more species of wood than ever was dreamed of
by the British Admiralty'Department. Oliver Evans' Philadelphia steam
wagon of 1782, and James Watt's Birmingham engine of 178M have laid
the foundations for a vast network of railroads over the world. The
growth of railroads in this country may be traced from a humble begin-
ning on the Baltimore and Ohio in the 1830's to a climax in 1890, when
new track laying began to slack off noticeably. Slow expansion occurred
until 1916, when over 25M,OOO miles of railroad line were actually being
operated. (119).

Few students of the history of wood preservation fail to note the
tremendous influence of our railroads on the rise and growth of the pre-
servative industry. Thus Hartley (59) lays the great impetus of
preservation to the railroads. as does Schmitz (1M0). Evidence is
not lacking in the long lists of patent specifications. that a large

percentage of them were aimed specifically at railroad ties, as for

15

instance citation (105). Schmitz (130) says that wood preservation in
the United States began seriously in 1838 when the North Central Rail-
road of Maryland, now a part of the Pennsylvania system, erected a plant
to Kyanize chestnut ties with mercuric bichloride solution. Ten years
later the first commercial plant was erected at Lowell. Massachusetts,
to treat wood with mercuric and zinc salts for the locks and canals on
the Merrimac River.

In the 1850's preservation plants were erected by the Vermont
Central, the Chicago, Rock Island and Pacific, the Boston and Albany,
and the Erie Railroads to treat ties with zinc chloride.

In the 1860's the Philadelphia and Reading, the Old Colony, and
the Chicago, Burlington and Quincy Railroads began treating ties. The
Old Colony Railroad plant, erected in 1865 at Somerset, Massachusetts,
was the first in the United States to use creosote.

The first wood preservation plant in Michigan was erected in 1867
by Seeley of New York at the St. Clair Flats government project. It
was across Lake St. Clair from Detroit. at the mouth of the St. Clair
River.

The first copper-sulphate treated ties were laid about 1870 in
the United States by several railroads, but without marked success.
Thilmany treated with this process for the Wabash, the Pennsylvania
and Ohio, the Lake Shore and Michigan Southern, the Cleveland and Pitts-
burgh, and the Baltimore and Ohio Railroads.

Modern timber preservation probably began in the United States in d
1875 with the installation of a creosote plant at West Pescagoula,
Mississippi. This plant was erected for the Louisville and Nashville
Railroad, and it met with success from the beginning. From that time

until the present, the preservation industry has grown steadily.

16

Wooden railroad ties, universally next to the ground except on
trestles and on the pavement in cities, were subjected to the severest
conditions favorable to decay. Research begun for improving wooden
ship construction fell naturally into that for prolonging the life of
railroad ties.

Hundreds of chemicals and compounds were recommended by as many
investigatorss, and a flood of patent applications began to inundate the
British Patent Office, to be followed by similar floods of patent appli-
cations in France, Italy. Germany and the United States. An idea of
the trend of the times may be gained by a superficial study of less than
a decade of patent abstracts in one technical paper, the Journal of the
Society of Chemical Industries.

In 1882 we find three disclosures worthy of mention: Cross (35)
describes a process utilizing powdered asbestos in silicate of soda as
a preserving and fireproofing treatment; Card(26) patented a process
using chloride of zinc followed by a hot creosote bath to prevent leach-
ing: and Glazer(55) describes a coating formed by the use of zinc vitriol
followed by chloride of calcium.

Three years later we find Gardner (53) patenting a complicated
material called "Ceralin” in which are mixed linseed oil. colophony,
doubly rectified American petroleum, levigated litharge, zinc sulphate,
potash alum and carbolic acid. The whole was to be boiled two hours and
let stand for two days, whereupon it became an excellent preservative

paint. Lake(103) describes an improved Thilmany process6, in which the

 

5' Chapman (29) wrote in 1817 that almost everything under the sun had
'been tried as a wood preservative in the past five years.

6' Hr. I. Thilmany in 1870 worked on putting copper sulphate into tree
trunks, and later perfected the process by first injecting muriate of
'barytes followed with capper sulphate by Boucherie process. Finally
Thilmany adopted the pressure treating tank.

17

modern system of running trucks into the treating cylinder on rails is
used, complete with provision for keeping the loads from floating. He
recommends the use of barium chloride followed by cupric chloride.
Another Lake (10%) patented a system in which steaming and drying was
employed before treatment with antiseptic vapor. The same man (105)
was allowed the first patent for treatment of whole trunks of felled
trees, using a hollow cap and pump to get the preservatives into the
timber. Adaptations of this system are still in use (86).

In 1886 Mancion (11H) patented a process utilizing arsenic acid,
carbolic acid and ferrous sulphate. In the same year we find in
Germany some work by Filsinger (MS) on the value of aluminum chloride
for preserving oak and fir. Filsinger decided that while the crude
aluminum salt was all right, it was much improved by the addition of
salts of iron. Free hydrochloric acid was proved to be detrimental to
wood, and the whole aluminum chloride system was judged to be rather
expensive.

In 1887 four patents show the trend that was develOping: Hoyle
(138) describes a system of treating green wood by boiling off the ex-
cess water in heated oil similarly to the modern Boulton system, and
then treating the wood under air or liouid pressure. Stevenson(l52)
patented a preservative for wood block pavement, consisting of wood tar,
oil of resin and colophony. It was claimed to be proof against frost
injury and to resist slipping when wet. Quarante and D'Escalonne (196)
describe another complicated mixture of acetate of alumina or soda,
subacetate of lead. pyrolignite of lead, glycerine and water. This
mixture was either overenthusiastically described or the industry is
overlooking the answer to its prayers, for it was deemed‘imputrescible,

uninflammable and nearly incombustiblefi The inventors claimed, as a

18

side blow at competitors, that creosote destroyed the fiber of wood

and that sulphate of copper decayed wood in contact with iron or gal-
vanized iron. Under severe conditions, there was claimed to be no sign
of decay in ten years. McLea and Punshon(112) obtained a patent, for
both preserving timber and rendering it non-inflammable, in which
calcium chloride and ammonium phosphate were the chemicals named.

One patent. added in 1888 to the growing list of new compounds
and improved processes, included Avenarius'(7) patent for chlorine
treatment of tar oils to make "carbolineum", a preservative with no bad
odor, said to be better all around by the inventor. Modifications of
this compound are still to be found on the market today. A German
writer, Rittmeyer(137), published in this same year a historical de-
scription of various methods and results of wood preservative treatment.
Rittmeyer described, among others, sulphate of copper, sulphate of iron,
sulphate of zinc and sulphate of barium; chloride of mercury and chlor-
ide of zinc; creosote and tar oils: and mixtures of these. He also
included a table of costs that should be interesting to investigators
who are exploring this field. (Compare with (111) and (156))

In 1889 McMahon(113) took out a patent on a mixture of mercuric
chloride, ammonium chloride, soft soap, methylated spirit, water and
Venice turpentine. The race to patent every possible preservative or
combination of preservatives was especially marked during the middle
and last thirds of the 19th century, and these few examples serve only
to show the variety of patentable ideas.

By 1838 there were already four great basic patents extant, upon
which foundation the vast preservative industry has largely been builded
(85) (19): J.J. Lloyd Margary's sulphate of copper(115): Sir William

Burnett's chloride of zinc(2u); and John Bethellfls heavy oil of tar(16),

19

which did not even mention the name "creosote".

These patents were not the result of sudden brilliant inspirations
by the inventors, but were rather the crystallizing of a century's
random thought and experiment. Thus Boulton writes(19) that bichloride
of mercury, a very poisonous compound, was successfully employed as
early as 1705 by Homberg, a French savant; it was also recommended by
De Boissieu in 1767, although the Dutch Government was unsuccessful in
official trials with it in 1730, according to the same author, and
others (85). The Encyc10paedia Brittanica of 182M says that Sir
Humphrey'Davy recommended it for timber, as mentioned before. Kyan’s
patent in 1832 (101) is thus seen to be the culmination of more than a
hundred years of other men's work. While still used in certain appli-
cations, mercuric salts are looked on with disfavor for open use, as on
railroad ties where cattle have poisoned themselves by licking the salt
(3. page 286).

And similarly for sulphate of copper, since DeBoissieu and Bor-
denave first recommended it (120C) (85) in 1767, just seventy years prior
to its patent by'Margary7 in 1837 (115). Thomas wade (MSa) officially
recommended its use in 1815. It was tested by Evans on the Southern
Railway of Chile in 1857 (3). Cepper salts are still popular in
France today, not only as wood preservatives but as general fungicides.
It is well known that many genera and even orders of lower fungi are
killed outright or at least severely inhibited in growth by low con-
centrations of copper salts, and many of the higher fungi react
similarly. Dr. Boucherie8 patented a trunk injection method in 1838

under French Patent No. 11061.

 

7‘ It should be noted in passing that Margary's original patent covered
a mixture of sulphate and acetate of cOpper.

8' Dr. Boucherie was a celebrated French chemist who made many experiments
on the timber preservation problem between 1836 and 18h6.

Chloride of zinc was recommended first by Thomas Wade in 1815
(h5a) and by Dr. Boucherie in 1837 (120d). It was patented in the
United States by Sir William Burnett as a steeping process in 1838
'(ZH), and it remains pOpular to this day for many uses where the treat—
ed wood is not subject to direct leaching.‘ Of all the common preser-
vative chemicals, it is the most economical to use from the standpoint
of first cost.

Heavy oils, tars and creosotes follow the lead of the Egyptians
who employed “bitumens” in their embalming. According to Boulton (19),
Knowles described the use of tar oils as early as 1756. Franz M011
patented in Germany a heavy oils process in 1836 (117) in which patent'
was the first use of the word "Kreosot." John Bethell's American patent
of July, 1838 (16), although covering the field fully with the mention
of eighteen different antiseptics, makes no mention of creosote by that
name.

Boulton (19) refers to a report of the East Indian Railway
Company for 1867, which records the pronounced success of creosoted
sleepers after sixteen years experience with them. Mr. Boulton also
cites papers by McMaster in 1859 and 1863 on the subject of Permanent
flay materials in India, and by Danvers in his annual report to the
Secretary of State for India for 1863.

The history of wood preservation is still being made, and it is
being recorded in numerous technical Journals as this thesis is written;
it is impossible to write ”finis" to a study of it. The various pub-
lications of the American Wood Preservers' Association (h) (5) (6), the

magazine Phytopathology, the Journal of Forestry, the Review of Applied

21

Mycology and others carry a never-ending history of the development
of wood preserving.

For students interested in the history of wood-preserving patents,
one of the finest sources of information lies in three volumes of the
Proceedings of the American Food Preservers' Association; 1915, 1916
and 1935.

Great names have become engraved on the roster of researchers in
the field of preservation and pathology, names such as the Hartigs,_
Boulton, Bethell, Kyan, Chanute, Burnett, lillkonm, Falck, Holler, Kuhn,
Munch, Mayr, Tubeuf, Neger: Ward, Biffen, Bayliss, Hiley, Buller, Faull,
White; Berkeley, Smith; Von Schrenk, Spaulding, Atkinson, Rankin, Long,
Ihetzel, Weir, Bessey, Meinecke, Hunt, Humphrey, Hubert, Boyce, Richards
and Schmitz. Not a name here but what carries meaning to an enthus-
iastic student of the field in which many hundreds of names might have

been cited.

DISCUSSION OF CREOSOWE wWIRSUS METAL — SALT PRESERVATIVES

It has been brourht out clearly in the historical introduction that
coal-tar creosote has long been a major factor in wood preservation, at
least since the art and science of preservation began its enlightened
growth about a hundred years ago. There is a reason for it just as there
is a reason for the popularity of water as a solvent. Creosote serves
the purpose cheaply and dependably, for all its homely nature.

But just as we turn to other solvents for special solutes, we turn
to special wood preservatives to fit certain specific applications where
other factors outweigh the cheapness, the availability, and the ease of
handling of creosote. We can hardly pass on to a consideration of cop-
per—meta-arsenite without a brief dissertation on creosote and how it
fits into the economic scheme.

The firSt recorded mention of tars and related compounds is cred-
ited by Knowles with having occurred in 1756 in England and America (19).
First mention of the use of distillation products of gas-tar for preserv-
atives was by Franz M011 (117) whose German patent in 1836 first made
mention of the word "KREOSOT."

Bethell is reSponsible for the practical introduction of the creo-
sote process, according to Boulton, even though Bethell's basic patent of
1836 (16) did not mention creosote by that name; it included instead a
list of eighteen oils, tars and metallic salts, alone and in mixture.

The pertinent mixture which most concerned this paper was one of coal-tar
thinned with dead oil of coal-tar.

