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I .rIW.‘ of-uil ‘r\ THESIS This is to certify that the thesis entitled way of the Effect of Fire—Retardant 1 :tments of Six Hardwood Speciea. presented by Everett Lincoln 31113 has been accepted towards fulfihnent of the requirements for ‘0 m. SI degree hi Forestgx /‘ / . / ll . ’h / , \ W T r) k MaJor {professor Date November :9. 194; \\ A S’l‘UL‘Y 0F Trix; EFFECT OF FIRE-RETARDANT 'ITiEA'lTSELTS OF SIX lu'mM’J'UCD SthIES by EVERETT LINCOLN ELLIS m A THESIS Submitted to the Graduate School of Michigan State College of Agriculture and Applied Science in partial fulfilment of the requirements for the degree of MASTER OF SCIENCE IN KDRESTRY Department of Forestry 1945 A. B. D. A. B. C. D. I. II. 1H TABLE OF CONTENTS HISTORICAL BACKGROUND GERERAILEQESEPERATIOKS \ . . .. ...,...---M ...—...— COMBUSTION OF WOOD EFFECTIVENESS OF CHEMICAL FIRE-RETARDANTS MEASUREMENTS OF FIRE-RETARDANT QUALITIES OF WOOD EFFECT OF VARIOUS ROOD CHARACTERISTICS ON TREATMENT HE PROBLEM SELECTION AND PREPARATION OF MATERIAL FOR TREATING TRLATDRNT 1. PROCEDURE 2. DISCUSSION OF TREATING DATA PREPARATION OF TREATED NATRRIAL FOR TESTING TESTING I. PROCEDURE 2.. DISCUSSION OF RESULTS 3. ANALISIS OF VARIANCE AND COVRRIANCR STORIRuRTTRTR RRTSTRDRR APPENDIX DISTRIBUTION OF CHEMICALS IN TREATED MATERIAL MOISTURE GRADIENTS IN TREATED MATERIAL ISSODS ACKNOhLEDGEEHT Grateful acknowledgment is hereby extended to the following men without whose assistance the solution of these problems would have been impossible. To Professor A. J. Panshin for his constant advice and supervision of all my work special gratitude is due. Sincere thanks to Mr. F. W. Gottschalk and the American Lumber and Treating Company of Chicago are extended for their contribution of material and apparatus and for their cooperation in these problems. To Messrs. G. M. Hunt and G. C. McNaughton of the United States For- est Products Laboratory acknowledgment is due for their assistance in answering certain technical questions. A debt of gratitude is owed to Professor E. Leininger for his direction and guidance in the chemical analysis work; and to Professor W. D. Baten sincere thanks are given for his assistance in the preparation of the Analysis of variance and Covariance. A STUDY OF THE EFFECTS OF FIRE-RETARDANT TREATIEI‘ITS OF SIX IIARD‘HOOD SPECIES vi INTRODUCTION This report deals with the data derived from investigation of the fire-retardant qualities-1 of six hardwood Species treated (I) with various retentions of a mixture of chemicals consisting of 60% ammonium.sulphate, (NH4)ESO4; 20% boric acid, 33B033 10% diammonium phosphate (NH4)2HP04; and 10% borax, NazB4O7, and (2) with the same mixture of chemicals to which a water-soluble wood preservative (Wolman Salts Tanalith) was edded.2 Six species of hardwood lumber were used in this study, namely: Red oak, Quercus borealis Michx. - from central Tennessee Yellow poplar, IRFERREERIBEnIBEEPIIEPfiflk‘ - from southern Missis- sippi White oak, Quercus alba L. - from central Tennessee Birch, Betula sp. Michx. - from northern Michigan maple, Ace: saccharum harsh. - from northeastern Wisconsin Red gum, Liguidambar styrgeiflug E“ - from central Louisiana l. Fire-rztardant treatment is a better term.thEE:TITEEFSOTIEEHWEICRMR is a misnomer because wood cannot be rendered impervious to fire. 2. welman Salts Tanalith is a commercial wood preservative consisting of sodium.chromate, dinitrophenol, sodium fluoride, and disodium arsenate. - \J EISTOR‘ICAL _I_3:A.CKGRCUND Wood has been used for construction since the earliest times. It was recognized centuries ago that wood which was rendered fire- retardant would be enhanced in value for building. In the days of Emperor Augustus the Romans used a mixture of vinegar and clay to form a fire-retardant coating for their buildings (28;Kflfl5.3 Today the inflammable nature of wood still remains one of the chief limp itations in the use of wood construction. In the United States the advent of commercial "fireproofing" came in the "nineties" with the first patent covering the use of ammonium.phosphate and ammonium sulfate granted in 1893 CLEED. The first commercial "fireproofing" company was organized soon after to fulfill demands created by the United States Navy and the New York City Building Department. Although wood treated by early fire-retar- dant processes was effective in reducing fire hazard,4)it had several objectionable properties which led to its discontinuance by the Navy. The corrosive nature as well as the hygroscopic quality of the chem- icals used caused serious trouble when the treated material was used in damp situations. Hewever, when used in interior construction, fire-retardant wood has proven lasting and effective (HF). No statistics are available showing how much wood is being treated'with fire-retardant chemicals at the present time. The imp petus of government regulations for the use of fire-retardant wood in certain types of structures such as ordnance plants, aircraft hangars, and locks has led to a great increase in the quantity of treated 3. Nfiiibrs in parentheses indicatSHCItEtIOEs Idseed at the end Of this report. ‘ 4. According to Hunt and Garrattr(l7)a.successfully "fireproofed" wood is one that will not contribute to its own combustion and will not further the spread of flame, i.e., will not burn or glOW'when the source of heat is removed. lnterial produced. Pressure impregnation is the only method used commercially today to "fireproof" wood. Surface coatings are successful to a certain extent, but they lack permanence and cannot give as full protection as thoroughly impregnated material, since, once the protective coating is destroyed or broken, the wood exposed will burn the same as untreated wood (17,8, 25.26). Structures can also be rendered more fire-resistant by utili- zation of proper design. The so-called "slow burning heavy timber construction” which utilizes large size timbers is quite successful in preventing failure of wooden members when exposed to fire (11.1,; 8,. .29). The use of sprinklers and fire-steps also leads to greater fire safety (19.). At the present time fire-retardant wood is becoming more impor- tant than ever before. Due to the shortage of metals, wood is being used for many purposes formerly filled by metals. The use of wood for construction is greater than it has been for years. If fire-re- tardant wood is made available, many more substitutions for metal may be realized. The appalling losses from fire in.wooden warehouses could be drastically curtailed had fire-retardant wood been used in their construction. One of the chief dangers from fire is the inflammable nature of the contents of a building. This cannot be avoided, but the destruction of the building can be prevented. Such protection would obviate the necessity of rebuilding even though the contents of the building were destroyed by fire. The future of fire-retardant wood is very promising. As speci- fications for fire-retardant wood become standardized and fire-re- tardant wood is made generally available, it should become and remain a major construction.material for many types qf building. When insur- ance companies recognize the value of fire-retardant wood and lower their premiums further impetus will be given to the use of fire-re- tardant wood. At the same time, as the effectiveness of fire-retardant wood is proven in service it will become more in demand by wood-using industries and thus become more generally available. Hewever, many problems remain yet to be solved in reference to leaching of chemicals, decay resistance, gluing and finishing preperties of fire-retardant wood. GENERAL CONS IDRRATI CE COMBUSTION 0F WOOD According to Hewley and Wise (1Q wood begins to decompose when heated to about 270° 0. Prince (20) found that wood would ignite when heated for a sufficient period of time between 180° and 200° C. When wood is heated first the moisture in the wood is driven off and then various volatile extractives are liberated. Upon reaching de- composition temperatures combustible gases are liberated and are ignited leaving a residue of charcoal. Continued heating of the charcoal causes it to ignite, but at a higher temperature than wood ignites and burn to carbon dioxide and watgr vapor. The combustion of wood is exothermic and produces considerable heat (6000 to 8000 Btu ppr pound of wood). The combustion of charcoal at a higher temperature also produces heat but requires more heat to ignite. Under proper conditions wood may even ignite spontaneously, a common phenomenon of sawdust and pulp piles. The temperature at which wood ignites depends upon many factors such as moisture content, density, porosity, available air, size of the piece, and time of exposure (23). EFFECTIVENESS OF CHEMICAL FIRE-RETARDANTS As far as has been determined no chemical wholly prevents com- bustion and charring of wood (28). Several investigators have found that wood treated with fire-retardant chemicals has an increased ig- nition temperature, i.e., it will require a higher temperature to ignite the treated than the untreated wood. The magnitude of this increase which.may be as much as 200° C. above the ignition temper- ature of untreated wood depending on the chemical used. A number of theories have been proposed to explain the exact effect of these chemicals upon the combustion of wood (1123,29). Since the purpose of this paper is not to discuss the sources of effectiveness, but to measure them, one theory will be discussed. According to this theory the presence of chemical in someway causes a rapid formation of hard charcoal which increases the ignition temperature and absorbs con— siderable heat (unease). The writer's personal opinion after watching some 1,000 tests is that this theory is the most likely of those so far offered. MEASUREMENTS 0F FIRE-RETARDANT QUALITIbS 0F WOOD The first method used to determine the fire-retardant qualities of wood was suggested by two Dutch professors in 1887 and almost as many tests have been suggested since that time as there have been investigators. Hartman ((15) gives a brief historical sketch of the great number of tests that have been designed. In general, tests of fire-retardant wood are made on small-sized material and measure one or more of the following properties: flame spread, flame pene- tration, duration of flaming, and duration of glowing «11,23}£;5”. 