Of course, technically correct nomenclature would confine the term

creosote to a product of the destructive distillation of wood, but

23

modern usage gives the name to the coal-tar product, not chemically
identical. Wood creosote is seldom used as a wood preservative,
although it has merit, chiefly because it is not available in sufficient
quantity with uniform characteristics. It is also likely to run highly
acid and to attack metals.

183M Runge, a German chemist, discovered carbolic acid, an active in-
gredient of coal-tar creosote. EXperience seemed to bear out theories
which laid most of the value of coal-tar to that acid (which is not cor-
rosive to iron or steel). Later it was demonstrated that while carbolic
acid was a valuable constituent, it could not have been alone responsible
for the long preservation records; it was too volatile. The heavier toxic
oil constituents must have been responsible for the longest service
records.

The active preserving ingredients of coal-tar creosote are known
to be multiple, consisting of carbolic and cresylic acids, naphthalenes,
and many other related toxic compounds and alkaloids (13) (19).

It may be worthwhile to brief the process of coal-tar manufacture:
coal is heated in the absence of air or presence of steam for the pro-
duction of gas. Four products are derived from the process: commercial
or illuminating gas, ammoniacal liquor, coal tar and coke. The anti-
septic products ere all obtained from the distillation of the coal-tar,

a black gummy substance; thousands of very valuable chemicals, dyes
and flavorings have also been recovered from the same material.

Light fractions distil off the coal tar first, running strongly
to crude naphthas, of negligible value in preservation; next come the
heavy oils in which the preserving factors are concentrated: and finally

come the pitches and residue.

Disregarding a long technical discussion of creosote, we will con-
fine our remarks instead to the physical properties and attributes which
place creosote where it is - at the head of the field - and to the phys-
ical drawbacks which have lead to the introduction of numerous competi-
tive preservatives such as copper-meta—arsenite.

First and foremost, creosote is cheap to produce in tremendous
quantities with comparatively uniform characteristics. True, every coal
region produces a distinct type of creosote oil, but since commercial
coal fields are extensive. great ouantities of coal-tar over decades
or even centuries of time are normally available from each district.

And were one lot of creosote to be substituted for another from a differ-
ent region, the difference in preservative value would be of small sig-
nificance. Not so with wood-tar creosote, which varies greatly between
producers in the same area, and which is not normally available from a
given manufacturer in large enough quantities to satisfy the demands of
even one large treating plant. Wood-tar creosote is also comparatively
expensive.

Secondly, and with almost equal weight with cheapness and avail-
ability, is creosote's toxicity per unit of weight. Creosote is an
excellent fungicide, not only cheap in bulk cost, but cheap per-unit-
toxicity cost.

Creosote is fairly easily handled and it penetrates wood acceptably
well, both rapidly and deeply. It is permanent in its effect and resists
washing and leaching almost, but not quite, ideally. (The phenols and
cresols will leach out to some extent in water, but other insoluble toxic

agents remain in the wood.)

It does not corrode metals, and to all practical purposes does not
decompose wood fiber, Quarente and D'Escalonne (126) to the contrary.
It is not deliquescent.

But (and here lies the answer to the growing popularity of salts
of metals) creosote has certain inherent faults, not cheaply remedial,
which preclude its use for many specific applications:

Creosote has a strong, objectionable odor: a black, ugly color: it
leaves a dirty, oily surface to handle; it is irritating to many people‘s
skine;it often tends to bleed out of heavily treated timber on hot days:
it can be painted over only with considerable difficulty and added ex—
pense; it adds to the heat of burning timbers and throws off a thick,
black smoke; and lastly, some of the toxic ingredients are volatile, as
the phenols, cresols and naphthalenes.

Various salts of metals overcome all these difficulties without
trouble, but they fail on one or two very important points wherein
creosote gains its enviable record - cheapness and freedom from measurable
leaching. A few salts of metals fail on only one point; they may leach
badly, but most compounds which come so close to the ideal are high in
cost, are deliquescent, add color to the wood, are corrosive to metal or
are extremely poisonous. I

Bateman and Baechler (ll, entire series) and Waterman, et al,

(176) have analyzed many wood preservatives, with the following
recommendations:

All mineral acids and acid reacting salts such as the soluble
salts of aluminum, iron and tin are toxic to fungi but they attack
wood, too, and slowly decrease its strength. The same criticism holds
true for strong alkalies and strongly alkaline salts such as sodium

carbonate and trisodium phosphate.

26

Some salts attack iron and steel. These salts include some of
those of mercury, copper, nickel, cobalt and antimony.

Many toxic compounds are unstable, including catechol and
pyrogallol.

Some preservatives fail because they are too volatile. These
include benzene, toluene, xylene, phenol, ortho-, meta-, and para-
cresol, chlorobenzene, nitrobenzene, benzaldehyde and iodine.

Many compounds are too expensive: thymol, pyridine, mercuric
chloride, benzyl aniline, mercurochrome, alpha naphthol, benzoic
acid, picric acid, soluble molybdates and soluble salts of cadmium,
cobalt, uranium, thallium, thorium, silver and gold.

Preservatives must be toxic below 28°C. to come within the
range of fungus growth, and they must be toxic to all the wood
destroying fungi rather than to a selective few.

Hundreds of proprietary compounds have been placed on the market
to compete with creosote, but none has so far succeeded as well on its
own merits as has creosote. The writer may be questioned on this point,
but let the questioner look into the capitalization behind the most
successful proprietary salt preservatives on the market: names like Bell
Telephone, Westeranhion, General Electric, American Telephone and Tel—
egraph, Weyerhaeuser, Mellon and the like are identified with funds
for active trade promotion, lobbying and advertising. Many preservatives
on the market are sustained only by the pressure of the money behind
them -- and not by their merits. Wood preservation is big business
today: copper—meta-arsenite is only one of a crowd.

It is easily seen why competition with creosote is logical, and

why the place of any competitor in the field depends upon two supports:

27‘

l. the physical characteristics in which it happens to be superior to
creosote, and 2. the confidence of the public.

Unfortunately up to the present, the claims of certain promoters
have misled the public on the question of the actual physical super-
iority of their preservatives. Freedom from leaching has been claimed
for metal salts which were still soluble after treating; greater depth
of penetration has been claimed for preservatives that have been found to
penetrate no farther than does creosote, and occasionally not as far;
complete protection to the very core has been claimed for treated lumber
with no more than a superficial protection; fireproofing, rodent proofing
and insect proofing has been claimed for treatments of doubtful value.
In many instances the Justifiably shaken faith of the public has been
bolstered anew with fresh financial reserves for high-pressure promotion
to get a turnover out of an unwise investment. The confidence of the
public very nearly has to be bought under conditions such as these. A
new proprietary preservative could hardly be expected to compete with
creosote and its fellow competitors without promotional backing. Hence
the claims of advertisers must be taken with a grain of salt, and
nothing should be included in a scientific report on such a product
unless it has been attested to by reliable researchers. It might not
be amiss to follow Lord Kelvin's advice in this respect: to measure
everything in order to know what you are talking about. Definite long-
time service records should be the strongest criteria by which a pre-

servative is Judged.

COPPEReMETAqARSENITE

Copper-meta-arsenite is really a cross between two major groups

'II.I[J ... .

 

 

 

 

28

of non-gaseous fungicides and insecticides. These groups are, broadly:
l. antiseptic oils; 2. coal-tar antiseptics; 3. violently poisonous
mercury compounds; h. violently poisonous cyanides; 5. copper compounds;
6. poisonous arsenic compounds: 7. sundry metal salts; and 8. the
poisonous alkaloids (as nicotine). In contrast to these, the gaseous
compounds, or fumigants, include the hydrocyanic group, naphthalenes,
tetrachlorethane, sulphur dioxide, carbon monoxide and formaldehyde.

Copper-meta—arsenite is represented in its best form by the patent—
ed basic process held by the University of California and leased to a
commercial enterpriser. Although the actual commercial processes are
secret, it was the writer's privilege to observe every detail of them
and to study the behavior of many species of wood under treatment.

Concisely, the chemical preparation involves mixing copper sulphate
solution with arsenic trioxide solution under favorable conditions in
the presence of aoueous ammonia and stabilizing compounds such as sodium
hydroxide and glycerine. The resulting preservative resists leaching
to a remarkable degree.

According to Dr. Aaron Gordong, inventor of the process, the above
mixture reacts to form a group of stable, non-soluble compounds in the
presence of water. These compounds include copper arsenite, CuHAsOB;

copper-meta—arsenite, Cu(AsO and copper hydroxide. Cu(OH)2, of which

2’2:
the first two are salts of very weak acids, hence they dissolve by

hydrolyzing to form weak meta-arsenious acid, HASO , and arsenious acid,

2

H .
3AsO3

Chemist, California Forest Experiment Station, Berkeley. California.

But c0pper hydroxide reacts with these to reprecipitate them thus;

) insoluble products.
2 HzAsOB + 3 Cu(OH)2 = 3 CuHA803+ 6 H20

In contrast, the soluble zinc-meta-arsenite, ZnAs(02)g, reacts as

follows with acetic acid commonly used to bring it into solution:

2 HACIO + znAs(og)2 - Hesso2 + zn(Ac)§°, both products soluble.

Many copper-bearing fungicides have been placed on American and
EurOpean markets under such proprietary names as "Bordeaux", “Forstite”,
"Sulphateatite", "Borderite", "Kupferpasta Bosna", "Caffaro". "Kurkakol".
"Nosperal", "Vitriolin", "Coposil" and "Chemonite".

The non-technical reader may question why cepper-meta-arsenite
(which.is injected in a water solution in the first place, and which
is made partly from soluble copper sulphate in the second) will not
leech.out of treated wood as freely as copper sulphate or zinc chloride.
It is a reasonable question, and one easily answered; First, the aqueous
solution is not water alone, but contains ammonium hydroxide; second, the
copper sulphate has lost its identity in the reactions already illustrated.
The writer has helped to prepare commercial charges of copper-meta-arsen-
its and has observed in several instances that it took five hours of
stirring in the presence of aoueous ammonia under pressure to get the
solids into solution. On one occasion when a leak developed in the
mixing tank, allowing ammonia gas to escape, considerable of the solids
immediately precipitated and were redissolved only with difficulty by

the introduction of ammonia gas.

u;

10.
(AC) represents the complex acetate radical in acetic acid.

30

It is a simple matter to precipitate the solids from liquid
solution by releasing the ammonia, but almost a disheartening task to
redissolve the precipitate which is the toxic factor. In other words,
capper-meta-arsenite mixture is not soluble in water to more than the
slightest extent. Of that much it is certain, but of other factors
such as fire resistance and rodent repulsion there remains to be done
more research before any additional claims will be upheld.

Some readers, familiar with the handling of copper sulphate as a
preservative, may auestion the cost of treating eouipment for handling
copper-meta—arsenite, since copper sulphate is so corrosive to iron and
steel11 that wood, concrete or alloys usually must be employed for its
handling. Not so with copper-meta-arsenite, for the first step, only.
involves the need for a wooden tank - that of dissolving the copper sul-
phate crystals in water. The patented process involves the subsequent
neutralization of the weak corrosive acids and the admixture of ammonia,
so that succeeding steps and transportation can be handled in ordinary
steel pipes and tanks.

Before proceeding further with a discussion of copper-meta—arsen-
ite, it is almost necessary, from the standpoint of a clear understand-
ing, to trace back the history and records of both the copper and arsenic
salts which go to make up the finished products. Copper-meta-arsenite
is relatively new, having had its birth and inception only about fifty

years ago, but the parent salts are old in history.

 

11.

Copper sulphate (bluestone, blue vitriol, etc.) is a pentahydrate,
Gus .5 0. It is soluble in water, the solution having a slightly
acid reaction which evidences itself by attacking many metals. This
acidity is probably caused by the formation of sulfuric acid. H 80h'
by hydrolysis, although some investigators say it is caused by th
formation of mono-hydrated copper sulphate, HO.Gu.O.502.OH.

31

Martin (116) says that the cuprammonium group was known in 1885
to.kudoynaud, who called it "Eau Celeste": later it was known as "Azurin".
The group is formed by an excess of ammonium hydroxide added to a sol-
Iition of copper salt, whereupon a peculiar reaction occurs. The ammonia
combines pith the copper to form a cuprammonium salt. Copper sulphate,
GuSOu, first hydrolyzes to free electropositive ions and the equi-
valent number of free electro-negative sulfate ions; next. traces of basic
c0pper’compound and free sulfuric acid, H250“, are thought to form. Added
31330111111“ hydroxide, NHnOH. neutralizes the sulfuric acid and precipitates
basic copper compound, which finally redissolves in ammonia to form deep
blue cuprammonium sulphate solution, possibly Cu(NHB)u. It then forms
negative sulphate ions and positive cuprammonium ions. It never breaks
down to free sulfuric acid again.

The earliest history of the use of fungicides and insecticides is
obscure, but there must have been much random experimenting. The first
recorded successful history dates from the accidental discovery by
Millardet in 1882 of the action of lime-cepper sulphate solution, although
Martin (116) says that Robertson used soap-vetted sulfur as a fungicide
in 1821. After the efficacy of Millardet's discovery was generally known
there came into use a myriad of materials, many of which harmed the
plants they were to protect. (The knowledge of wood-decay fungicides
grew Jointly with the knowledge of plant-disease fungicides.)

Fungicidal and insecticidal action are manifold: fungicides may
act to kill fungi outright; to stop fungus growth; to repel fungi by
chemotropic action; and to inhibit germination of spores. insecticides
may act as direct killers, as deterrents, or as ovicides to stOp the

hatching of eggs.

32

The largest and most important group of fungicides at present
(in phytOpathological use) contains as its active agent some form of
copper; and the most successful group of insecticides contains arsenic
in some form.

Arsenic salts have long been known to be poisonous to insects, but
they have been used as insecticides generally only since about the middle
of the nineteenth century. Their rise was not without obstacles to
overcome, since France passed a law in 18M6 prohibiting their use in the
interests of public safety. .After some time the arsenic group proved
so successful in the United States that the French law was repealed.
Today there is still a question in the minds of some investigators (20)
(85) (15h) concerning the liberation of poisonous arsenical gases by
certain molds on arsenic treated wood. In 1867 Markham found Paris
Green to be a dependable control for Colorado beetle, which for a time
threatened the world's potatoes. Paris Green, called "Schweinfurter Gran"
in Germany, is a complex compound of copper acetate and copper arsenite
(closely related to our copper-meta—arsenite) to which has been given the
formula (CH3000)2Cu.- 3 Cu(A502)2. It was originally made from verdigris,
which was in turn made by the action on sheet copper of the acid "marc"
or residue of wine manufacture.

Arsenious oxide (white oxide of arsenic) is obtained as a bybproduct
of the roasting of arsenical ores of many metals. It is cheap to purify
by sublimation into both the amorphous and crystalline forms, but it
cannot be kept in the amorphous condition for long, as it changes to the
crystalline form on standing. The arsenic atom is trivalent in arsen-
ites; pentavalent in arsenates.

The arsenic salts are not more than slightly soluble in pure

 

 

Ll

33'

water, but are perfectly soluble in water-solutions of carbon dioxide or
sumnoniaq precipitating when the gases escape. Both arsenites and arsenates
8113 toxic to insects, including termites, wood borers, carpenter ants and to
marine borers.

According to Fink, as reported by Martin (116), the toxicity of
arsenic is based on a lowering of oxygen consumption by poisoned insects.
That action is probably a result (of inactivation of the oxydizing en-
zymes, perhaps by interference with the normal functioning glutathione
131 the oxygen-reduction phenomenon in cell tissue. Some writers have
tittributed the trypanocidal action to the remarkable affinity of arsenic
for organic combined sulfur.

Other excellent insecticides may be mentioned in passing: lead

chromate and ground rhizomes of white Hellebore (Veratrum album L.)

 

which.were used as far back as 18h2; cuprous cyanide; cuprous thio-
cyanate; dinitro-o-cresol; dinitro-ortho-cresol; and thiodiphenylamine.

Arsenic salts, although excellent as insecticides, have not so
much to commexithem as fungicides, at least when compared with copper
salts.

Although there has been a wide variety of materials suggested for
plant fungicides, only sulfur and copper, in the main, survive for gen-
eral use. Mercuric chloride is more toxic, and ferrous sulphate, zinc
chloride and zinc sulphate are very good, but copper salts prove to be
the best all around according to most authorities.~ Silver salts are
about equal to copper salts but are expensive per unit of toxicity.
Lead arsenate is fungicidal, as is calcium arsenate, according to num-

erous authorities (M.B. Waite. W.J. Morse, H.H. Whetzel, S.E.A. McCallan,

T.C. Loh, E. Salmon and 13.5. Horton).

 

 

It.

3.1!! ..

 

 

THE AGENCIES DESTRUCTIVE TO WOOD

AND A GBBERAL DISCUSSION OF TIEIR CONTROL

31:

THE AGENCIES DESTRUCTIVE TO WOOD:

GENERAL BACKGROUND.

There is a tremendous amount of published work bearing on the sub-
Ject of wood preservation and laboratory tests related to it. The U.S.
Department of.Agriculture publishes lists relating to the field (162)
(163) which should help a beginner to survey the literature at hand.
The Superintendent of Documents at Washington publishes two excellent
catalogues (generally available in public libraries) (170) and (171),
and there is a number of technical indexes relating to current liter-
ature. Phytopathflogn the Agricultural Index, the Engineering Index,
’Journal of Agricultural Research, Chemical Abstracts, and the Review of
Applied Mycology supply nearly all the source data that any researcher may
need. In this study, the problem is not so much how to find pertinent

literature as how to select the best material from the field at hand.

SOME NOTES OR THE STRUCTURE OF FOOD

The mechanics of wood preservation and wood decay are so closely
allied to wood structure that an understanding of the basic structure of
wood is necessary before further investigation is advised.

humerous available references cover the subject of wood technology,
as (25) (3H) (5H) (98), so that it should not be necessary here to go
into more than a skeleton outline. Current work by Record, Harrar,
Brown and Panshin, Koehler, Lodewick and others may be found listed in
library catalogues and indexes.

Abies concolor, Lind. & Gord.. the species from which the white fir

 

lumber has been selected, is, of course, one of the conifers. or softwoods.

Like all other softwoods and hardwoods, its basic structure is not homoge-

35

neous, like glass, but heterogeneous (168). The wood. instead of being
a unifbrm, solid mass, is composed of innumerable cigar-shaped cells,
filled.with air when the wood is dry. The great bulk of these cells is
longitudinally disposed in the tree trunk.

There are in a softwood tree no continuous vertical tubes or vessels
to conduct the sap as there are in hardwoods: Mostliquid movement in a
softwood tree is through the membranous pits in the walls of the cells.
Since the cells are very long in relation to their diameter, it follows
that lengthwise liquid travel will be facilitated by capillarity, while
lateral liquid travel will have no such advantage, except in the small
percentage of ray-cells. (‘i.e., in our commercial lumber species).

There are certain cells radially diSposed in a tree to carry food
materials laterally between the inner bark and the internal wood. These
radially disposed cells constitute the wood rays, which in some hardwoods
like oak and sycamore, add a beautiful figure to the grain. Wood ray
cells form only a small percentage of all the cells in a tree, so that
their aid to total lateral liquid movement is not very significant.

In many trees, white fir excepted, there is a marked difference
between the outer portion of the wood and that toward the center of the
tree. Usually the outer, newer wood is light in color while the center
portion is dark. This difference in color is significant.

The center, dark wood of a tree is called heartwood (duramen in
some old texts); it is all dead, even in living trees, and it is marked
by deposits of ”foreign" substances not present when the wood cells were
first laid down by the cambium. If a wood is durable, it is these
substances which render it so, for there is no native durability in

wood substance itself. Hence only the heartwood of a tree can ever be

III. ‘9‘-

36

considered to be durable in the presence of wood-decay fungi, and that
durability may vary widely in a given species.

The outer portion of wood on a tree trunk isimmalhy'white, or only
slightly colored. This zone is known as sapwood (alburnum in some old
texts) and it contains only a small portion of living cells, those food
storage cells known as parenchyma,and the very outer layer. Sapwood
varies.in thickness between species, and even between trees in a given
species. It is never naturally durable unless it is rendered full of
resin by reason of a localized injury to a section of living cambium.

It stands to reason that the outer portion of forest-grown trees
will be the highest quality, at least on the clear bole below the crown.
Limbs have pruned themselves and the sapwood is clear and free from
knots. It is economically unsound to fail to protect this excellent
part of a tree from decay and insects after it is converted to timber
products.

In certain species of trees, moreover, neither the sapwood nor
heartwood is durable. White fir is one of these. The deposits in the
heartwood cells of white fir are neither toxic nor particularly repellent
to fungi or insects. If white fir (or any of the many perishable species)
is to be used in locations favorable to decay, it is important that every

piece be treated with a desirable preservative.

THE MECHANICS OF DECAY

As discussed in the historical introduction, the mechanics of wood
decay was not understood until Robert Hartig's time in the late nine-
teenth century. Even then, only the broad principles were seen and

understood. For the purposes of this study, however, a conception lit-

37

tle more advanced than Robert Hartig's will suffice (58).

Wood decay (known variously as rot, punk, dots and doze) is usually
described according to its physical appearance as one of a number of
kinds; viz: white pocket rot, white spongy rot, brown ring rot, yellow
ring rot, brown stringy rot, brown mottled rot, brown pocket rot, red
ray rot, brown cubical rot, and the like (20) (73)(95)(128)(162)(166).

Regardless of the type of rot - white or brown, ring or ray - it
is all caused by the same general agency, a fungus. Variations between
the different rots are caused primarily by attacks of different species
of fungi. Thus, the same species of wood may exhibit both brown and
white rots if attacked by two types of fungi.

That the structure of wood and the mechanics of decay are closely
allied is plainly seen when the difference between white and brown rots
is analyzed. Basically the difference lies in the breakdown of more
of one wood element than another: more cellulose broken down and used
as food in the case of brown rots: more lignin utilized in the case of
white rots.

The physical properties of a given wood, attacked by each of the
two broad groups of wood-rot fungi, vary widely even in the early stages
of attack. Hence the basic structural composition of wood becomes a,
factor in advanced studies on the decay problem.(21)(22)(23)(3M)(58)(7H)
(77)(132).

The cells of wood are attacked directly by the invading fungus
hyphae which are microscopic, threadlike organisms having the faculty of
yflercing the cell walls of living or dead wood, or both, depending on
the species of fungi. Although there is no general agreement on the exact
process of attack, investigators are agreed that wood-destroying fungi must

secrete a dissolving enzyme from the growing tips of their hyphae, result-

 

 

 

 

 

..
2

L

H-

!o.'

\-

{1
.-

ing in a.chemical breakdown of a small portion of the cell wall at the
point of'contact. When hyphae are present in sufficient mass, a com-
plete breakdown occurs. Almost every text on forest pathology is illus-
trated wi th photomicro graphs of this phenomenon (2’)) (29) (‘42) (57) (58) (6h)
(73)(7h)(128) and (150).

If a partially decayed piece of wood be sectioned and viewed under
the microscope, perforations in the cell walls will be observed distinct
from the cell pits. These perforations, almost always irregular in
outline, are the scars left by the penetrating hyphae. Very seldom
will fungus hyphae be observed in and through these perforations, except
on the freshly attacked wood specimens. Old hyphae either dry up and
disintegrate, or they are absorbed and drawn ahead to the growing tips
as part of the food supply renuired for growth of the fungus. Author-
ities are not fully agreed on this point.

As the hyphae of the fungi anastomose throughout the tracheids of
a softwood like white fir, they usually tend to align themselves in the
path of least resistance, parallel to the long axis of the tracheids.
The basic structure of the wood thus determines the direction of most
rapid spread of decay.

An'unfortunate phenomenon, economically, is that of the hidden
nature of the advance zone of decay which may be detected in many fungi
only with the aid of a microsCOpe and staining technique (HO)(75)(129)
(136). Since wood is often weakened severely by the initial stage of
certain decays, and since it is impossible to detect the extreme
boundaries of fungus attack with the naked eye, there is seen an added
advantage to treated wood - the certainty that no decay fungus can

attack it unknown to the property owner (70).

 

 

H. .q‘

d-tlfi

 

 

Alternate drying out and wetting will not destroy most wood fungi;
in fact Hubert (73) cites instances of decayed wood which, dried for over
seven years in a laboratory, was dampened again only to find that the
fungus revived to full vigor.

Fruiting bodies may form on the surfaces of attacked wood after
the progress of decay has arrived at the advanced point where sufficient
reserve food is available. In every case where a fruiting body (conk,
toadstool, etc.) is evident on a piece of wood, it may be taken for grant-
ed that the piece is already badly decayed near the point of fruiting.
How far the decayed zone may extend is indeterminate externally (l5)(20}
(91)(22)(53)(73).

In summary, then, it is seen that the decay of wood is the chemical
dissolution of wood lignins and celluloses by enzymes secreted by certain
fungi. The fungi reabsorb the enzymes and their dissolved organic mat-
ter for food. When both fungi and bacteria are found on decayed wood
it may be assumed that fungi are the primary organisms, and that bacteria

are secondary, working on altered wood tissue.