1156.335); . In this country there are four standard tests in common use: the fire-tube test, the crib test, the special crib test, and the timber test (23,6, 3). The oldest of these are probably the New York City "Timber Test" and "Crib Test". Briefly the timber test, a flame-penetration test, consists of exposing two matched pieces of treated wood to a crucible furnace Opening at a temperature of 925il4° C. for two minutes. Observations are made upon the duration of flame and glow after flaming has ceased. The depth of flame penetration and a percentage reduction of wood area are measured, and weight loss of the piece in per cent is computed ((6,3).X The "Crib Test", as develOped by the New York City Building Code (m333 consists essentially of burning twelve pieces, one-half inch square and six inches long, under controlled conditions. The pieces are arranged in a crib of three rows of four pieces to the row and exposed to a flame from.3/B inch Tirrill burner having a maximum tem- perature of 925i14° 0., measured by an lS-gage chromel-alumel ther- mocouple. The flame is applied for two minutes and observations are made of the following: aduration of glow after flaming, maximum.height of flame, duration of flaming, and weight loss. This test is a flame spread test. The "special" Crib Test was developed by Prof. W.J. Irefeld of Columbia University and is a modification of the NeW'York Crib Test (:2 ,, 653:. Both crib tests require a controlled rate of exhaust in the fume hood. The ”special" Crib Test uses a double cantilever spring scale to register weight loss in per cent, a permanent wire frame for holding the specimens, and a movable shield which surrounds the specimens during the test. A.Meker burner with a flame temperature of 982£l4° 0.. measured with an lB-gage chromel-alumel thermocouple is placed beneath the crib of twenty-four pieces for three minutes, each piece measuring one-half inch square by three inches long. 0b- servations are made at half minute intervals of temperature and loss in weight, the maximum.temperature and time when it occurred, less in '-6- weight when blazing ceased and time of occurrence, and the duration or SIWe The "fire-tube" test will be described in detail further on in this paper.5 many other tests have been devised as has been pointed out (pg. 5). These miscellaneous tests include tests of full-size assemblies, various flame spread tests, and others. . The various tests in.use are not directly comparable and do not measure the same fire-retardant qualities. This in the past has resulted in confused specifications for performance of treated material and has undoubtedly delayed the more extensive use of fire-retardant 'wood. Further information on.various fire-retardant tests can be found in the publications listed in the footnote.5 EFFECT OF VARIOUS WOOD CHARACTERISTICS ON TREATMENT When several species of wood are subjected to the sums pressure impregnation treatment the results vary for the different species. These differences are due at least in part to the differences in structure of these woods. In this study, six species of hardwoods with highly divergent physical properties were used. Red and white oak, gpercus borealis-Michx. and gpercus alba-L., belong to the ring- porous group of woods, that is, their wood is characterized by large springdwood pores (vessels) and comparitively smaller summerdwocd pores. White oak differs from.red oak in one important respect that the Springdwood pores in the heartwood of white oak are generally more or less filled with tyloses, small balloon-like structures that quite effectively plug these vessels and restrict the passage of liquid e.‘ 5. A.more complete description of the four tests described can be found in the 1941 Proceedings of the American Society for Testing Materials (if), and in the 1942 Proceedings of the American Wood Pre server's Association {(6’)} through them. The scarcity of tyloses in red oak heartwood largely accounts for the fact that it is much.more easily treated than heart- wood of white oak. Both species of oaks are of about the same density, although white oak is usually slightly more dense. The four remaining species, namely: yellow poplar, Bipiodgndron ”..-- yhrsh., and red gum, qupidambar_stypagiflgapl23 are diffuse-porous woods. This means there is little difference in size of spring and summerdwood pores.(vessels). Of the six Species, red gum.is the most difficult to treat. This fact is probably due to its thickdwalled fibers, small intervessel pits, and perhaps also to heavy infiltrations in the heartwood. In addition to structural variations of different species, differ- ences in treating results may also be traced to sapwood and heartwood. Sapweod differs from.heartwood chiefly in that it was still functioning as a living part of the tree when the tree was cut into lumber. The . physiological changes involved in the transformation of sapwood to heartwood are not fully understood, but it is known that heartwood consists of dead tissue and is usually modified by infiltration of various organic substances, which generally make heartwood darker in color, heavier, and more impervious to the passage of liquids than sapwood. Red gum sapwood is white or pinkish, while its heartwood is reddish- brown. As was pointed out in one of the preceeding paragraphs red gum heartwood is very difficult to treat, while its sapwood treats easily. Sapwood and heartwood cells are of the same size, so the presence of infiltrated substances and gum.deposits in the heartwood of red gum must account for the greater difficulty in treating heartwood of this species. In varying degrees a similar effect in treating is obtained in the case of sapwood of other Species. The effect of density upon the treating characteristics of various woods is also quite pronounced. More dense Species are more difficult to treat because there is less available air space in these woods. Since more dense woods have a greater weight per volume than lighter woods, hence, more wood sub- stance per volume, it is to be expected that there would be less available space in heavier woods to be filled with solution during treatment.6 SELECTION AND PREPARATION OF MATLKIAL FOR TRmATING The wood of the six species used in this study was treated to give five retentions of one to six pounds of dry chemical per cubic foot of wood. Each treatment was duplicated. A second series of treatments were also made similar to the first with the exception that a water- soluble wood preservative, welman Salts Tanalith, was added to the fire-retardant solution. These treatments will be described hereafter as Series I and Series II respectively. First grade of nominal one inch thick stock of each species was supplied in quantities of approxi- mately one hundred-twenty lineal feet each by the American Lumber and Treating Company of Chicago, Illinois. No selection of material on the basis of specific gravity or sapwood and heartwood was possible. The values for specific gravity and sapwood percentages are given in Table 1. All the material received was dried to a uniform moisture content of approximately seven per cent7 in the college dry kiln. When some 3: Further information on‘the'structure and preperties of thejwood§"'r‘ considered in this problem my be found in citation ‘9, at the end of this report. 