WOOD DECAY FUHG

Fungi are primarily responsible for the condition we know as wood
decay. In addition to being only secondary organisms on decayed wood,
certain bacteria may actually slow down the rate of decay by inhibiting
the growth of wood-decay fungi (172); others may hasten the rate of decay(20)

Without exception the wood-rot organisms are confined to the higher
fungi. A few belong to the Ascomyceteae and more to the Heterobasidiae,
but most are found in the Basidiomyceteae (Eubasidiae). It would be
effort wasted to outline mycological classification here. Numerous

references are available to cover that field (15)(39)(h2)(h7)(57)(lh5)

MO

(150) (151) (162?) (177).

Molds of woods, distinct from rots,and some stains are centered in
the lower fungi, notably in the Mucorales. Stains work normally in sap-
wood only; Although they do ramify throughout the wood cells, and enter
them as do the rots, their method of entrance and their food habits are
dissimilar. While rot-fungi hyphae dissolve portions of the cell wall,
stain hyphae seem to seek out the thin pits and to enter through them—
to dissolve and take up the cell contents rather than the substance of
the cell walls. The strength of wood bears little relation to the con-

tents of its cells, hence a bad staining by fungi such as Ceratostomella

 

sg).may'not affect the strength of a timber, whereas a barely perceptible
attack by wood-rot fungi may render a timber worthless. Mold fungi appear
to grow only on the surface of wood (139)(l62).

The color of molds and stains caused by the lower fungi may be
caused by masses of ripened, colored spores, by colored hyphae in the
mycelium, or by a slight chemical reaction. In contrast, the discolor-
ation of wood under the action of wood-rot fungi is due to a chemical
dissolution of the substance making up wood cells - augmented, in advanced
cases, by colored mycelial mats. (23)(32)(39)(72)(167).

Fungi propagate by several means, both sexual and asexual. most
effective from the standpoint of dissemination is spore production, al-
though growth in a limited area may be carried on by other means entirely.

The higher wood-decay fungi produce myriads of spores, all capable
of infecting new wood. Chief among the snore producing structures are
the large sporophores which are known variously as conks, brackets, toad-
stools, mushrooms or puffballs, depending on the species of fungus. A
single large fruiting body may produce literally trillions of microscopic

Spores (15), each fertile and capable of starting a new infection. Only

1+1

a very small percentage of the spores ever germinate and find favorable
conditions for growth. The air, almost everywhere, is charged with fungus
spores, as may be easily proved with a sterile agar plate open for a few
seconds. Wood is constantly exposed to these Spores and will be sure to
develOp decay if external conditions are favorable.

Beside the method of spore propagation, fungi may spread by broken
pieces of mycelium or infected wood. A piece of decayed wood in which
are living hyphae may serve to carry the fungus across a continent. Fungi
in dried wood have been known to revive upon dampening after over seven
years of storage in a dry laboratory (73). Contact between sound wood
and decayed wood may serve to bridge active fungus hyphae across to the
sound wood. Decay in one member of a wooden structure may spread from

piece to piece by contact.

Certain wood-destroying fungi, notably Merulius lacryman§_(Wulf.)

 

Fr., Poria incrassata (B.&C.) Burt., Armillaria mellea (Vah1.) Fr., and

 

 

Cyathus_stercoreus (Schw.) de Toni, may develop specialized mycelial
strands which stretch out along any surface and carry the living hyphae
to new sources of sound wood many feet away from the original infection.
Moisture may also be carried to dry wood by means of these strands.

The vital processes of fungi, as well as of other forms of life,
depend upon several conditions: a supply of food, water and air (although
certain forms of fungi approach an anaerobic existence, deriving their
oxygen from decomposition products). In addition,the temperature must
fall between certain definite limits to facilitate growth.

It may be seen therefore that wood decay is likely to develop in
any piece of unprotected wood which meets the moisture and temperature
conditions favorable to decay. Spores may be considered always present.

'Some retain their viability for great lengths of time and are ready to

1+2

geivninate when conditions favor their growth.

Preservatives l ke creosote, c0pper-meta-arsenite and others act
botfli to kill fungi which contact them, and to inhibit the germination of
snnores by a chemotronic action. C. Audrey Richards says, however, that
didflferent species of wood-destroying fungi vary greatly in their resist-
suuze to toxic agents. Even within a given snecies, different physio-
]xxgical strains or races exist which also show considerable variation
111 their resistance to the same toxic agent.

Moisture sufficient to promote decay in dwellings may be trapoed
111*”00d joints by capillarity, or it mav be acnuired through leaks in
{flannbing, condensation of moisture, scrubbing water, or absorption from
the soil.

The most important physiological factor in regard to either stain
fungi or wood decay fungi, at least from the standqoint of control, is
that of their habit of secreting acids and enzymes which dissolve the
food substance, and which are then reabsorbed by the fungus hyphae.

Wood preservation aims at this weak point in the fungus life cycle:
the powerful dissolving action of the acids also encompasses the ability
to dissolve a wide range of chemicals which may be harmful or fatal to
the fungus resoonsible for the secretion.

Schander, Ruhland, Barker and Gimingham worked on c0pper fungi-
cides in l90h. They all came to the conclusion that fungus secretions
may dissolve insoluble COpper. Exosmosis of this substance by hyphae
or spores brings about their death.

As early as 1896 Swingle thought that the germ tube of a fungus
is killed by c0pper absorbed from the cuticle of the host or sub—
stratum. He thought that there might have been a chemotropic action

which discouraged penetration.

113

Martin (116) believed that copper salts dissolve in the slightly
acixi secretions of fungus spores, depositing a cupric phosphate layer
cm: the spore membrane and making it impermeable. Martin proved that
coguoer on spores stops germination: cleaning with hydrochloric acid
results in renewing the power to germinate.

Actually, it takes a higher degree of toxicity to kill fungus
spores than it does to kill higher plants (8) and a higher degree
of"toxicity to kill bacteria than to kill fungi. Molds are harder
to kill than are wood-rot fungi. Concentrations of c0pper salts suf-
ficient to protect wood from decay, seldom are sufficient to protect
wood against surface molds.

Thus it may be seen that to kill fungi, a poison must be soluble
in the fungal acids. . It need not necessarily be soluble in water to
‘more than the slightest extent. In fact, solubility in water is a poor
quality, as leaching may remove all or most of the preservative before
fungi ever find other conditions favorable to begin an attack.

Wood, of itself, does not "break down.” It is stable, and will
last indefinitely unless external agencies destroy it. These agencies

include fungi. insects. marine borers, fire and mechanical wear.

MARINE BORERS

Of late years we have been hearing more and more of the danger
of attacks on marine structures by a group of organisms called marine
borers. Wood preservatives have been called upon to protect wood against
marine life as well as against fungi and insects.

Several factors have brought this question vividly to the public
mind, most prominent among them being the sudden and severe "epidemic"

of marine borers in San Francisco Bay from 1917 to 1921, when an estimated

$25,000,000 of damage was suffered by dock, wharf, bridge and warehouse
owners.

At the time of the San Francisco epidemic a commission was set up
‘by' the National Research Council to study and combat the menace, and the
«conunission made its recommendations in an exhaustive report in 192”.

Other excellent discussions of the ouestion may be found in various
<30nuaercial advertising literature (30)(97), and in several government
publications (163) (16+) (170) (171) .

Marine borers, unlike decay organisms, are quite rapid destroyers
of wood, and they may completely destroy an unprotected wood pile in from
six months to a year or more, depending on the location and the warmth
of' the waters. In the Gulf of Mexico, the tropical waters of the Pan-
anui Canal, The Hawaiian and Philippine Islands, and Guam, the Teredo
may be expected to reduce small piling to a-fragile shell in six
months time. In the colder waters of the North Atlantic and North
Pacific Oceans, the time would be increased to at least a year, and pos-
sibly four or five years.

There are two general groups of marine borers; the Molluscans,
related to oysters and clams, and the Crustaceans, related to lobsters
and crabs. The two groups are auite different in their physiological

structures and life processes.

0f the first group, the Mollusks, American representatives include
the 225329. the Bankia and the Martesia genera.

Teredo and Bankia are the most destructive of all our borers from
the standpoint of both speed and unsuspected damage. They are commonly
known as shipworms, and have been a scourge of ocean shipping for ages

past. Alexander the Great was known to have been plagued with them,

 

 

1*5

according to Pliny the Elder (123g).

Teredo will grow to a maximum length of four feet and a maximum
diameter-of one inch, although at the time of infestation the young 3315-
gfgg is only of pin-head size. Teredo and Bankia hatch from eggs, and
the larvae are free swimmers, which finally become attached to wood and
‘begin to burrow in with their hard, shell-like cases. As the borers grow,
the excavating shell remains attached to the anterior portion and grows
in diameter, too. Thus the borer becomes imprisoned in a long tunnel
of ever-increasing diameter. As the Teredo grows, it secretes a cal-
careous substance which forms a hard lining around the tunnel. Its food
consists of both minute marine life called plankton and the wood which
is excavated.

The Martesia genus is not included in the shin worms, but is clam-
like, its body being always encased in a lime shell. It is smaller than.
Teredo or Bankia, seldom attaining a length of 2% inches or a diameter
of one inch. Martesia occurs at present in American waters only on the

shores of the Gulf of Mexico.

The Crustacean borers include, in our waters, Limnoria, Sphaeroma

 

and Chelura. The Limnoria and Sphaeroma belong to the Isopoda, among
which are included the common sow bugs or wood lice. The Chelura spp.
belong to the Amphipoda which includes the common sand flea. All have
the general appearance of free moving soft insects, suggesting sow bugs
and young shrimp.

Of the Crustacea,. Limnoria is the most destructive. It occurs
over all United States coasts. Like the other Crustacea.. and unlike
the Molluscan borers, wood constitutes all the food of Limnoria. The

young hatch from eggs, but have no free swimming stage, so that the Spread

is quite slow. At maturity the Limnoria attain a length of from one-
eighth to one-ouarter inch. Its attack is external only, so that the
«damage is easily seen and appraised, and it extends only about one-
quarter to one-half inch deep. But the pounding of ocean flotsam wears
away'the riddled outer portion at the water line and continually exposes
:new'wood for the Limnoria to attack. The damage from Limnoria is in-
creased tremendously when water conditions favor a heavy increase in an-
imal life. That these conditions may come about through changes in
sewage disposal, industrial waste disposal and changes in current is
‘well known. .Attacks in San Francisco Bay were experienced suddenly,
after years of seeming immunity.

The Sphaeroma is larger than the Limnoria, often reaching a length
of one-half inch and a width of one-quarter inch, but it is not so prev-
alent as a rule. It produces one-half-inch burrows.

The Chelura, which is a member of the Amphipoda, does not occur in
our North.American waters. It is found in the warm,tropical waters of
the Canal Zone and around our tropical possessions.

Creosote has generally been conceded to be a dependable marine
borer safeguard, although it has failed in many instances in San Fran-
cisco Bay against the ravages of the Crustacea.. according to Atwood
and Johnson's "Marine Structures" (Wash: Natl. Res. Council. 19214)12
The writer has observed creosoted piles in the Bay area with the cen-
ters completely riddled by Teredo, so that only a thin shell remained.
Entrance was gained through the creosoted shell, which was, however,
little damaged in itself. Only the heaviest injection of creosote ser-

ved to protect piling in these waters, but heavy injections did prove

 

12.
Report of the Committee on Marine Piling Investigation, National
Research Council, Hashington, D.C.

M7-

effective.

Matched piling treated with COpper-meta-arsenite was observed (in
comparison) to have survived over eleven years of constant exposure with-
out attack by any of the borers. The only large dock installation of
copper-meta-arsenite-treated piling13 of which the writer is aware, has
not yet been in service long enough to show conclusive evidence of its
marine borer protection.

As with fungus control, the basic principle in marine borer con-
trol is the killing of borers by rendering their food poison. The preserv-
ative must be sufficiently soluble in the digestive juices of the borer
to result in toxic quantities being absorbed, but in this application
above all others the solubility must not be such that the preservative

would leach out in water.

TERMITES
A group of insects responsible for tremendous losses in the
'United States is that known as "white ants" or termites. The common name
of "white ant" is a misnomer, for the termite is neither an ant, nor is
it always white. Termites are, in fact, more closely related to roaches
than to ants. They live in colonies like ants, with definite castes
of workers. soldiers and reproducers, but there the similarity ends.
Termites are found all over the United States, but particularly
in four areas: the South Atlantic States, the Gulf States, the Southwest,
and the Pacific Coast. They attack all kinds of wood and wood products,
from wooden dwellings to bridges, telephone poles and vineyard stakes.
Dr. Thomas E. Snyder (1h?) estimates that they are responsible for an

annual 1098 of over $U0,000,000. In many sections of California the

' Private dock of Henry Kirchmann, Berkeley, California.

 

 

IE1.

by;

MS

termite has infested nearly 100% of all the unprotected wooden structures,
a condition which the writer can verify at first hand through nearly six
thousand miles of official travel in the area.

It is reported that there are over two thousand Species of termites
throughout the world, and fifty-six species in the United States. (In con-
trast, Europe is reported to harbor only two species.) There are, broadly,
three main groups of termites which live and work under characteristic
environments: 1. Subterrzuuaan or soil inhabiting; 9. Dry wood, and 3.
Damp wood termites. Each group is distinct enough to reouire different
methods of control, but all termites have life histories and habits that
show considerable similarity (M3)(60)(97)(99)(lu7)(153).

Concisely, a single pair of king and queen termites start a new
colony, and no other reproducers will be found in that colony until
after the death of the original king or nueen or both, or at the time
of seasonal flight migrations.

The eggs, laid by the oueen, hatch to nymphs which develop by
stages involving the shedding of successive skins. In two groups the
workers responsible for actual damage to wood include only the young
nymphs in their earliest stages of metamorphosis, while in the subter—
ranean group a permanent worker class is maintained.' Some nymphs ma-
ture to the soldier or guard class with enormously developed heads and
mandibles. (The soldiers are sterile, wingless, colored and blind;
some species develop soldiers which fight by secreting a sticky fluid).
The size of mature termites varies from one-Quarter inch long in the
- subterraziean group, through one-half inch for the dry wood group, to
a.maximum of three-quarters inch for the damp wood order.

All termites eat wood substance as a main item of diet, but

they cannot digest wood without the help of one-celled intestinal

1+9

Protozoa (and other bacteria and fungi) which secrete enzymes for the
digestive process. The mandibles of termites look small and weak, but
they suffice to bite off innumerable tiny pieces of wood._

.After a sufficient length of time, when the successive growth
transformations have occurred, termites are found to develop wings and to
be able to fly for a short period of time. Swarms of flying alates (the
sexually mature, winged forms) may be seen about April or May, although
on the Pacific Coast another swarm usually occurs after the first warm
fall rains. The alates fly for varying distances, possibly up to
several miles in a wind, and shortly descend to the ground where their
wings drop off, they find mates, and crawl into places of concealment
to consummate their mating and establish a new colony.

Very few swarming alates survive these mating flights; those which
escape birds have still to find a mate and favorable location for a new
colorwn (Winged termites, or "flying ants", are poor fliers, lacking
maneuverability).

Termites, like the Molluscan marine borers, invade wood for a two-
fold purpose: to gain shelter and to utilize the wood for food. The
nymphs cannot stand eXposure to strong light, high temperatures or low
humidities, consequently timbers are always excavated to a hollow shell.
External evidence of termite damage may be entirely lacking and unsus—
pected until an increased load on a timber or board causes it to fail.
Termites have many natural enemies, and if they do make an opening from
their galleries, they cuickly close it with a pasty substance.

Termites eat each other's partially digested excreta, cast-off
skins, sweet secretions, and their dead fellows. In addition they

constantly groom each other in the colony - a habit called trophallaxis -

50

for a purpose thought by most investigators to be directed toward per-
sonal sanitation.

Several investigatorslu have been able to kill an entire termite
colony by dusting one termite with arsenic trioxide. Successive groom-

ing, or trophallaxis, accounted for the deaths of the balance of the

colony.

SUBTERRANEAN TERHITES inhabit the soil, and attack wood only in the
soil or in contact with it, except under conditions where the termites
build their own contact galleries. Unlike the dry wood and damp wood
termites, these have a definite worker caste.

Like other termites, these shun light and low humidities, hence
their work is seldom in evidence until a failure occurs. Sometimes,
however, the contact tubes may be seen in semi-hidden locations, or
seasormfl.f1ight swarms may give evidence of attack. The subterranean
termites have been officially reported in every state in the Union
except North Dakota, and it seems probable that they will be found there.

In the United States at least eight species of Reticulitermes,

 

and one lone species of Heterotermes (in the Southwest) have been re-

ported.

DRY WOOD TERMITES are entirely wood inhabiting. They need very little
mOiStuTels to carry on their life processes, and they enter wood directly
from the air at swarm periods. Points of entry include checks, cracks
and open joints in pieces of wood or in dwellings.

These termites form fecal pellets and discharge them periodically

u

1h.

1‘3.
' Hunt and Garrett (85) estimate that dry wood termites will work
in wood of 10 - 12 % Moisture content or higher; no upper limit is noted.

Including Schrader of the University of Washington.

5L

-frorztemporary openings, which habit often serves to indicate their
‘presence.

Only one genus, Kalotermii, is represented in our country. It
is found only in a narrow strip across the southern tier of states and
Imp both.coasts, as far as Virginia and Central California. It is much
less injurious than the subterr an ean group, and reouires several years
to do appreciable damage.

Subterrannean termite damage is often incorrectly appraised as
dry wood termite damage when the manner of entry is unknown. Upper

floor damage in dwellings has often been traced to direct contact

with.the soil through hollowed grape vines, wistaria, Virginia creeper,

and ivy.

DAifl’ WOOD TERflITES, like the dry wood group, reouire no contact with
the soil, but they must have wet wood to continue their operations. In
almost every instance the wood will be found to be decayed as well as
wet, but whether the damp wood termites select decayed wood or cause it,
is yet to be determined. It is known, however, that their operations
do extend into sound wood.

This group belongs to the genus Zootermopsis (or Termopsis), and
it is found only west of the Rocky Mountains, usually in damp forests.
Occasionally wet wood termites extend their work into buildings from
an old decayed stump left under a house, in contact with foundation
members.

Very few native woods offer much resistance to termites. The
heartwood of redwood, cypress, Port Orford cedar, and some very resinous
pines has shown marked resistance, but at times even these Species are

attacked severely. Termites will work in the sapwood of any species.

 

q.fi(.~ ‘Iu!

 

l.‘

 

52.

Preservatives may act to kill the termites outright, to kill the

furugi in the termite galleries,16 to poison the Protozoa in the termites'

imitestines, or to discourage the termites by rendering the wood unpal-
ata‘ble.

Heavy injections of creosote accomplish these purposes, as do
various arsenic salts. Copper-meta-arsenite has proved itself a ter-
rmite resistant treatment for wood, but only in the zone penetrated.

Termites may bridge over treated wood, or enter the center, un-

treated portions of timbers which have checked or cracked deeply.

POWDER POST BEETLES include several genera of beetles which are respon-
‘sible for a tremendous amount of damage to wood products in the United
States.

Adult beetles either bore holes in wood or bark to deposit their
eggs, or they utilize natural openings such as pores in the hardwoods.
The larvae, or grubs, hatch from the eggs and begin to bore into the
wood for food and shelter. They leave behind, as they bore, a fine
powder which consists of undigested wood particles. Usually the pres-

ence of wood borers is indicated by this dust or powder which falls

out of the small openings.

In time a metamorphosis occurs, pupation beginning in the early
spring, and the adults bore holes to escape in late spring or early

summer. They repeat the life cycle in other pieces of wood, or even

in the same piece.

The worst beetles, from the standpoint of total damage, are in

the genus Lyctus, which occurs all over the United States. They concen-

trate their operations on hardwoods with large pores such as the oaks,

16

' Some investigators believe that termites cultivate fungi to use it
for their protein intake - a vital dietetic factor.

 

 

 

 

53

ashes and hickories, but they also attack maple, walnut, persimmon,
elm and sycamore.

Since the starch content of the wood seems to determine its lia-
bility to attack, most of the damage occurs in the sapwood. More dam-
age occurs in fast dried wood than in very slowly dried material. Kiln
dried furniture woods are often seriously damaged by these beetles, as
are untreated interior trim and flooring.

The arsenic component of cepper-meta-arsenite is the active con-

trol factor in beetle protection.

CARPENTER.ANTS are true ants which excavate wood in contact with the
soil, but they do not utilize the wood for food. Their excavations
serve for shelter only, and may be easily distinguished from termite
lexcavations because carpenter ants maintain absolutely clean galleries.
Termites leave pasty excreta, frass or pellets in their workings.

Carpenter ants prefer to work in springwood of posts, poles and
timbers that are already partially decayed. They take years to do any
appreciable damage. Copper-meta-arsenite will control them two-fold:
first, it will prevent decay, a condition which they prefer; and,
second, it will kill the ants which excavate in the treated wood.

For every living agency of wood destruction the same fact holds
true —- that exterior protection alone is not the final answer. Wood
is too prone to check or crack, exposing the inner, untreated portion.
When that is the case, any one or all of the agencies can proceed to
attack the inner portion without harm from preservatives in the outer

shell.

FIRE is one of the major factors in the destruction of wooden products.

 

JA’I.IIt

ll .l. .

5‘

 

 

5h

but it has been capitalized to excess in the claims of commercial pre-
servatives.

No preservative on the market today is fireproof, but some are
fire resistant, at least to a degree. In the quantities in which metal
salts are injected into wood, there could be very little pronounced
fire resistance. On the other hand, certain widely used metal-salt
preservatives would actually harm wood if they were present in suffic-
ient quantity to prevent burning.

Oily preservatives, such as creosote, actually add to the heat of
combustion when a treated timber burns. Creosoted timber, in addition,
produces an objectionable, dense black smoke when burning.

Proprietary compounds as a whole offer advantages over creosote
from the fire standpoint, but mostly in the fact that they do not add
to the heat of combustion. Their fire resistance is usually far over-
rated. For a complete discussion of this problem, see the files of
the Annual Proceedings of the American Wood Preservers' Association (M);
Hunt and Garrett (85): Prince (125): Truax (158)(159); and the technical

indexes and catalogues in public libraries (170)(171).

LABORATORY METHODS OF PPESERVATIVE ESTING

55

LABORATORY METHODS OF PRESERVATIVE TESTING

There are three general approaches open to the experimenter by
which the comparative preservative value of a given chemical may be de-
termined: first, by putting full-size wooden timbers in ordinary con-
struction and watching them to see how they compared in durability with
matched untreated timbers, or by using smaller pieces of the same mater-
ials exposed to more severe natural rotting conditions; second, by
carrying on the test in the laboratory, using equipment which would rot
treated wood under optimum conditions; and third, by growing wood-rotting
fungi on artificial media with varying concentrations of preservatives.
(9)(10)(20)(“2)(u9)(50)(59)(131)(135)(1h2)(172)(176). Snell (1M3) gives
an unusually clear discussion of the problem.

The first broad test method is too slow and cumbersome for the
tempo of our times, except for poor preservatives on the least durable
wood species. It is, however, the truest test of the value of a pre-
servative or the relative durability of a species, showing in from one
to fifty years what might actually occur under ordinary service con-
ditions in about the same time. The third method is too theoretical
to rely upon without practical substantiation.

The second method, although artificial, is probably most often
employed by researchers in the field, giving results in from one to six
months that would require up to ten times that many years under natural
conditions. The accelerated results may or may not indicate what can
be expected in service; several investigators using the same technique
may disagree on their findings because wood and its treating are so
variable. Nevertheless, the American public is attuned to a tempo of

living and working which demands speed in everything - in development,

in production and even in research - hence the almost universal accept-
ance of the fast, variable, non—standardized laboratory technioue of
testing (1M2).

Photography and increasing dissemination of technical Journals have
aided much in the gradual trend toward the standardization of technique,
but the goal is yet to be reached. It is, of course. impossible to
standardize every variable because of the heterogeneous nature of wood
itself and the uneven depths of penetration in even a single piece of
timber.

Taking the matter of the test fungus alone, considering tests with
a single fungus, there are today advocates of at least a half dozen fun-
gi to be used against an array of wood species, wood preservatives or
concentrations of one preservative. The Forest Products Laboratory
at Madison, Wisconsin, recommends strongly their strain of test fungus
No. 517, an unidentified isolate from a decayed mine timber (133). The
Western Pine Association Research Laboratories in Portland, Oregon17,

have based considerable work on tests with Lenzites trabea_(Pers.) Fr..

 

an active dry-rot fungus encountered in actual service conditions. In

some European laboratories Merulius lacrymans (Wulf.) Fr., vies for first

 

honors, being a troublesome timber destroyer on the European continent.

Poria incrassata (B.& C.) Burt., Coniophora cerebella Pers., and others

 

 

are preferred in some laboratories in this country for the reason that
they are common, either here or where our timber is shipped.

All the fungi named have their merits from one standpoint or
another, whether it be that of actual danger of attack by them under

natural conditions: that of broad adaptibility to wood species (102)

17' Wood decay studies directed by Dr. Ernest E. Hubert.