7. Based on weight loss when oven-dried and oven-dry weight of wood. -9- pletely dried all the lumber was surfaced to seven and oneAhalf inches width and three-quarters of an inch thickness. The surfaced boards were then cut into four foot lengths and replaced in the kiln, where they were subjected to a conditioning period allowing them.to redry to the desired moisture content (seven per cent). Each piece was then stamped with the preper letter and number designation using steel dies. The identifying symbol consisted of three parts. The first number indicated the poundage retention of dry salt desired, the letter following identified the species and the last number indicated whether the board was in the first charge of the desired retention or in the second charge. The following letters were used to indicate the Species considered: 0 for red oak, Y for yellow peplar, W for white oak, B for birch, M for maple, and G for red gum. A letter W following the treat- ment number and proceeding the species letter indicated the Second series of treatments in which Wolman‘Salts was added to the fire-retar- dant solution. The letter U indicated an untreated control board. For example, 6W2 indicated the following: the board received a treat- ment designed to leave six pounds of chemical per cubic foot of wood; the board was white oak; and it was the second board to be so treated. In as far as possible an untreated board, a board selected to receive a three pound and a six pound retention of dry chemical per cubic foot of wood were chosen from the same piece of lumber. TREATMENT l. PROCEDURE. All of the wood was treated in one of the two experimental retorts in the forestry department preservation plant. This retort measured one foot in diameter by four feet in length and was arranged with automatic control of temperature and pressure. Be- fore using the apparatus the Bristol control instruments were cali- -10- brated and adjusted as carefully as possible. A treating solution of 2.8 per cent concentration of salts by weight should give a retention of approximately one pound of dry chemi- cal per cubic foot of wood with most woods. The first treating charge was used as a check for this assumption. The solution concentrations were varied to attempt to give retentions of one, two, three, four, five, and six pounds of chemical per cubic foot of wood. The treating solution in the first series consisted of sixty per cent ammonium.sul- fate, (NH4)2SO4, twenty per cent boric acid, H3803, ten per cent borax, Na28407, and ten per cent diammonium.phosphate, @H4)2HPO4, to which solution two per cent by weight of potassium dichromate, K20r207, was added as a corrosion inhibitors. The second series consisted of the same solution as described to which 0.93 per cent ‘Wolman Salts Tanalith (a wood preservative consisting essentially of sodium chromate, dflnfltro- phenol, sodium fluoride, and sodium arsenate) by weight was added and from which potassium.dichromate was eliminated. Concentrations of chemicals by weight ranged from 2.8 to 16.8 per cent for one and six pounds dry salt retention respectively. The solutions were prepared by weighing out the chemicals in the desired amounts and dissolving them in a container of hot water. Then this solution.was diluted to the desired concentration by adding water in the working tank which is a closed tank on a weighing platform. About two hundred-fifty pounds of solution were prepared for each charge and additional chemicals were weighed out and added to the solution remaining after the previous treatment, to bring its concentration and amount to the proper point for the next charge. Each charge consisted of six boards, one each of the Species used. 8. Although the-treating solution was almost neutral withoutmthemaddition of the potassium.dichromate, it was added to insure protection against corrosion. -11- The boards were weighed to the nearest hundredth gram and all di— mensions measured to the nearest one-sixteenth inch before treatment. In addition, moisture contents were determined by using an electric moisture meter. The boards of each charge were then placed in the retort, separated by stickers, and arranged to prevent floating. After the retort was sealed an initial vacuum of from 29;; to 29 3/4 inches was drawn and held for approximately half an hour. Then without releasing the vacuum the treating solution, preheated to a temperature of 125° F., was introduced. Pressure was then applied at 175 pounds per square inch for a period of twelve hours. This period was thought to be sufficient to give refusal penetration9 in all species and was based on the results of the first charge when a longer time was allowed. Commercial treatment now demands treating periods as long as thirty-six hours to attain the desired retention in species such as Douglas fir, so it is probable that refusal penetration was not achieved in much of the material. However, all of the charges re- ceived similar treatment and hence are quite directly comparable. The pressure was released at the end of twelve hours and the un- used treating solution was all returned to the working tank. Then a period of a half hour was given to allow for "kickback"10 of treating solution from the charge. After this period the retort was cpened and the charge removed. Each board was immediately reweighed and re- measured before being placed on stickers in a close pile for storage before redrying. §:“"REfusal penetrationfisnthe‘absorption of solution to complete" saturation of the wood, i.e., until all available air spaces in the wood are filled with solution. This ordinarily requires at least forty pounds, or more, of solution per cubic foot of wood. 10. "Kickback" is the amount of solution expelled by the‘Iood after the pressure has been released. It is due to the internal pressures in the‘wood'doweIOPed‘durinngrossure treatment and is common to all preser- vative treatments. Retentions were calculated from the absorption of solution of that particular concentration and based upon the volume of the board when removed from the treating retort. In general, the treatment had no deleterious effect upon the boards, however, one or two boards did show slight warping and cupping. The color of the treated boards was little changed except in the second series where a slight yellowing was noticeable. It was also noted that the presence of a relatively large amount of chemical had a serious dulling effect upon the saws used to cut the treated material into test specimens. 2. DISCUSSION OF TREATING DATA. Tables 1 to 6 include the es- sential treating data of all the material used in these experiments. It can be readily seen by reference to these tables that several factors influenced the retention of chemical by each board. Chief among these factors is probably the amount of sapwood present. Boards 'which contained sapwood are naturally more easily penetrated and hence retained more chemical (see pages 7 and 8). Table 6 shows that red gum.is very difficult to treat since the highest retention obtained was only slightly over three pounds of chemical per cubic foot of wood. Had the treating period been pro- longed undoubtedly more chemical could have been forced into red gum and in some cases into red and white oak. As was previously mentioned (pg.11) present-day commercial Operation often subjects charges to pressure periods of two or more days to achieve refusal penetration (absorption). To determine the effect of a longer treating period on red gum, piece 4G1 was returned to the treating cylinder after the usual twelve hours pressure and given an additional twelve hours of treatment. This increased the retention from 0.77 to 1.13 pounds of dry salt. It seems evident then that the concentrations used to give -13- retentions from one to six pounds of chemical per cubic foot with the other species treated will not give similar retentions of dry salt in red gum despite the length of time pressure is maintained in the treating cylinder. White oak was found to be little more difficult to treat success- fully than red oak. A few boards were notable exceptions to this statement as can be seen in Table 5, boards 5hl, 4WW1, and 4WW2. Visual examination of these boards failed to disclose any reason for this discrepancy; it is felt that the reason for this behavior is in some way connected with the minute anatomy of the boards in question. Yellow pOplar was the most easily treated wood followed in order by birch, maple, red oak, white oak, and red gum. Since it is very difficult to distinguish maple sapwood from heartwood, the effect of sapwood in maple cannot be evaluated. It is notable, however, that the two most easily treated species were those in which the boards treated contained the greatest amount of sapwood. The moisture content of the boards treated was very homogeneous. It is interesting to note that those boards in which the absorption of treating solution approached a condition of refusal, namely, about forty pounds of solution per cubic foot of wood, retained approxi- mately the desired amount of dry chemical. This again points to the fact that the treating times were probably insufficient for species such as red and white oak to give refusal absorptions. In the second series of treatments in.which Holman SalusTanalith was added to the fire-retardant solution, the concentration of Welman Salta(0.93% by'weight) was designed to give a dry salt retention of nolman Saltsof 0.30 pounds per cubic foot of wood. Tables 1 to 6 show that this ideal was achieved in most cases where the desired re- tention of chemical was obtained. However, since the components of the at) at 38 a1 P) nt 68 a1 +~ nt :al es 1 1 2 33.4w... 5566 18; nt es :al lg cm ant :es :al 55 LE mt 368 ml -20~ fire-retardant solution, especially borax and boric acid, are them- selves somewhat toxic toward fungi (17 , adequate decay protection is probably afforded in both series of treatments. The present Federal specification designates the first series as Type 2 treatment (12), which is acceptable for material used in government contracts as being both fire-retardant and decay-resistant. As was pOinted out on page ... 6, treatment of several species with such highly divergent prOperties as the six used in these experiments could scarcely be expected to be uniform. The different densities, permiabilities, amounts of sapwood, and structural characteristics of these species make their simultaneous treatment difficult. PREPARATION OF TRLATED MATLRIAL FOR ThSTING After treatments were completed for each series the boards were taken from the close pile and placed in the dry kiln. The wood was then dried with a mild kiln schedule to an equilibrium moisture content of approximately seven per cent.11 Tables 7 and 8 present the kiln schedules used to dry the treated material and the untreated control boards prior to cutting them.into specimens for testing. The dry bulb temperature was kept below 125° F. to prevent volatilization of chemicals, particularly ammonium salts, from the wood. The schedules were very mild also to prevent the'blooming"13 of salts on the surfaces of the boards and to prevent checking and warping during drying. As will be shown in Appendix I there is a marked concentration of chemical gradient in the dried material. This same result was shown by Moore (18). Decry (10) showed that the equilibrium.moisture content for a ll. EquIIiBFIEmffiBisthrb”Ehht6hETit"the moisture cassshwfwssa will reach when kept for a sufficient length of time at any controlled temperature and relative humidity. 