57

and conditions; that of rapidity of growth and attack (172); or that

of ease of growing and propagating the fungi in pure culture in the lab-
oratory. Some fungi attack lignin most strongly while others seem to
concentrate on wood cellulose; some attack softwoods and some prefer
hardwoods (102). Factors such as these may determine the choice of
organisms.

Some investigators prefer the use of Petri dishes for culture work
while others, with equally good reason, prefer the use of Kollé flasks.
Each type of culture chamber has its peculiar advantages (109)(1M2)(l75).

A great volume of literature covers the subject of preservative
testing, and many investigators have devoted their time to studies in
the field. Bateman, Findlay, Fleming, Harsch, Hatfield, Hirt, Hubert,
Humphrey, Kaufert, LaFuze, Long, Reeve, Richards, Schmitz, Snell and
Waterman have covered the technique quite thoroughly. 566 citations
(9)(10)(11)(u9)(50)(51)(52)(63)(59)(73)(80)(81)(83)(96)(102)(109)(131)
(135) (1M2) (1‘6) (163) (172) (176) .

One of the most significant steps toward standardization of tech-
nique in the field was taken in Missouri in December, 1929, when a

group of interested workers18

headed by Henry Schmitz met to discuss
the problem (lh2). Although no clear-cut standards resulted from the
meeting, considerable progress was made.

Two broad testing systems are extant, the American and the EurOpean.
In the American system fungi are cultured on agar with various concen-

trations of preservative to find the total inhibition and killing points.

Every fungus shows different points with the same preservative, making

 

18' The group included E.E. Bateman, R.H. Colley, S.R. Church, Carl
Hartley, E. Waterman, AoL. Kammerer, H. von Schrenk, E.B. Fulks, E.E.
\Rubert, C. S. Reeve, 1.3. Snell, C.A. Richards, D.E. Linder, J.D. Burnes
and Henry Schmitz.

58

it necessary to compare different chemicals against the same organisms.
Madison No. 517 is often used.

The European method relies on tests involving treated blocks of
pine sapwood, with a matched untreated test block. The small wood

cubes are laid over a fungus mycelium mat on agar and allowed to re-

main for an arbitrary period.

GVYERAL PROCEDURE

iELECTION OF WOOD
In order to eliminate the human element as far as possible, it
‘was decided to select commercially treated lumber rather than to treat
the lumber by hand. Accordingly, the lumber yards of the Diamond
thatch Co. at Stirling City, California, were used as a source of supply
‘for treated wood. In September, 1937, random samples of commercial

2"xh" white fir sapwood (Abies concolor, Lind. & Gord.) were cut by the

 

‘writer from mid-sections of treated full-length scantling, and brought
to East Lansing, Michigan.

The surfaced 2"xu" material varied in ring count from six to
twelve rings per inch.

From the same lumber yard, untreated 1"xu" white fir strips were
taken for check samples. Every piece in the yard was of the current
year's sawing, sound and air-dried.

At East Lansing the samples of lumber were sawed into about
1/8" thick cross-sections which were numbered with pencil consecutively
from 1 to 36, with a key letter preceeding, as Arl, A-?, 3-1, B-2, etc.

After sawing and numbering, the sections were bound together in
packets of similar key letter and allowed to come to equilibrium in
a closed box in a warm inner room of the Plant Pathology Laboratory.
After two months several specimens of each bound set were weighed care-
fully, dried in an oven at 212°F., and weighed again. The loss in
weight, expressed as a percentage of the oven-dry weight of the sample,
was taken as the initial M.C. (moisture content) of each piece. The
several M.C.'s were then averaged together and that figure was used as

the average H.C. for the packet.

60

Using the average M.C. as a basis, oven—dry weights were calculated

for each numbered wood wafer, and recorded for future reference.

SELECTION OF GLASSRARE

Early in the experiment it was decided to use the so-called Europ-
ean system of preservative analysis and rating. For an authoritative
evaluation of this and other methods of procedure see Schmitz (lh2), Hunt
and Garrett (85), Riker and Riker (136), Boyce (20), Richards (135), and
Long (109). Dr. Ernest E. Hubert, of the Western Pine Association Lab-
oratories in Portland, Oregon, had shown the writer the advantages of
the cotton-stoppered K0115 flask some time before.

Thirty Pyrex Kollé flasks and one hundred Pyrex test tubes were
made available for eXperimental use, together with other necessary

equipment for mixing media, making transfers and sterilizing.

SELECTION OF CULTURES
0n the written advice of Dr. RUbert, the following wood-rotting and
wood-staining fungi were selected for the study:

1. Poria incrassata (B.&C.) Burt. (78)(79)

 

2. Merulius lacrymans (Wulf.) Fr.

 

. Lenzites trabea (Pers.) Fr.

 

. F.P.L. Madison No. 517 (133)

 

. Lentinus lepideus Fr. (17M)

 

. Coniophora cerebella Pers.

 

3
h
5. Trametes serialis Fr.
6
7
8

. Graphium rigidum (Pers.) Sacc.

 

9. Ceratostomella pluriannulata Hedg.

 

10. Certostomella pilifera (Fr.) Hint.

 

61

A request for cultures of each fungus was directed to Miss C.A.
Richards, Pathologist of the Forest Products Laboratory at Madison, Wis-
consin. (Miss Richards maintains the public stock of wood attacking
fungi for the United States Department of Agriculture.) All were furn-
ished except 2 and 7, which Miss Richards was unable to supply.

Later in the study several additional fungi were tried in a lim-

ited way. These included Cyathus stercoreus (Schw.) de Toni (172),

I

 

Chaetomium sp., Penicillium sp., Armillaria mellea (Vah1.) ex Fr., Asperg

 

 

 

gillus sp. and £222: sp.

With this selection of organisms it was possible to determine the
inhibiting or killing action of copper-meta-arsenite on typical mold-,
stain-, and wood-rot fungi.

Stock cultures of the various fungi were kept growing on malt
agar in test-tube slants by transferring to fresh agar slants as the
preceding ones began to dry out after one to two months. Later in the
study it was found that test tube cultures could be kept almost indefin-
itely without transfer by sealing the cotton plugs with a skin-like
product called Parafilmlg. Even aerobic fungi seemed to grow about as

well when sealed as when unsealed, although the moisture was kept from

escaping for as long as a year.

EXPERIIENTAL PROCEDURE

Malt-agar mediawere prepared according to advice from Miss C.A.
Richards. From 1.0% to 2.5% bacto-agar, and from 1.0% to 2.5% Trommer's
liquid maltgO were tried with little variation in the growing rate of

fungi. Higher concentrations of bacto-agar were found to be desirable,

 

19' Made by the Menasha Products Co., Jenasha, Wisconsin.
20. The Trommer Company, Fremont, Ohio.

4.5.Ibum. .....I...

 

62

however, in that less media breakdown occurred. (The necessity for care-
ful sterilization of agar resulted in several cases of advanced temperature
breakdown. Although the fungi would grow well on liquid media, the tech-
nique employed in this study would not accommodate it) (109).

Sterilization of Kolle flasks and media was effected with an auto-
clave run at approximately seventeen pounds of steam pressure.‘ Tempera-
hires at over twenty pounds of steam often were sufficient to break down
the agar completely. Even at seventeen pounds pressure, partial break-
down sometimes occurred, and it was necessary to let the flasks sit hot
for about twenty minutes to allow the precipitate to settle. If this
were not done, the flocculent precipitate would interfere with the de-
tection of contaminants in young cultures.

The concensus of opinion among laboratory technicians is that sev-
eral intermittent heatings at about twenty-four hour intervals are more
efficacious in sterilization than is one equal, prolonged heating.
Intermittent heating allows heat-resistant spores to germinate between
successive heatings and to become sensitive to high temperatures.

After sterilization, the agar plates were carefully inoculated in
several places from the stock cultures of fungi. Gummed labels were
marked, placed on the necks of the flasks and covered with Parafilm to
prevent loss of legibility. While the inoculated areas grew, the plates
were watched carefully for evidences of contamination.

Efforts to remove contaminants proved fruitless. Attempts were
made to lift out contaminated areas bodily;.to burn them out with red-hot
spatulas: to kill the contaminants with alcohol, mercuric bichloride,
carbolic acid and copper-meta—arsenite. None proved entirely successful.

The mechanical method was unreliable; it seldom caught all the contamin-

 

 

.i-lv-

ants. The red hot spatula served to Spatter spores or pieces of agar
and hyphae. Alcohol in any concentration seemed only to inhibit tempor-
arily the growth of foreign fungi and bacteria. The several poisons
made permanently sterile areas on the agar plates. If contamination
were found to occur, it was deemed best and fastest to start over again
'with a new culture. '

After several days to a month (depending on the species of fungi)
the several inoculated areas coalesced to a single mycelial mat which
covered the entire surface of the agar. When this had occurred, ster-
ilized wood wafers were laid flat on the mycelial mat and allowed to
remain undisturbed for the test period of from two to eight months,

For wood sterilization, it was decided to use the method suggested
by Schmitz, von Schrenk and Kammerer (lhl, page 68). This method employs
boiling water entirely, rather than an oven, and it is much more flexible
and desirable from many standpoints than the oven sterilization method
described by Hirt (69):

Hirt oven dried one-inch cubes of locust wood at lOMOC. until they
reached a constant weight. Then they were left twenty-four hours longer

in the oven to kill fungus Spores. Next the cubes were placed in cold,
sterilized water and aspirated for two hours, after which they were allow-

ed to soak for sixteen hours more. Finally the sterilized wood was put
into culture flasks over mycelial mats, and left for the duration of
the test period.

Schmitz, von Schrenk and Kammerer found it much simpler, faster
and more satisfactory to sterilize wood wafers for decay resistance
tests by eMploying boiling water and dipping the specimens into it inter-
mittently for only a few seconds. They report the method effective in

a vast majority of cases.

6%

The experiment described in this pa)er followed the water steril-
ization technique with entire success, after several simple tests were
made to determine just how much immersion time was required to insure
complete sterilization of the wood. Plate 1, Figure 1, shows the rank
growth of fungus hyphae growing from an unsterilized wood specimen placed
on malt-agar media. Figure 2 shows the result of insufficient immersion
time -- bacterial growth in evidence although all the fungus spores were
killed.‘ Intermittent dipping which totalled about fifteen seconds in
rapidly boiling water was sufficient to kill all fungi and bacteria pres-
ent.

When the first test series was conducted, full cross-section wafers
were employed intact, with the outer zone of treated wood surrounding an
inner untreated core comprising about half the area of the section.

It was apparent that if the copper-meta-arsenite were soluble in
hot water, then not more than a few pieces of wood could be sterilized
in the same water without the possibility of partially treating the cen-
ter core. Subsequent leaching tests proved that only minute quantities
of metal salts leached during the few seconds of sterilization, but no
more than three pieces were sterilized in the same water, regardless.

The cross sections of untreated 1" x h" white fir sapwood used as
check samples were always sterilized in a separate beaker of distilled
water. No limit was placed on the number of pieces which might be steril—
ized in the same water.

As each treated and untreated sample was sterilized, it was allowed
to cool for a few seconds, and then was quickly transferred directly onto
the mycelial mat of one of the culture flasks. (If laid on too quickly,
the high temperature served to kill the mycelium under the test specimen

or to melt some of the agar. In some cases the Specimens sank so

65

(ieepdy'into the agar that the moisture content of the wood remained
too high for fungus growth.)

The Kalle flasks were plugged again and the cotton stoppers were
sealed with Paradlm to retard drying out. This method of sealing
(notton plugs with Parafilm proved highly successful, for it dispensed
with the need for exoensive humidity chambers. Cultures were kept in
rmoist condition for as long as a year in the dry atmosphere of an in-
side laboratory.

Near the close of the first test series it was found that certain
ftumgiel sent their hyphae out through the damp cotton plugs (kept damp by
the Parafilm), under the Parafilm seal and onto the paper labels. The
cellulose of the labels was attacked and several of them were rendered
illegible.

Subsequently all labels were affixed near the bottoms of the flasks
rather than near the necks where fungus hyphae could reach them. Incom-
plete eXperiments indicated that preservative treatment of the cotton
jplugs (as with a volatile—solvent preservative such as Permatolzg) would

discourage fungi from working in the plugs. Poria incrassata was found

 

in several cases to have reduced the untreated plugs to a pulpy, sodden
mass, impossible to remove in one piece or to replace tightly.

When the visual evidence of the first series was reviewed, it was
apparent that the central cores of the treated wood were affected as
much as the untreated check samples. It was then decided to collect
further data of a quantitative nature, comparing the loss in oven-dry

weight of the treated zone to that of the inner core. The boundary be-

 

22.

 

 

Formula developed by Dr.E.E. Hubert.

66

tween treated and untreated zones was arbitrarily set as the limit of
visual penetration.

As already described, the average moisture content for each packet
of wood wafers had been determined at equilibrium weight, so that oven-
dry weights could be calculated for each wafer at any given air-dry weight.
.Assuming that the moisture content was equal throughout each wafer (the
'wafers had been sawed and kept in a closed box for a year prior to the
assumption) separate weights were taken for the outer treated zones and
inner untreated cores after they had been separated with a sharp knife.
Oven-dry weights for each were calculated, using the ratio between zone
weights to divide the total for the entire wafer..

Loss in oven-dry weight was calculated after the experiment, and
recorded for each zone of each wafer. No quantitative data, of course,
could be taken for the several stain fungi and mold fungi which do not
destroy the basic wood structure.

When each culture was judged to have worked upon the wood for a
‘sufficient length of time to produce an appreciable loss in oven~dry
weight, or an appreciable stain, the culture flask was opened and the
wafers, or parts of them, were removed carefully. Adhering mycelium
was gently scraped off to allow a thorough inspection of each specimen.

Several of the earlier cultures were sterilized in an autoclave
before opening, but the heat had melted the agar and browned the adher-
ing hyphae so that inspection of the specimens was unsatisfactory. All
subsequent cultures were opened unsterilized.

After inspection, the specimens were allowed to air dry for about
two days in individual half sealed letter enve10pes marked with key

numbers. Oven drying followed at a temperature of 100°C. until the

weight became constant. It was necessary to handle the decayed
specimens very carefully to prevent loss of fragments or mixing of

them; the envelopes proved a convenient aid.

67

 

 

RESULTS

68

.69

"A" SERIES EXPLANATION

The "A" series represents wafer-like cross sections of a
two-by-four scantling of white fir, commercially treated with copper-
lnetaparsenite. The preservative treatment was only partially effect-
ive, so that the center portion of the scantling remained untreated.
.Annual rings averaged eight per inch.

Specimens A-2 to A-Zl, inclusive, were tested in one piece, and
only one weight computation was made on each.

Specimens A-22 to A-3u, inclusive, were cut to separate the vis-
ible penetration zones from the uncolored central portions. Each part
of each specimen was weighed separately, and tested under identical
conditions.

Five specimens were oven dried to determine the average moisture
content of the series, which equalled 7.7571. (-.06 to «0853). From
the average moisture content and the air—dry weights of each wafer,
oven-dry weights were computed. These weights have been shown singly
from A-2 to A-21, and doubly from A—22 to A-3h. In the latter case, the
top number indicates the weight of the center portion, while the low-
er number indicates the weight of the outer, treated portion.

Actual oven-dry weights were taken for the respective parts after
the elapse of the test periods, and the theoretical losses in oven-
dry weights are shown in per cent of the computed values. Percentages

less than 0.05% have been dropped as insignificant.

70

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72

"B" SERIES EXPLANATION

The "B" series represents wafer-like cross sections of a two-by-
four scantling of white fir, commercially treated with copper-meta-
arsenite. The preservative treatment was only partially effective, so
that the center portion of the scantling remained untreated. Annual
rings averaged six per inch.

Specimens 3-3 to 3-10, inclusive, and specimen 3-19 were tested
in one piece, and only one weight computation was made on each.

The remainder of the series was divided with a knife to separate
the outer, treated zone from the uncolored central portion. Each
part was weighed separately to obtain comparative resistances of the
treated and untreated parts of the same specimen, tested under ident-
ical conditions.

Six specimens were oven dried to determine the average moisture
content of the series, which equalled 7.78% (-.07 to +.OS§). From
the average moisture content and the air~dry weights of the parts of
each wafer, oven-dry weights were computed. These weights have
been shown singly for 3-3 to 3-10, and for 3-19. For the remainder,
the weights are recorded doubly, the top number indicating weight of
the center, untreated portion, and the bottom number indicating weight
of the outer, treated portion.

Actual oven-dry weights were taken for the respective parts after
the elapse of the test periods, and the theoretical losses in oven-
dry weights shown in per cent of the computed values. Percentaé’es

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75

"C" SERIES EXPLAEATION

The "C" series represents wafer-like cross sections of a
two-by—four scantling of white fir, commercially treated with copper-
meta-arsenite. The preservative treatment was only partially effect-
ive, so that the center portion of the scantling remained untreated.
Annual rings averaged twelve per inch.

Specimens C-M, 0-5, 0-9 and 0-26 were tested in one piece, and
only one weight computation was made on each.

The remainder of the series was cut up to separate the visibly
penetrated zones from the central, untreated portions. EaCh part of
each specimen was weighed individually and tested under identical
conditions.

Six Specimens were oven dried to determine the average moisture
content of the series, which equalled 7.75321 (--.06 to +.06§3). From the
average moisture content and the air-dry weights of the parts of each
wafer, oven-dry weights were computed. These weights have been shown
singly for C-h. 0-5, 0-9 and 0-26. For the remainder, the weights
are recorded doubly: the top figure indicates the weight of the center
portion, and the bottom figure indicates the weight of the outer,
treated portion.

Actual oven-dry weights were taken for the respective parts
after the elapse of the test periods, and the theoretical losses in
oven-dry weights are shown in percent of computed values. Percentage

less than 0.05% have been dropped as insignificant.

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78

"D" SERIES EXPLAEATION

The "D" series represents wafer-like cross sections of an
untreated one-by-four strip of white fir sapwood. Annual rings
averaged eight per inch.

The "D" series was used as a control for twenty tests, with
matched treated and untreated specimens exposed to decay fungi and
stain fungi. Some of the specimens were used for independent tests
in Petri dish cultures.

Four specimens were oven dried to determine the average moisture
content of the series, which equalled 7.76% (-.06 to +.07%). From the
average moisture content and the air-dry weights of the wafers, oven-
dry weights were computed.

Actual oven-dry weights were taken for each wafer after the
elapse of the test periods, and the theoretical losses in oven-
dry weights are shown in percent of the computed values. Percentages

less than 0.05% have been dropped as insignificant.

79

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80

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81

PLATEI

RESULTS OF TESTS ON THE EFFICACY OF WATER STERILIZATION

 

FIG.1 FIG“?

Fig. 1. Uneterilized wood wafer on agar, showing fungi and bacteria.

Fig. 2. Partially sterilized wood on agar, showing only bacteria.

52

PLATE II

EXTREME VARIATIONS IN CHEMOTROPIC RESISEANCE OF COPPERPMETAPARSENITE

 

 

Fig. 1 Fig. 2

Fig. 1. Madison No. 517 rapidly attacking untreated white fir (right)
while mycelium is repulsed by treated white fir (left).

Fig. 2. Poria incrassata growing luxuriantly on both treated (right)
and untreated (left) white fir.

 

83

EXPLANATION OF PLATE III

Plate III is nearly self explanatory; it shows graphically the
extremes of damage that were observed on copper-meta-arsenite treated
white fir, especially in the center, unpenetrated portions.

Decay actually extended into the treated zones, usually where

the color was lighter. In the case of Poria incrassata, however,

 

even heavily treated portions were finally attacked, after the decay

had developed to an advanced stage on the untreated portions.

 

HHH Edam

 

DISCUSSION

 

 

 

 

 

85

DISCUSSION

The data gathered in this experiment do not readily lend themselves
to more than cursory statistical analysis.

variables have crept into the work despite previous efforts to an-
ticipate them. One of the most significant variables was that of mois-
ture content of the wood under actual test. While some specimens became
water soaked in the culture chambers, others remained below the point at
which decay is inhibited. Several investigators have cautioned against
the use of Kolle flasks for that very reason, but it appears that the
trouble could largely be overcome by raising the specimens above the agar
on glass rods or blocks. The moisture absorption is facilitated by con-
tact between the wood and agar, or thin myselial mat.

On the other hand, raising the wood specimens above the mycelium
will necessarily result in a lengthened time until the inception of actual
fungus attack. The writer is striving toward a goal of standardized
technique, in which speed of testing is one of the major objectives.
Industry demands it, and if we are to save our markets from the compet-
ition of durable foreign woods (71)(130), we must give industry a good
rapid method of determining relative durability of new species or of
treated familiar species. Absolute accuracy would not be necessary in
such work, but results should be reasonably dependable.

The experimental data do, however, point to certain significant
trends which should be emphasized.

A comparison of results from matched treated and untreated speci-
mens, exposed to identical fungi and conditions, shows a trend which
is unmistak-able.. Unfortunately, the data do not tell the story as
graphically as would photographs, but the trend is clearly evident:

'(the following wood wafers have been tested intact.)

86

Concise comparison of treated and untreated white fir, exposed to fungi:

treated

 

A—3 - T. serialis --- 270 days ~-- 3.7% loss
. l1

 

 

 

9-3 - :W’ --- " " -—- 12.5% -- untreated
A-6 - Mad. No. 517 ~-- " " --- 6.8% " -- treated
D-6 - " --- " " --- 19.3% " -- untreated
A-7 - L. trabea ---- " " --- 9.7% " -- treated
D-7 - l ---- " " --— 22.6% " -- untreated
A-S — P. incrassata - 56 " --- h.5% -- treated
D—S - " - " " --- 2.0% " -- untreated
A-9 - p; lepideus -- 270 " --- 1.9% " -- treated
D—9 - i“ -- " " --- 8.9% " -- untreated
1-11- P.1ncrassata - 280 " --- 25.1% " -- treated
D-ll- fl: _— " " --- 39.1% " -- untreated
A-l2-L. trabea ---- " " --- 23.2% " -- treated
D-12- " ~--- " " --- 27.M% " -— untreated
1e13- L. lepideus --— fl " --- 2.1% n -- treated
D-13- 1' " " --- 12.2% " -- untreated
A-lu- Had. No. 517 -- " " --- 5.2% " -- treated
D-lh- " -- " " --- 10.h§ " -- untreated
A~15- r. serialis -- " " --- -o.1%* " -- treated
D-15- " -- " " --- 6.6% " -- untreated
B-u - L. trabea -- 156 " --- 10.5% " -- treated
D-2l- " “ " —-- 1M.5% “ -- untreated

‘Negative values indicate slight gains.
Average loss in percent of oven-dry weight for treated wood - 8.H%

Average loss in percent of oven-dry weight for untreated wood - 16.0%
There is shown a striking uniformity of greater loss in the untreated
wood. Visual inspection bore out the factual evidence: the visibly
treated zones in the A.and 3 series definitely resisted the action of
wood-destroying fungi, while the central, untreated portions of the same
pieces appear to be as badly attacked as the matched untreated white fir.
But even more striking is the following compilation, since it

eliminates one variable by comparing parts of the same pieces of wood:

A-22

A-Zh

A-26

A-31

A-3u

B-ll

3-2u

3-27

3-28

0-3
6-16
0-25

I

0-27

 

 

 

 

 

 

 

 

 

- T.serialis ----(
- C. stercoreus -~-(
- Mad. No. 517 -—--(
- L. trabea ------- (
- C. stercoreus --—(
- Had. No. 517 ----(
- Had. No. 517 ----(
- C. stercoreus ---(
- C. stercoreus ---(
- T. serialis ----- (
- L. trabea ------- (
- L. trabea ------- (
- Mad. No. 517 ----(
- L. trabea ------- (
- C. stercoreus ---(
- T. serialis ----- (
- T. serialis ----- (
— Had. No. 517 ----(

‘Hegative values indicate

center
outside

center
outside

center
outside

center
outside

center
outside

center
outside

center
outside

center
outside

center
outside

center
outside

center
outside

center
outside

center
outside

center
outside

center
outside

center
outside

center
outside

center
outside

3.

O H
42'\
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slight gains.

p loss

83 days

1M5

159

90

132

132

105

90

107

90

II

II

II

87

 

deadlinfip.

In this compilation the average loss of oven-dry weight averaged
over 7.7% for the uncolored central portions, and less than 0.5% for the
outer, treated portions. The difference was consistent throughout the
tests, showing, furthermore, that the treated zones were highly resis-
tant to wood-rot fungi if the COpper-meta-arsenite were sufficiently
concentrated to color the wood.

Noteworthy was the variation in moisture content between specimens
used in each series to determine the average. The variation may well
account for some of the discrepancies in computed losses in oven-dry
weights. Series A.and C averaged 7.75% M.C.. series D averaged 7.76%
and series B averaged 7.78%. The twenty-one test specimens ranged from
7.69% to 7.83% M.C., being distributed rather equally about the general
averages. Taking the extreme possibility of a true 7.69% M.C. in a
3,500 gram specimen: if the averaged used as a base were taken at 7.78%,
then the error due to the use of the average would equal'almost 0.1% or
.003 grams.