12. The appearance of crystals on the surface of treated wood is known as blooming. “d2 1'- given relative humidity is slightly higher for treated wood than for untreated wood, hence the final drying stage was carried on at a temper- ature and relative humidity designed to give an equilibrium moisture content in untreated wood of about six per cent. Calculation of moisture contents were made on the basis of loss in weight when oven-dried. divided by the oven-dried weight of the sample. No deduction for retention of chemical was made in this calcu- lation which is the method in common usage by most investigators. When a deduction for chemical is made, however, a difference in moisture content of only one to three per cent was observed in control tests. Thus, for high retentions of chemicals moisture contents listed in the following tables of data will be higher than what might be termed "actual" moisture content by one to three per cent. Unfortunately the circulation in the dry kiln partially failed during conditioning13 of the last of Series I and the moisture content of some of the test material rose above the desired 7i3%. The failure was of such a nature as to be unnoticed until the results of check samples dried in the oven (at 100° C.) to oven-dry weight were avail- able.' The dry kiln fan.was repaired prior to conditioning the second series and no further trouble was experienced. As will be pointed out (pg. 27) the use of final weight loss as the criterion of effectiveness of fire-retardants in these tests minimizes the effect of slight discrepancies in moisture cpntent since final weight loss for the same material at different moisture contents was proven to be almost identical. Each board when dry was cut into the proper size for fire-tube testing as shown in Figure l for Series I and as shown in Figure 2 for Series II. Each fire-tube test specimen measured 46" x 3/8" x 3 4" M ..-. ...- -.- h..-- .—. ---' ...---oo— T3. see page '45:” -22.. TABLE 7 DRYING OF TREATED WOOD SERIES I-CHARGES 101 TO 602 INCLUSIVE DRY BULB TERP. hET BULB TEkP. RELATIVE HURILITY NUKBER DAYS E.E.C. CF ROOD* 120° F. 113° F. qu 4 13_4% 120° F. 108° F. 67% s 10.8; 120° F. ' 100° F. 49% 2% 7.9% 120° F. 92° F. 32;}; lfi. 6.13:; TOTAL 28% TABLE 8 SERIES II—CHARGss 1w01 to swoz INCLusrns DRY BULB TEHP. WET BULB TEMP. RELATIVE HUMIDITY NUKBER DAYS E.M.C. OF ROCE* 120° F. 113° F. 80% 3% 13.4% 125° F. 113° F. 64% 3 10.8% 125° F. 107° F. 52% 3% 8.5% 125° F. 101° F. 43% 6% 7.0% 120° F. 99° F. 33% 5 6.5% TOTAL 22% * Equilibrium moisture content of untreated wood at that temperature and relative humidity.‘ 2.2 3:- and all specimens from the same board were numbered as shown in Figures lsand 2. Each specimen was numbered as cut and all specimens from each board were marked and kept in separate bundles, which were stored in a dry place pending conditioning and testing. As was previously mentioned (pg.12) , the treated wood had a rather marked dulling effect on the saw. . Just prior to testing in the fire—tube, the specimens to be burned were separated from.their respective bundles and given a condi- tioning drying treatment in the kiln to guarantee preper moisture con- tent.' A temperature of from 120° to 125° F. and a relative humidity of approximately thirty per cent, a combination which gives an equilibrium moisture content of approximately six per cent in untreated wood, were used. This reconditioning treatment was for a period of two to three ' days. Since no constant humidity room was available this redrying treatment was resorted to in order to insure preper moisture content (723%). Thirty specimens were prepared for testing at one time. Upon re- moval from the dry kiln they were cut to forty inch lengths by remov- ing three inches from each end. The end of specimen no. 6 was used for the determination of moisture content. The use of common hooks (such as are commonly referred to as cup hooks) to support the speci- mens was found to be unsatisfactory with the harder, more dense species such as oak and maple, so a special small hook (Figure 4) was utilized. A small wire nail was driven through the test specimen one-fourth to one-eighth of an inch from.the end and the special hook was slipped over the protruding ends. This system of supporting the Specimens proved very satisfactory. T”°TING O 116031 I CUTTING DIAGRAM 1'08 FIRE-TUBE TEST SPECIMENS SERIES I I in 45" J ' '. o :7 (E: j: fi: fi: u c:-——-——— -— —— —— —— —- -1 . J 7’5. ‘2— ‘ a “ a FIGURE 2 0mm DIAGRAM TOR FIRE-TUBE TEST SPECS/3:3 SERIES II .1. if i 3 ' {we . ‘I‘ z: —— -— -— —-— -—:.27 a. -:=: ‘r__ —— —J: I u I k '10 ; nouns 3 BOOK TOR SUPPORTIXG l'IRE-T'JBE TEST SPNIMS l. PROCEDURE. The Forest Products Laboratory fire-tube test was used in these experiments to determine the fire-retardant qualities of the treated wood. This test is described in detail by Truax and - Harrison (23).15 Directions for the Operations and set up for this test are given in Mimeograph R900 of the United States Forest Products laboratory (3?). The apparatus16 consisted of a sheet metal tube counterbalanced in such a way that weight losses in per cent were recorded by a pointer moving across a scale as the specimen burned. A low-form Bunsen burner controlled by a manometer supplied the necessary heat for the test. Temperature was measured by a fourteen-gage chromel-alumel thermocouple using a Weston millivoltmeter and the prOper table for conversion of millivolts to degrees Centigrade. A hood over the apparatus alloued the gases and Humes to be drawn off by natural draft during the tests. The specimen.was placed in the tube suspended by a Special hook (Fig. 3) after the tube had been balanced empty and with the flame in place at 100 per cent weight loss on the chart. The flame which had previously been standardized to a length of eleven inches, with an in- distinct inner cone and a temperature of 8503250 6., gave a temperature at the tOp of the empty tube of approximately 185150 C. After the specimen‘was in place the flame was introduced into the tube and allowed to play against the side of the tube not touching the specimen until a temperature of 100° C. was indicated by the millivolt deflection. The purpose of this preheating was to give a constant starting temperature and thus equalize varying room.temperatunes. When the tube had reached a temperature of 100° C. the flame was placed one inch directly below the lower end of the pdece being tested 15. For a comparison of .this test to others see c’i'ftastitch..37'at“’thémendw of this report. 16. See Plate 1. PLATE 1 1 i i ~27- and the timing clock started. Readings of temperature and weight loss were made at half minute intervals and the time of maximum temperature, weight IOSS‘When blazing ceased, time when blazing ceased, and the 17 The flame was moved so as time when glowing ceased were recorded. to keep it directly beneath the specimen as it burned and it was allowed to remain beneath the Specimen for four minutes after which it was removed. After flaming ceased, readings of temperatures and weight losses were continued for two minutes or longer and then the tube was removed, emptied, rebalanced, and a new specimen placed in the tube. The Series I and the untreated material were all burned in a fire- tube furnished by the American Lumber and Treating Company. The Series II Specimens were burned in a tube built for the forestry department. There was some difference in the performance of the tubes, but very slight as will be shown in the analysis of variance and covariance made on the material tested in the two tubes. The tubes were constantly adjusted to insure proper balance and Operation. Six specimens from each board were burned and the data on the last five were averaged to give values indicative of the whole board; this procedure is recommended as a standard by the American Society for Testing Materials (.1). In general, the results of the tests are directly comparable since the tubes gave very consistent results.18 2. DISCUSSION OF RESULTS. Final weight less is considered to be the best measure of fire-retardant effectiveness because it is least . affected by Slight variations in moisture content, specific gravity and minor variations in the testing procedure. For theSe reasons the analysis of results tends to stress the final weight losses as being the best Mae fits. are recorded 1am through 25.. 7 " . 