It is entirely possible, however, that an error as large or larger
might enter because of physical changes if sterilization were accomp-
lished by the oven method, affording true oven-dry weights as a basis.
If any of the preservative were volatile, oven drying before testing
would be especially inadvisable,

The stain tests were not so conclusive as the decay resistance
tests, although the visual evidence most certainly pointed to a definite
stain resistance on the part of treated portions of white fir.

It is difficult to judge the degree of staining on pieces of wood
in a flask, particularly when tests were carried on over a period of two

years as this test was, but the results are presented as they were noted:

A-2
D-2

1.24
11.1;

A-5
9-5

A—16
D-l6

A-17
D-17

3-5
D-22

0-18

0-26

with

STAIN TESTS ON

rigidum

 

II

pilifera

 

I!

pluriannulata-

 

I
C

TI

nluriannulata—

 

pilifera

 

II

. pilifer

 

- G.

T

rigidum

 

IT

 

- Penicillium
i_1r_

sp.

- Aspergillus so. -

 

- C. pluriannulata-

 

‘6'.

T

rigidum
I

- I

- Chaetomium sp.

 

 

- C. pluriannulata-

 

- Mucor s9.

- C. pluriannulata—

More work is desirable

as many stain producing

270 days -

56 days -
II

56 days -
II

M6 days -

#6 days -
II

55 days -
II _

55 days -
I

90 days -
n _

90 days -
u _

36 days -
u _

30 days -
II _

“5 days —
- days -
days -

days -

days -

on the

C OPPER-tETA-ARSEI‘YI TE

treated
untreated

treated
untreated

treated
untreated

treated
untreated

treated
untreated

treated
untreated

treated
untreated

treated
untreated

treated
untreated

treated
untreated

treated
untreated

treated

treated

treated

treated

treated

89

badly spotted in center
stained over all surface

lightly stained in center
lightly stained all over

badly stained
heavily stained, one end

stained in center
spotted irregularly

unaffected
unaffected

few spots in center
spotted all over

spotted in center
lightly stained all over

molded all over
heavily molded

molded in center
heavily molded

center badly stained
badly stained all over

center lightly stained
lightly stained

center molded

spotted in center
stained light1y

molded heavily in center

lightly stained in center

subject of stain resistance alone,

fungi as are available.

COIICLTYS ION S

 

so

CONCLUSIONS

The writer does not intend to present this thesis as conclusive and
definite proof of the facts which seem to be borne out by the data collect-
ed in the experiment. Rather, the spirit is one of pointing out anparent

trends which the meager data seem to indicate:

1. COpper-meta-arsenite is a generally effective preservative in the
zone where its penetration is so concentrated that it is clearly visible
to the naked eye.

2. Other factors may inhibit wood decay to as great an extent as
c0pper-meta-arsenite or any other preservative. These factors include:
excessive moisture, insufficient moisture, and either high or low temp-
eratures. The data gathered in this exneriment have no bearing on
these actual points, but specimens of preserved wood seen in the field
have borne out the facts. Temperature and moisture deficiencies and
excesses must be continuous, however, to be effective.

3. Some mold fung will grow on the surface of copper-meta-ar-
senite treated wood, even when the concentration of preservative in the
wood is sufficient to protect it from decay fungi.

M. The fungus, Poria incrasseta, attacks even cepper-meta—arsenite

 

treated wood under favorable conditions, except where the salt concentra—
tion is very high.

5. Lumber or other timber products should be thoroughly air dried
before treating with copper-meta-arsenite in order that the salt concen-
tration may be high in the central portion.

6. It is recommended that no surfacing be done on cepper-meta-
arsenite treated lumber after the treatment, except possibly a very

‘

light planing to smooth raised erein. Surfacing removes the most decay-

Q

7.].

resistant part of the lumber. The nubli: should be taught to demand
heavily treated lumber, showing as much color as possible.

7. Decav resistance of treated or untreated lumber can be pre-
‘icted by laboratory tests with about a much relative accuracy as that
of commercial moisture-content indicators in the hands of untrained
users (2)(12)(32)(66)(113)(1tu)(1u6).

8. It is hirhlv desirable that further study be made on cepper-
meta-arsenite to determine its fire retardant Qualities; its quanti-
tative solubility; its possible danger to health through the release
of poisonous gases when attacked by certain mold fungi or fire (56)(15h);

and its effect on rodents which gnaw wood.

LI TERA'ITIIRE C ITE-m

92

PREFACE TO LITERATURE CITFD

The following list of citations is presented with the knowledge
that it does no more than touch upon the available literature covering

the field of wood preservation.

Citations included herein represent only a small part of pertinent
pdblicetions in the English language, and none but a very few translated
examples of the excellent material available in the German, French,_
Swedish and Russian languages. The sole basis for selection and in-
clusion herein was that the articles and books must have been examined.
and have been of some value in the preparation of this graduate thesis.
In only exceptional instances has the above objective been disregarded:
when a few citations from very old writers were lifted bodily from the_
bibliographies to guide future researchers to vsluab1e source material.
In all such cases, full acknowledgment has been accorded to the writer

whose bibliography furnished the unavailable reference.

Although the candidate is enrolled in the Department of Forestry,
in which'branch the library is not well stocked, this thesis is centered
on a branch of botany and of chemistry in which the library resources
are unusually rich._ In addition, various personal collection have
been made available, including the libraries of Dean Ernst A. Bessey
and Professors Forrest Ce Strong, Alexis J. Panshin and Paul A. Herbert.
The combination of the main library resources with the private libraries
mentioned has resulted in a very good foundation of source material,
particularly since a large portion of the list of citations lies within

the field of applied mycology.

 

‘ 1141!.I I

LITE? TY?“ CITED

1. Albion, Robert G. Forests and Sea Power. Cambridge: Harvard Univ.
Press. 1926.

2. Allen. 8.1. and C.H. Teasdale. Apparent relation between rainfall
and durability of zinc-treated cross ties. Amer. Wood Pres.
Assn. Proc. 15: 222-229, 1919.

3. American Creosoting Co. ioneer Work in Modern Wood Preservation:
Bethell, Boulton, Chanute. 1929.

M, American Wood Preservers' Association. Annual Proceedings. Wash.

1905 to 1938.

5. -------- . Wood Preserving News. monthly publication. Chicago.

6. -------- . Manual of Recommended Practice of the American Wood
Preservers' Association. Loose Leaf, currently revised.
Chicago.

7. Avenarius, R. Improvements in the treatment of tar oils for use as
wood preserving paints or coatings. (Abstract of original pat—
ent specifications). Eng. Pat. No. 7398, May 18. 1888. Jour.
Soc. Chem. Ind. 8: M03, May 31, 1889.

8. Bateman, Ernest. The Effect of Concentration on the Toxicity of
Chemicals to Living Organisms. U.S. Dept. Agr. Tech. Bull.

3H6. 1933.

9. -------- . Factors to be considered in testing of preservatives.
Amer. Wood Pres. Assn. Proc. 2M: 35-h2, 1928.

10. -------- . Remarks on eXperiments on toxicity of inorganic salts of
arsenic. Amer. Wood Pres. Assn. Proc. 2M: 7M, 1928.

ll. -------- , and R.H. Baechler. Some experiments on the toxicity of
inorganic salts (Part 7). Amer. Wood Pres. Assn. Proc. 23:
u1-u7, 1927.

 

Ills.

9M

12. Bateman, Ernest. Factors governing the Permanence of preservatives.
Amer. Wood Pres. Assn. Proc. 23: 87-92, 1927.

13. -------- . Coal-tar and Water-gas Tar Creosotes: Their Properties
and Methods of Testing. U.S. Dept. Agr. Bull. 1036. 1922.

1M, -------- . Visual Method for Determining the Penetration of Inorgan-
ic Salts in Treated Wood. U.S. Dept. Agr. For. Serv. Ciro.
190. 1911.

15. Bessey, Ernst A. A Textbook of Mycology. Phila.: Blakiston. 1935.

16. Bethell, John. Patent for preserving timber, rendering wood, cork
and other articles more durable, etc. Patent No. 7731, July
1838. (From Citation No. 3).

17. Blake, E.G. The seasoning and Preservation of Timber. N.Y.: Van-
Nostrand. 1925.

18. Boulton, Sir Harold. A Century of Wood Preserving. London: Allan.
1930.

19. Boultcn, Samuel B. The antiseptic treatment of timber. Proc.
Inst. Civ. Eng. 78: l2-7H, 188M.

20. Boyce, John Shaw. Forest Pathology. N.Y.: McGraw-Hill. 1938.

21. -------- . A Study of Decay in Douglas Fir in the Pacific North-
west. U.S. Dept. Agr. Bull. 1163. 1923.

22. -------- . Decay in Pacific Northwest Conifers. Yale'Univ. Osborne
Bot. Lab. Bul. 1. 1930.

23. -------- . Decays and Discolorations in Airplane Woods. U.S. Dept.
Agr. Bull. 1128. 1923.

2U. Burnett, Sir William. Patent for preserving timber, No. 77h7, July
1838. Idem. No. su37. March, 1839. (From 3.3. Boulton).

 

i.\.

 

27.

28.

310

320

33.

3h.

35.

36.

95

Burt, H.P. On the nature and properties of timber. Minutes of
Proc. Inst. C.E. 12: 206, 1853.

Card, James P. Preserving wood. (Abstract from original patent _
specifications). U.S. Pat. No. 25u27u, Feb. 28, 1882. Jour.
Soc. Chem. Ind. l: 151, April, 1882.

Cato Censorius. De Re Rustica. 18. (From 5.3. Boulton).

Chapman, A. Dale. Effect of steam sterilization on susceptibility
of wood to bluestaining and wood-destroying fungi. Jour. Agr.

Res. M7 (6): 369-37“, Sept. 15. 1933.

Chapman, William. Treatise on the Preservation of Timber. London.
1817.

Chemonite Wood Preserving Co. Chemonite and the Control of Wood
Destroying Agencies. San Francisco: Sunset. 1937.

Chidester, Mae S. Further studies on temperatures necessary to
kill fungi on wood. (Advance report). Amer. Wood Pres. Assn.
Proc. 1939.

Colley, Reginald H. and C.T. Rumbold. Relation between moisture
content of the wood and blue stain in Loblolly pine. Jour.
Aer. Res. h1(5): 389-399. Sept. 1. 1930.

-------- . The Prevention of Decay of Wood in Buildings. U.S.Dept.
Agr. For. Prod. Lab. Mimeo. 82. Jan. 9, 1928.

-------- . Rotten wood. Timberman 25: 56-57, May, 192‘; also in
So. Lumberman 11h: us-ug, May 17, 192k.

Cross, G. J. Impregnating and preserving soft wood and timber.
(Abstract of original patent specifications). Eng. Pat. No.
2957, 1882. Jour. Soc. Chem. Ind. 2: 179, Apr. 29, 1883.

Cummings, J.E. Some modern aspects of wood preservation. Proc.
Soc. Chem. Ind.. Vict. 37(5-3): 1295-1296. 1937.

37.

38.

39.

Ml.

1+2.

Ll3.

mu.

“5.

MS.

”7.

MS.

\0
O\

Curtin, L.P. and others. Experiments in wood preservation, Part 2.
Arsenites of copper and zinc. Ind. & Eng. Chem. 19: 993-999,
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...... -. Edition in, 1937.
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r I via 1 .Einililv

. »

 

98

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WI]

50' ---

v'

81. --.

82-

\JD

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79. -------- . Decay of lumber and building timber due to Poria incras-
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a:

“A". .r -

' 10":IMnJm“u‘-JL—‘n .

86. Hunt,

100

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89. -------- . Factors that Influence the Decay of Untreated Wood in

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101

Kofoid. C.A. and others. Termites and Termite Control. Berkeley:
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105. -------- . An improved process and apparatus for treating wood,

...J

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113.

118.

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‘ I
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v in

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123.

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H
R)
0’»)
O

130.

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n
M(h): 165-

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10k
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-..-g“ 1. M-oo

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105

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rd; y‘._:VIV"-a‘-l'£ . ‘ " .

106

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157. Trotter, H. AS-U

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159. -------- , and -------- . A new test for measuring the fire resist-
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160° Unger, Franz. Originare Bildung der Krankheitsorganismen. ISUO.
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161. U.S. Dept. Agr. Forest Service, Forest Products Laboratory. Test-
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162. -------- . List of Publications Relating to Fungus Defects in For-
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163. -------- . List of Publications on Wood Preservation. Mimeo.
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166. ------- . Weathering and decay. Tech. Note No. 221.

167. -------- . Cause and prevention of blue stain in wood. Tech.

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173.

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177.

178.

107

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Von Schrenk, Hermann. Decay of Timber and Methods of Preventing
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Wogener, W.W. Lentinus lenideus, Fr.: A cause of hear

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