18. One of the advantages of the fire-tube method is that the tests can readily be duplicated. -28- available criterion of fire-retardant prcperties. The results of fire-tube tests of untreated and Series I material are shown in Tables 9 through 14 and for Series II material in Tables 15 through 20. Retentions, specific gravitieslg, and moisture contents were calculated as described previously. The figures for weight loss, temperature, and the other measures given are the averages of five specimens chosen to represent the whole board as shown in Figures 1 and 2. The boards in each table are arranged in order of increasing retention of dry salt. Examination of the tables shows that the per- formance of the specimens in the fire-tube is with few exceptions in the same order, that is, that weight losses and temperatures reached decrease regularly in the same order that retentions of dry salt increase. Thus, if the retention of chemical is known the fire-retardant qualities of the treated wood can be predicted with a high degree of accuracy. It must be pointed out at the outset that the Series I and un- treated material wes tested in a different fire-tube than was used in testing the Series II material. [A number of retests and comparisons were made to determine the effect of choice of tube, moisture content variation, specific gravity variation, and the chemicals used. These effects are investigated more fully in the following analysis of variance and covariance (pages 82 to 94 ). The two series are not directly comparable, but since such a comparison was not the purpose of these experiments, comparisons between species in either series are given. These comparisons are most easily presented in graphical form Figures 6 to 39, inclusive. Figure 30 shows the relative weight losses of untreated specimens for the six species studied. The curves are in the order of the specific 19. Specific gravities were calculatedfbnfthe basis of oven-dry volume and volume as determined by immersion in water. _ .....—_. .- BC. RE LCS 1.2;.‘14'1: Illa IT TH l9 TEN! L0 TI ;’ a D A TI D1» BO T34 T m Ma '4 fl 0 L I ma SJIIIIM I ’13 Lo DU! Na ma (“1‘ TI 1 DUE DUE t a C v a I 0 o h I o v a o I o v I O o v C O c .v {Fill BO. M . LO ,— .ar) -< "5... 3“ ' V. L03 TIM 1w :4 13* id to lar) '13 E; *3 ...‘l1 TI} lid >1ar) TIE Lid )lar) 5! -41- gravities of the specieszo, showing that a least dense species, yellow poplar, lost the greatest percentage of weight when tested untreated. White oak, on the other hand, lost the least percentage of weight and was the most dense of the species treated. The rates of burning as indicated by weight loss vary only slightly from.species to species. very little loss of weight for untreated specimens occurred after the burner was removed at the end of four minutes. moderate retentions of treating salts increased this weight loss after removal of the flame be- cause the flaming period was prolonged (Figs. 34 and 38). By referring to Figures 6 threugh.ll and 18 through 23 it is readily seen that final weight loss and rate of weight loss are directly related to the retention of chemical. There is a quite pronounced break in the curves for all species (except red gum where retentions did not exceed three pounds) falling somewhere between three and one-half and four and one-half pounds retention of dry salt. Because no definite standards of performance have been set down it is difficult to measure relative worth of various retentions. It seems evident that in general four or more pounds of chemical per cubic foot of wood are needed to lower the final weight loss to thirty per cent, or less, for Series I (Fig. 52). Slightly greater amounts of chemical (five pounds or more) are re- quired to give a weight loss of thirty per cent, or less, for Series II treatments (Fig. 36). An increase in retention above these critical points for either series has only a moderate effect in increasing the fire-retardant qualities. For example, in Figure 36, it is seen that an increase of chemical from 5.0 pounds per cubic foot (for yellow poplar) to 8.2 pounds per cubic foot was accompanied by a lowering of only six '55. The average specifichgravities based on ovenpdry weight and volume ‘were: white oak, 0.73; red oak, 0.70; maple, O;70; birch, 0.63; red gum, 0.623 and yellow peplar, 0.49. -42- and one-half per cent final loss in weight, despite the fact that more than fifty per cent more chemical had been added to the wood. It seems logical therefore, that for maximum.effectiveness and economy, treatments should be designed to give retentions only slightly in excess of the critical retention. Rate of burning - Untreated wood of all Species burned almost at the same speed and showed little variation in time and magnitude of maximum temperature reached (Fig. 31). Curves of temperature and time are presented in Figures 12 through 17 for Series I and in Figures 24 through 29 for Series II. A greater variation in temperature values was found than in weight loss values. This variation is probably attributable to differences in moisture content and specific gravity which have a more pronounced effect on rate of burning and maximum temperature than on loss in weight. In Series I with a moderate or light retention of dry salt, temperatures rose rapidly with a maximum appearing very near the time of removal of the flame (four minutes) or shortly thereafter. Yellow p0plar (Fig. 13) was an exception to this, probably because the low specific gravity of this species caused a more vigorous burning, with resulting maximum.temperatures reached at an earlier time. As the retentions increased the maximum.temperatures became lower and they were reached prior to removal of the flame at the end of four minutes time. ' .In the second series in which Wblman Salts Tanalith was added, the specimens burned more rapidly resulting in higher temperatures and a more complete combustion of the specimen before the flame was removed at the end of four minutes time. This tendency to burn.more quickly was reflected by a shorter period of flaming (duration of flaming after removal of the burner at the end of four minutes). Maximum.temperatures in Series II were reached in almost all cases before four minutes elapsed ~43- with all retentions (Figs. 24 through 29). In Figure 33 it my be seen that retentions of four pounds or more are necessary to keep maximum temperatures below approximately 300° C. for Series I. In Series II, on the other hand, approximtely five to six pounds of chemical are necessary to give the same effectiveness (Fig. 37). From these data on weight loss and temperature it seems evident that about four pounds of fire-retardant salts per cubic foot of wood is necessary to give highly effective protection from fire. Slightly more (five plus pounds dry salt per cubic foot of wood) chemical is required in the case of fire-retardant salts to which wood preservative has been added to maintain the same effectiveness. Duration of flaming - The duration of flaming for all species un- treated is shown in Table 21. With the exception of red oak, the species in Table 21 are arranged in order of their specific gravities. Reference to Figure 34 shows that flaming increases with low retentions of dry salt up to the point where about three pounds per cubic foot for Series I and four pounds per cubic foot for Series II (Fig. 38) are present in the wood. However, the duration of flaming for Series I material is appreciably longer than for Series II material. In the case of yellow peplar some of the specimens were completely consumed before four minutes time, and therefore no observations on flaming were possible. m - Table 22 shows that all untreated woods glowedm fortmore than three minutes. In figure 35 data on glowing for Series I are presented. The presence of small amounts of chemical in the oaks and yellow poplar reduced the glowing period to or very nearly to zero. However, in birch, maple, and red gun a considerable period of glowing was observed even with moderate retentions. For retentions over the 21. Glow is the duration of headescense fie wood tested, m ceased. SPECIES Red Oak White Oak Maple Birch Red Gum Yellow POplar SPECIES Red Oak Yellow Poplar White Oak Birch Maple Red Gum -44- TABLE 21 DURATION OF FLAnING OF ALL SPECIES UNTREAIsD Inn OF I‘m-51m IN HINUTL‘S 1.02 .78 .70 .51 .38 -.05 TABLE 22 DURATION OF GLOWING OF ALL SPECIES UNTREATED DURATION OF GLOW IN MINUTES 3+ 3+ 3+ 34 3+ 3+ -45- critical four pounds all glowing was reduced to a very short time or to zero. Figure 39 shows a much greater glowing period for Series II treatments. Here five pounds or more were necessary to eliminate glowing. This fact may be attributed to the presence of chromium and arsenic salts in Series II treatments which chemicals tend to prolong the glowing Itime (1?). §PEEE£Z.' If the presence of chemical in treated wood tends to in- crease the temperatures at which wood ignites, as has been pointed out on page 4, the time for this wood to reach the higher ignition tempera- tures should be increased. This delay in reaching ignition temperatures will partially explain why wood with.moderate retentions of chemical flames a longer time than untreated wood. As the retention of chemical is increased, however, the action of chemical upon charcoal formation is increased and the specimen is converted to charcoal with.a minimum of flaming, weight loss, and glowing. And since charcoal ignites at a much higher temperature than does wood substance, effectively treated ‘fire-retardant wood.will not flame but will only char when subjected to high temperatures. 3. ANALYSIS OF VARIANCE AND commutes.” Due to a breakdown and subsequent reduction of the efficiency of the dry kiln some of the Series I material was not dried within the tolerance of moisture content of 723% (see Table 21). Also because of an urgent need for the tube used in testing the first series and the untreated control Specimens, it was found necessary to burn the second series in a fire-tube that had been constructed by the Michigan State College machine shop accord- ing to the Forest Products Laboratory Specifications and blueprint. 22. For a dEScripticnfiof analysis of variance aid—oovEEIEBEe“eeo"“ ”“ “Paloma. n, and I. listed at the end of this report. DESIRED REJL'WI'W MID 3'1"th RETEII‘ICI?-ALL SPECIES 121333 — Rel 5:9. A Yellow Poplarfi “White Oak 1, Birch :; 7 b-——Haple 1: -‘ -—~Red Gum p .f ’ t O 6 .— _._.__..._————--——_-— l RetentiontPounda Per Cubic Foot 9. .‘ Actu I . ’l 5' 6 Desired Retention-Pounds Per Cubic loot u- p - Actual Retention-Pounds Per Cubic Foot ~47- rrsm 5. RESULTS OF TREATING-SERIES II Desired Retention-Pounds Per Cubic Foot DESIRED BIIINTIOH AND ACTUAL RITENTIONqALL SPECIES a .— LEGEND ,1 + Red on: E P Yellow POplar{9 -—~Vhite Oak C, ~---Birch 1% '7 h—mp 1e L: , ~—-Red Gum F / '/§ r- * ’1’ ’ 7 l / + / - A , t 5 \0 ,x / .X a . [O .l. t ' /‘ t , x e'_ .« , IK/ "' .,¥/ /ffi L S'/ y /" /;I f / g , 3 F'- /i * ~ I"; /"/’\, i Q/ L ’. a ,+ Zr- ‘,,x”*k\*\\ Q , ’pn \\ A)_, . / \ “i' + \e I r— . (I a 1 1 a l A l s l l l p z z s 9 5 ‘ -48- diod- _,_._'— L- w— oooo ooa-oeeae3 ea mesa _ --- -----o. 1 9 O ," . 1 .J my— D 0 Time in Minutes 1% :32“.:‘.-' ‘~~—“—-. “.... ‘._ _._-____‘__ a a..- ...--‘A‘ Loss in Veight-Per Cent '49-» nouns 7 TIM! AND IDSS IX WEIGHT YELLO' PQPLAEPSERIES I ,m/0 A ... I -- .0 L r” ‘ f g) In y— Q"! .- . .0 ‘ .__.- L. e 0 ° 9 r é. . O O b . ”~e O . 9* y r— ‘v 3 L ° ,. b '- [1' .0 ” I- . I 8 b O . O O a- M1 . -..3 2 8 _ e 4- ,, 'I .I, 1”" [mph _' (’7 “ I _' ,. p . V1.0. )- / - , OM"— f': l A L A l 1 l l L 0 ’ Z 3 9 5 e 7 Time in Minutes -5'O-¥ FIGURE 8 TIME AND LOSS IN HIGH! WHITE OAK-5231 ES I L as r- P /" . 74 .. _ / " F 0 e 50 - it. a e a b 8 ‘° . k e e “e r _ a d h- . g 0 o e d a 39 .. \‘Q 3 ‘Vo e A e b \. ’.--- . e; . a» - ' , . e 0 e e e ‘9’ I” ' 4 lo I- .- / “’6 g a {I A > . z” 3 .‘- ¢ // . ‘x ‘ It” + . . O I... L l A l l l A l I A l 4 5' 6 7 O l a I . 3 Time in Minute 3 *———————iIIlIIIIIIIIIIIIIIIII'Ill'lllllllllllllllllr -59- PICWJEI 17 TIMI AND WHAT'JRE BID GUM-513115 I p—— A y l 3 The in Minu‘es .,.,/‘:I 1 1 J I ‘I. a ‘ y I . /l)\ \ /4Me//° 1 /x/MM\QQ Cb .390 Ah I. it /0/ o o on I. I _ . _ . b _ — . h o . o . 005810.25!— canon Lou 1n Weight-Per Cont ~60- FIJURF. 18 TYPE! AND LOSS IE V3333 REP OAK-SEPIES II 3 The in Minutes 4» ~ *H "4 ¢,’—- /" 9 ‘0 f ; + /o ‘ 0 § f * f. t 1 1?“ +1; 9 . f t .51. 9 . * t g.» , - ‘I z + + Q ‘1 1 f 1' a" f 1» ' ,f I 1 1 J 1 A g . 1 1 2 5' 6 7 Loss in Vbighterdr Cunt -61- new 19 TIME LID LOSS I! WISH mwv rerun-sums II “ - b 4 + — *—' ' ‘”+ ,f‘ a — / // / + + /" * ’ f///¢“‘ 1+ ‘°%- b" r + a r—- P ¢ f + + " '. ’ ,1 / Juk- ‘ + + + + I- ‘.0;; ' ' * 1 t * 20L. *' 'd:; 4 + /(”N ¢Jyfl - + ‘ -, IO»— 1_. L V. J 1 + 1 . 1 ‘ 1 1 ‘00 ' 5' e 7 5 9 fine in Minutes Loan in Weigh‘-Por Cent [0 -62- FIGURE 20 TIMI AID LOSS II WEIGHT URI?! OAK-$13115 I! r + x. + / .4 » r/lé ’ i 01' A ' + / 4r / .«v . ,’9 f + t A" s. + ..L l 1 l «0* _ 3 4 Time in Minute: . .63- IIGUR! 21 TIMI AND LOSS IN WEIGHT BIRCH-SEE I IS I I «L b +U‘ r‘ ' ’l/ // ,5/ " "V \ o “ 1 1 1 1 1 1 . 1 . 1 1 1 O / 5 6 7 3 Mac in Minutes ‘1 a A J I I'I NI? 1 we no L035 a: mum an» BIAPLLSEPTES I! 3 ‘I 2110 in Minutos w h- . fi. ‘*- ...“— + 70-- + 1 + § + 1 r x + . + ‘l’ w L. \\‘ ‘f 1‘. I/' - V 1. / .if’ t’ 9 f 1 . __ ,- 1 f‘ E s.‘ 7 , / ~ I 1. ' a E x a" 550 - / 5 ‘ ‘ _ 1 / #3 I 1 ,‘x : i 5“, :w- .1/ 1" _ #1.... w + ‘ * , * 7.0]! Y 201- ; t x“ . .. +/ // 0 1- t/ A l A .1 A J A l l l 5’ 6 7 _ _ . _____ --...." __ , - ,1- .,_M-M_.. ...“ .4.-. ..-”...v...‘ . - - - - -. _. - L --—- -- - 0* " a ‘ ‘,- "’- " ‘5? ‘ .‘T ‘2 -‘z ...-9". 7-5 -1::9:-..w o’asoog ow... .-v‘.- m..- .. 1...... ‘7 mac-— z~o utx'd‘w 8’J‘L “2:51-133? 4:371- cc. \— cva-tum-flMvnw “...-5" -65- FIGURE 23 TIME AND LOSS In wEI3HT RED GUM-$28135 II 19 l 4%. Loss 11 woigh1-ror ccn1 1: 13 l I #45 \ A0.— 1‘/ I... + o L J L l A L A , “1' The ”in Minute—:96, §‘ Temperature-Dogroon C. if ..‘.. 1'7 .; :.:.-'.‘.. .13.. - ',~:.: :2. :;T."".——:m x 5‘; — 3-2-5— —A.:.t_‘.a:\ saga-... “....‘a.-. .5 ’IGURI 2“ TIMI1AHD TIHPIRATURI RID OAK-SERIES II --M ”3...... - -~-—.- (if 4rMT / 1- : +// +Iqr ‘\ 1-0‘ 'I 1L ”67513; \ +m' or‘ t ‘ I 4" * f ¥/ +, x/ i / ,9“ 11/ + + _ +m ; + +. * t .23’ ' + b 4. X 1 ‘5' + 1 .1 t .L A l L l A J J l A J I O I Z :7 6 7 ‘ 3 V Tile in Minutes Tonporaturo-Dogrcon 0. § § -67- 310031 25 TIII‘LID TIHPIRATURI YILLOI”?OPLAB-SIRIIS II \ m "‘\ 1\ i a “o +\_ . -: {if ~ i 0 L A J l l L 1' A J l o 2 3 9 5' 6 7 fine in Minutes “n la 00 a COLUtD‘IOLJJO EL OQBQF Tempora1uro-Dogroos C. 1mm 26 run up mm mm on-smxs n 7UU- P "r r .11 A. 355% \ _ r 1- 7' 4. “€- ,9: ' .1 tor {1’ f \‘g ,, \\ L. 4. \ A. 10;— / / n, . *‘w * f x/ \ *1! ./,/‘1 1 1 4-15" ,*- t \ * \ \1. _. k\ + + - 1“ 1 3. a l l 1 1 1 1 1 1 1 . L 0 I 2 7 5' 6 7 $11. ln‘Klnutos an .. ,1” T 5% x 1 "II/ | m .. 1:3"? ..-- ., I ‘ ‘-. 1/‘"’"'" t/ 11"" + 10*, r, ' . § “ ~.\ ‘ 1- ’ . | + ' + . 1 + _ ‘; ‘1’ ‘ufl . re - 194.9" Q, a ‘3 a _ * ~ g . 1. 0; n '— ‘ ,/’/4'*‘ ‘ 1. . . 8' ‘ o > 3* e- l" '- ,. ’ W7 1’: #11 n 1— ; 1’ *M’ / ‘K R . ¥' , Jx- 635’ + \ + I I Aancf I‘x *\‘ t 1 11* t i o l 1 1 1 1 11 1 1 1 L“ -59- FIGURE 27 TIME AND TEMPERATURE BIRCH-SERIES II The in Minutes ~70- ,IGURI 28 TIME AND TBQERAT’PE HARD ”Pu-SEI 55 II ”T ‘ " n1 +nf '1" \ .1 4, . K \‘ 1'13. ’13 Hint“, at ' f 1"" .. a Q J/ 1‘ 5n ' ‘ o‘ 9;; 6w 0 1 so f e 1‘1” . 5 ' r. 4; a; ’m /fl:flf+ :- O I” 1 1‘ "°“ ‘ a , ' ' n f/ »_ f 10" 4 i l A l L I J l .00 ' I z 1 -71- um; 29 111-1: 11:) TEMPERATURE RED GUM-SERIES II u .. _ \ m 1 " ”T r o ” fl “' “ 99" ,a‘/ \‘ 1515“ 9’. .1 H7 x . . /’/ + *‘:\ J‘DP- gfld' + ‘\ 1 ..‘. P b“ \ e § 0 8 W— I, a » / s . " -. + 1‘; K E“ 1 .1 - h 1 w 1 \ * 1 1 *x + “a l 1 I 1 l I I l l 7 00 2 5' 6 .3 5’ Tine in Minutes Idlvl {‘1‘}. I Loss in Weight—Per Cent TIME AF? 5132? LOSS-UNIREAI? -ALL SPECIES ‘ LEGIR? Red 0.2.1: 1’3 Yellow Paplar B wk’i‘nite CPS-t C, _-—Birch o g o _ 8 —--Hard Maple 1: ’ 1)”... ”W . -—Rod Gun 13 .-? ’ O . . 0 ' I O’p/ _ /'e . . O ._.. l e ' e .4 . . o’ “r, , o1 ' .f , f K/ ‘ l A l A l I l I z 5 II 5 fine in Minutes ‘ mm 31 TIME AND mmmnn—m SPECIES attire-Degrees 0. Tempo: mm —- Red Oak 9 Yellow Poplar B '-—Ihite' Oak 0, ""“ ‘Bil’Ch I/ ~31“ Maple 5 h M h F 'bo _ h 1, \' . ,- HT -"/ ' 1 1 x . C,/\ _ ’"f \\ a b 7' ‘31); 52. 0.1 kg .1 »_ - _‘ e -. .11 -.. ”1,31 I 1“ \\ b ;' T . T r" \ “1. ,v ’T‘ 'w a A V a 3‘ \ ‘. I 111', X ‘ A 500 .. o ‘4. t'!’ . I, [A 1.‘ F V ’ 6 o. . Q 1 W -— x . '\ 1‘ O P .1/1 \ ' o" r ‘ aw - b .\ be " ./ 18 .- “ 1‘1 ./ IA" \ f . r- r/ /‘ IL) ’ I ‘ . . o I“ C/ 1 1: C 1 P; - F ,/ zoo gm \ *9 9 1‘ 7‘ ' 4 n g '0 l g a L l L l A l A J A l I A 1 0 I 2 5 6 7 Time Bin Kinutee 1,! Final Weight Loss-Per Lien! A V, ._. ,_“_~.~_.«_~._ -— .--1--A___ 1mm 32 mm. mama? LOSS 1119 321mm: ALL snows-suns I mm Red Oak Yellow Poplar — -‘ Vhite ‘03.}: —- Birch —— Hard Maple ———Red Gu- Tme/PO‘D 1 l . I 1 l 1 I 1 l . l 2 3 ‘I 5 Dry Salt Retention-Pounds Per Cubic root ~75- ns'mz 33 KAXIMUH wzmzm'rm m 33:33:31: ALL SPECIES-SERIES I Dry San Retentioano-unda Per Cubic l'oo‘ mum ‘ - ~Bod on: H Yellow Paplarifi “Vinita Oak (L Birch D ~— Rod Gun F 1!!) Al @ °~~‘9 \ ‘A Q ~.(’ . . " ‘M -- . 9 ° E \K O O _ ‘ . r \ O .. < D ’, , o 4 . o 5. 0 3 no - ‘ 9 \\ (I . I; E. o m "' c: a O I r a ’ . ¢* . 8 . o , E“Jao'— o o a . \, 3 .v v o a u '- 0 0 '.° fllD- b l l 1 L A l A l I l. 00 I z 3 q 9 Durnti an o f Flaming-Minutes: 2'5 .3 TBA? If); I" 1L1) 33.73;?! 33 FIJHIFG ‘. ALL SPECX'S-SEIES I 193330 _ 'Red Cak Yellov Poplar ——Whito Oak +-——Blrch —n-Hard Maple ---A':’.ed Gun " ‘ t « ; T‘WuC’FmD / — ‘/ , O \ ‘5, / y //l \\ " y .. Q ff . D // I ’ ‘1 . . V ‘\\ h / \\ ‘\\ /’ \ flat 7;) \i‘ -_\ >— \ W '- / /’ \_ / l/ \\ R \a C O . ‘2 O . O \ b . . \ _ i9 0 .. . 0 U . J . 1 . 1 . 4 . - 1 L 1;. - \‘j p I z 3 ‘Y ' 5 c " 5 Dry Salt Rotation-Pounds Per Cubic foot ,— AJ—a-n.-——c—-—_-.._._._.__‘._____- 44—— ’ iipw fig” 1... -77- noun 35 DURATION or 01.0! m 23mm: m Stuns-suns I I mm ~ Bad on: Q Yellov Paplar B “White Oak C" .10 ~ 0 -* Birch D, -——-Hard Marlo <2 .\ r'// \‘\' x ‘ / '°. 0 I \ . X 0. ‘. g ‘5 H ‘ . x I L. g 3‘ .b. ; S "5" p 1'} u o n b O 2 \ a 9 -- .- 2 to b ‘ ' o o r- . \\ - D \ A \ M '- b o \'\ ‘ p x .. | 09 3 , f’ 6 O ‘ Kin“ fil‘5.C..D‘ E 00 A I d H z 3 Y 5' 7 Dry Salt actuation-Pounds Par Cubic Foot Mom 36 mm. WEIGHT 1.035 mm mm: AL; srmzzs-smms 11 -——~--.—,_.--,, 7 - ,¥_ z 3 If 9’ Dry Salt Retention-Pounds Per Cubic l'oct. mm Yellov Paplar 5 , —--— White Oak C‘ * f 6% ' MI I? f“ " "-Eaad Mag. 6: v \ + + - _ 0 + ' *- , L - ‘ *J'f ”x, c: . \._., 0 r- 6 A \ L f v . c, \\ + “r I ! “ L ; E + ‘ i a so @— ' . . *3 6 ._ b \ x 30 *— ‘t \ . + - E P’ + + a: 0* + 20 >— L. I0 _ o l a l a l l L 1 l a l O 6 7 ~-79- FIGURE 37 anm Tau-rumm- mm 2323mm ALL SPECIES-SERIES II LIGEKD ~— Red on 0 Yellow Paplar 3 -~Vh1te Oak 9 --Blrch 3 -—-Hard Maplc E ———Rod Gun r 1w #- E / *F"; I ‘3‘ 4.. \ ’ ¢” \\a 6 _ m "' *p ‘.+ 0 . ' 3a 9 t. \ b ‘p \\ \ \ x \ ‘t inn WQ' 0 \ '\\ o ‘ ‘\ o ’ : + x a a 6m - + l g .- \\.\ + u x \ gm _. In c, g 4' v0 .- I? E 5 ‘ ‘1“ + IDOF- * 3+ ,- Ill- A A ~ 1 I I a l L J l l 00 1 5. 7 Z 3 9 Dry Salt Retention-Pounds Per Cable root ~80- ....4 A! 114.3: 3: v“ -.A‘. ... 0 ...‘0A .‘ -."H ‘ 3......o'54.‘ C: F-An.-.l-’ {‘73 f.--:“!.IJ.I ALL SPEZIES-SZTIES II L337?“ Red Caz Yollfw Pagler White Oak TI fink} (>07 D mo Birch Hard ”5719 i - Red 312 7 .257;_ + 2&)-— 3 . o) a a _ d , 2‘ z D + (.9 [If — 7‘1 ~ + 5!.“ 5 ' 4r!“ 5. L ”’5‘ 3 +’*‘ 'Q, \ F x' , \ 5 IO —— +v // F; I « '// , i ,» +-’ ' g r .L fi+ g l g .- 5 ‘I: + * * ~ ' $\\M ‘ K‘"\. i ‘ ‘+ f t +9‘ 5 0 A l 1 l 1 l A hx‘u A J l I * . ‘ D l l 3 \-“ q 5- 3f? Salt Retention-Poundsxfer Cubic root ‘/,/«/ - ‘x a _ .x 9 ”M. -+ P + k* 7" ‘V—TJV' r._YT‘_I—_fi. ——¢»—-—_~ -—;.—-.»---—-u—-a~emo fihw‘v V -81.. 11602! 39 DURATION or GLOW AND RETENTION ALL srxcrss-szazgs I: 34) ZJ'- 8 *& Flratlon of Olov—Nlnutes E L 4 1 Z ‘3 Dry Salt Retention-Pounds 4 J Y 5' Per Cubic root .T . LEGEND "“ Red Oak Yellow Peplar -‘—~wh1te Oak *-Blrch -*~Hard Maple —w~Réd Gun “~’-‘"‘w‘ “4"?“ A-'~.- wfiw-‘—~---— “-..—h-ow».—‘—~—u.~-..---. __... _ _ _ - (30333 W! C/ "TI ‘ Ill-‘1': I 151' I... \ 4n. 1“ .3 In“ -32- The two factors mentioned above, namely, irregularities in Incisture content and the use of different fire-tubes make an analysis and comparison of results more difficult. Resort was made to statis- tical measures of significance of results through the following analyses of variance and covariance of the effect of moisture content, specific gravity, and the two tubes upon the final weight loss. The final weight loss was taken as being indicative of the effectiveness of treatment because it can be readily seen that final weight loss is closely correlated with the retention of chemical (see page $56. First, a direct comparison and analysis between five specimens of Series I and Series II was made upon maple because these two series of maple specimens are more directly comparable in retentions. These values are presented in Table I. Naturally it would not be wise to compare species in.which the retentions of the two series of treatments were not similar. The two series of maple boards also differed in Amoisture content and a reasonable Spread of specific gravity was observed. Second, a direct comparison and analysis between two groups of three specimens of birch (Series I) tested in each of the tubes were made. The comparisons Ihawn in Table 27 are made upon matched speci- mens from.the same board except that the moisture contents and the tube used were different. This analysis was to determine if there was a significant difference in tubes. fiesults_of first angly§i§_- From the ratio of the treatment mean ' square and the error mean square pertaining to moisture content in Table 2§, namely: 14 "(1) “its: it is seen that there are no significant differences between treatment = 0.306 means pertaining to moisture content. These averages are re3pectively: ‘ A‘ n $.11.“ .7 ...-fl ..rr'- .r—A v_ .... HMDB H WHHMMm ..I 33.2 7.69 HH HMDB HR mfiufiflm ARALYSIS 0F VARIAYCE ARD CCVAKIANCE -84.. OF THE lL-OISTURE CONTENT AND FINAL :dsIGHT LOSS mam-mime To HARD warm SUURCE CF VARIATION Total Tubes Treatment Error (Tube 1 Treat) Treat 4 Error Treatment Tube 8 Error Tube DF 13 MOISTURE CONTENT SUM SQUARES 79.00 50.50 6 6.85 6 21.65 12 28.45 7 72.15 MEAN SQUARE 5.31 50.50 1.14 3.61 TABLE 24 IRCD xy -454. 37 -128. 10 -339.57 13.30 “326027 -114.80 FINAL hT. LOSS SUM SQUARES 9587.34 325.02 9182.27 80.05 9262.32 405.07 BEAN SQUARE 9587.34 13.34 ERROR 0F bSTIMATE SUIk‘l SgUARES 71.88 5520.60 5448.72 182.53 110.65 DF 11 ...; EEAN SQUARE 14.38 908.12 110.65 F 63.2 7.69 Untreated l#=Ret. 2#=Ret. 3#rRet. 4fi=Ret. 5#=Ret. 6firRet. 8.0 9.1 9.3 9.5 9.7 9.6 10.8 This shows that the material was homogeneous as to moisture content at the time of testing. From the ratio of the treatment mean square and the error mean square pertaining to loss of weight, namely: (2) F = l§§§f§§ = 114.80 it is seen that there are significant differences between treatment averages of loss in weight. These averages are respectively: Untreated l#=Ret. 2#:Ret. 3#=Ret. 4#=Ret. 5#=Ret. 6#=Ret. 81.7 69.3 66.0 61.7 58.9 34.6 26.6 Since the value of F pertaining to treatment and error for moisture (F = .306) was not significantly different from.1, it is not necessary to carry out an analysis of covariance and adjust treatment means for slight differences in moisture content. The sIOpe of the regression line for predicting loss of weight from moisture content found from.the error-line of Table 24 is significantly different from.the slope of a similar regression line found from.the treatment plus error-line in the same table. This shows that the treatments affect the final weight losses; and these weight loss differences are not due to slight differences in moisture content. Furthermore, this difference in regression line sIOpes indicates that it is not necessary to carry out an analysis of covariance in order to adjust the treatment means for differences in moisture content. But, if such an analysis is carried out a significant difference between treatment averages after correcting for the same moisture content remains. On examining the ratio of the tube mean square and the error mean square pertaining to mmisture content, namely: (3) F :.§§1%9 = 13.98 -86- AhALYSIS 0F VARIANCE AND COVfifiIAfiCE OF THE SPECIFIC GRAVITY AND FIEAL hEIGHT LOSS PEHTAINIEG T0 HARD MAILE SDURCE 0F VARIATION Total Tubes Treatment Error (Tube 1' Treat) Treat 4 Error Treatment Tube 4 Error Tube DF 13 12 STECIFIC SUM SQUARES .0298 .0072 .0121 .0177 TMfldZS GRAVITY FINAL hElGhT LOSS ERROR CF ESTIKATE MEAN PROD zy SUM ELAN SUM DF NEAR F SQUARE SQUARES SQUARE SQUARES STUAKE .0298 1.615 9587.34 9587.34 .0072 -l.534 325.02 325.02 .0020 3.87 9182.27 1530.38 .00175 - .721 80.05 13.34 30.54 5 6.11 3.15 9262.32 8823.27 11 8792.73 6 1465.45 239.84 247.13 2 247.13 40.45 TABLE 26 ANALYSIS OF VARIANCE AI'ID COVAEIAIYCE OF THE SPECIFIC GRAVITY AND MOISTURE CONTENT PERTAINING T0 HARD MAPLE SOURCE OF DF SUM MEAN PROD. SUM MEAN VARIATION SQUARES SQUARE x2 SQUARES SQUARE TOth 13 79.00 79.00 043 .0298 00298 Tubes 1 50.50 50.50 .60 .0072 .0072 Treatment 6 6.85 1.14 -.10 .0121 .0020 Error (Tube x. Treat.) 6 21.65 3.61 -.07 .0105 .00175 Treatment 4 Error 12 28.45 -.17 .0226 Treatment 6 Tube 4 Error 7 72.15 4.53 .0177 Tube 1 -33- it is found that there is a significant difference between the means of the moisture content of the material tested in the two tubes. The F value of a similar ratio pertaining to loss of weight, namely: §5§=93 : 24.39 13.34 indicates that there is a significant difference between the loss of (4) F: weight means for the material in the two tubes. These F values suggest that it is necessary to carry out an analysis of covariance on these moisture contents and losses of weight data for the two tubes and adjust the averages of the loss of weight of the material in.the tubes for moisture content. Since it is impossible to tell from these two F values which significant difference is the more important, resort was made to the 810pes of the regression lines found from.the error-line and the tube plus error-line in Table 21. These slopes were found to be significantly different showing that the choice of tube, in this case, affects the final loss of weight. This significant difference in the slepes of these regression lines suggests that it is not necessary to carry out an analysis of covariance and adjust for differences in.moisture content of material tested in the two tubes. But should an analysis of covariance be carried out and these tube averages are adjusted for moisture content it would be found that a significant difference between the final weight loss means pertaining to the tubes remains. In a similar manner, analysis of covariance was made for final weight loss and specific gravity. The following F values were found from Table 215 for treatment mean square values and final weight loss mean square values pertaining to specific gravity, respectively: (5) F = &%%§$5 Z 1.14, not significantly different, and liggsgg 2 114.7, significantly different. F (5) shows that the material tested was homogeneous in regard to (6) F specific gravity. F (6) shows that there is a significant difference between treatment means. The slopes of ccrzesponding regression lines from Table 25 are significantly different suggesting no necessity of carrying out an analysis of covariance. But if an analysis of covariance is carried out, a significant difference in treatment means corrected for specific gravity remains. The F values were determined in a similar manner for tube means and specific gravity. The F values for tube mean square and for final weight loss mean square pertaining to specific gravity from Table 28?. are respectively: - 007 (7) F .0 - 325.02 (8) “13:34 4.11, not significantly different, and 24.39, significantly different. F (7) indicates that there is no significant difference between the Specific gravity of the material tested in the two tubes. F (8) indicates that there is a significant difference between final weight losses of material tested in the tubes. Hence, these F ( (7) and (8) ) values suggest that it is not necessary to carry out an analysis of covariance to adjust the final weight losses for slight differences in specific gravity. But if an analysis of covariance is carried out a significant difference of total weight loss in the two tubes after adjusting for specific gravity remains. The question arises as to whether adjustments of the loss of weight should be made for slight differences in moisture content and specific gravity. Equations were set up from.the error-lines and treatment plus error-lines, adjusting loss of weights for moisture content and specific gravity namely: y': y-‘h (x-i) - c (z-E). The coefficients, b and c, in these two lineS‘Iere significantly different, suggesting that it is not necessary to carry out an analysis of covariance of moisture content, Specific gravity and loss of weight and then adjust -90- the loss of weight for these variables. But if an analysis of covariance is carried out and treatment means of loss in weight are adjusted for moisture and specific gravity significant differences between treat- ment averages remain. These analyses show clearly that the differences between treatment averages of loss of weight are not dependent upon moisture content and specific gravity but upon the treatment used, that is, the amount of chemical retained by the wood. A similar set of equations were set up from.the error-lines and the tube plus error-lines, adjusting weight loss averages of material tested in the two tubes for its reSpective moisture content and~specific gravity. The coefficients, b and c, in these two lines were again found to be significantly different suggesting that it is not necessary to carry out an analysis of covariance for moisture content and specific gravity of the material tested in the tubes and than adjust the tube averages for these variables. But if such an analysis is made, a significant difference in weight losses between the tubes remains. ‘ This analysis then shows that there is a significant difference in total weight loss between the two tubes, but it is not indicated whether this difference is due to the use of the tubes or to the fact that the material in one tube was 1h.Series I and the material in the other tube was in Series II. To test this significance, an analysis of variance and covariance was made on birch tested in both tubes as previously described and as shown in Table 27. Eesgltsmofwsecond analysis - Ratios of treatment mean squares and error mean squares pertaining to moisture content and total weight loss were found as follows: (See Table 28) - (9) F = lfég = 1.33, not significant, and (10) F ' ll§2&§3 3 219.05, significant. 5.17 F (9) shows that the material tested was homogeneous in reSpect to ATE 104.7 1.67 I V 1 0 u e a v D 0 e I v V I p 9 a a o O i 4 e e I e a 4 v v v H as slams ANALYSIS OF VARIANCE AND COVARIANCE -92-'.- OF MOISTURE CONTENT AND FINAL WEIGHT LOSS PERTAIKING T0 BIRCH SOURCE OF VARIATION Total Tubes Treatment Error (Tube x Treat) Treat 4 Error Treatment Tube + Error Tube MOISTURE CONTENT DF 25 1 12 12 24 12 13 SUM SQUARES 113.50 88.62 14.15 10.73 24.88 99.35 MEAN SQUARE 4.54 88.62 1.18 .89 TABLE 28 PROD xy -489085 " 87014 -402 e 82 .09 -402 e 73 - 87.05 F IKAL U‘IT e SUM SQUARES 13738.29 85.69 13590.51 62.09 13652.60 147.78 LOSS MEAN SQUARE 549.53 85.69 1132.54 5.17 . ERROR OF ESTIMATE SUM SQUARES 62.09 7133.61 7071.52 71.51 9.42 13F 11 MEAN SQUARE 5.64 589.3 9.42 F 104.7 1.67 -93- moisture content. F (10) shows there is a significant difference be- tween the treatment means. These values of F suggest that it is not necessary to carry out an analysis of covariance, but if such an analysis is made, a significant difference between treatment means of final weight loss corrected for moisture content remains. Thb ratios of tube mean square values and error mean square values pertaining to moisture content and final weight loss were found as follows: (See Table 28) - (11) F = §§f§§ = 99.57, significant, and (12) F : Bétfa : 16.57, significant. F (11) shows that there is a significant difference between moisture contents of material tested in the two tubes. F (12) shows that there is a significant difference between final weight loss of’material tested in the two tubes. F (12) shows that there is a significant difference between final weight loss of material tested in the two tubes. These values of F indicate that an analysis if variance and covariance is necessary. When such an analysis is made, it is found that there is no significant difference for final weight losses in the tubes corrected for moisture content. That is, the choice of tube does not affect the final weight loss if the material is at the same moisture content and is similar in all other respects. This was the case in birch where specimens were chosen from the same board. The results of this analysis when applied to the results of the analysis on maple show that since there is no difference in the final 'weight loss between the two tubes, the difference noted in the case of maple must be due to the addition of'Wolman Salts to the treating solution since that is the only remaining variable factor that has not been adjusted for. Summary of conclusions on the analysis of variance and covariance of —-a—- -——_, -9 4- final weight loss forghard maple and birch - The following conclusions may be drawn from these analyses: 1) The material tested in each tube was homogeneous for that tube in regard to moisture content, but the moisture content of the material tested in Tube I was significantly different from the moisture content of the material tested in Tube II. 2) All of the material tested in both tubes was homogeneous in regard to specific gravity. 3) In all cases there were significant differences in final weight losses for the different treatments. That is, the total weight losses for the different retentions are significantly different and do not need to be adjusted for slight variations in moisture content and specific gravity. 4) A significant difference in final weight losses between the two tubes is found, but an additional analysis shows this difference to be due to the differences in material rather than differences in tile tubes themselves. The direction of these differences are best shown by the graphs of comparison of the various treatments (Figs. 6- through 39 )0 SUlfl\-'ARY 41:1) concwswhs _.— -4“ Although wood cannot be rendered "fireproof", it can be treated to make it highly fire resistant, as evidenced by the fact that effective fire-retardant wood will not contribute to its own combustion and will cease to burn and glow when the source of heat is removed. The data here presented are concerned with the fire-retardant qualities of six hardwood species: red oak, gugrcuswborealiswyighmg, yellow peplar, Idriodendron tulipifera Lt,'white oak, Querguswalba RL' -95.. birch, Betulapsplnyich§,, maple, £933;§EEE§E£H§;§§§§EB’ and red gum, .Iii.au}fi.aabe£_.sfog/32031119- .12 , These six species were treated by pressure method in two series with different mixtures of chemicals: the first to render the wood fire-retardant (the treating solution.used consisted of 60% ammonium. sulfate, 20% boric acid, 10% borax, and 10% diammonium.phosphate), the second to render it highly decay resistant as well as fire-retardant (the treating solution used consisted of the above mentioned fire- retardant solution to which Wolman Salts Tanalith, a water-soluble wood preservative was added). Treatments were carried out to attempt to give retentions of dry salt in these woods from.one to six pounds per cubic foot of wood. Actual retentions were variable because the species varied consider- ably’in density, porosity, permeability, and amount of sapwood present, and because of variations in these prOperties within the same species. Treated boards were tested in the Forest Products Laboratory fire- tube to measure their fire-retardant qualities. Results of these fire-tube tests thawed that: 1) Final weight loss varies with specific gravity; less dense species are more completely burned than heavier species. 2) As the retention of chemical is increased final weight loss, rate of burning, and maximum.temperatures decreased. 3) In wood treated with fire-retardant solution, about four pounds of chemical per cubic foot of wood are necessary to reduce weight losses to less than thirty per cent and maximum.temperatures to less than 300° c. 4) In wood treated with fire-retardant salts, plus preservative Tanalith, about five pounds of dry salt per cubic foot of wood are necessary to reduce weight losses to less than thirty per cent and ~96- maximum.temperatures to less than 300°C. 5) The period of flaming (time flaming continued after four minutes of test) increases with retentions of salts up to about three pounds per cubic foot and then rapidly decreases to zero. 6) Glowing (period of incandescense) decreases as retention of dry salt increases. -97- TImvpgmvog Glenn (1) American Society for Tezting Materia s. Tentative specificctions for fire-retardant properties of wood scaffolding and shoring. Designation Cl3“-37T. American Society for Testing Kateria s. 1937. (E) . Tentetive method of test for fire~ret3rd3n . ,r’ . e . properties of wood. Designation C loO-UlT. American Seeiety for Tasting Kateriols Standards Sujzlement II: 281-285. lEMI. (3) . Report on comparative fire tests of treated and untreated wood. Proceedings American Society for Testing Materials, M2: 233-276. ions. (M) .Americcn Hood Freservers' Association. Report of Committee 9- .ing. Proceedings American Wood Preservers' Association, 36: H: O—h '1 a; "(J '1 O O "b 392-h02. leho. (S) . Report of Committee 9—fireprcofing. Proceedings American Wood Preservers' Association, 38: “SE-MSZ. lENE. (6) Andrews, L.K. A study of fireproofing standards for pressure- treated lumber. Froceedings.American Wood Preservers' Association, 33 h62—us1. 19kg. (7) Eaten, Villiam D. Elementary mathematical statistics. John Wiley and Sons, Inc., New York. 1938. (8) Boulger, G.S. Wood. Arnold Press, London. 1908. (9) Brown, H.P. and A. J. Panshin. Commercial timbers of the United States. McGraw—Hill Book Co. Inc., Yew York. 1930. (10) Decry, Harold T. Equilibrium moisture content of salt-treated wood. Technical Publication F0. 58, Ken York State College of Forestry, Syracuse, New York. l9hl. (11) Electric Fireproofing Compeny. The record of fireproofed wood. -93- ,Els ctric Fireproofing Company, Yew York. 1900. (12) Federal Standard Stock Catalogue IV, Part V. Pronosed specifi- cation for fire—reterdsnt chemicals for grossure ingregnation of structural lumber and trcetment. Designstion TT- ?.-unnnnbered. lens. (13) Goulden, C.H. Kethods of statistical analysis. John Wiley and Sons, Inc., New York. 1939. (1%) Hcrkom, J. F. and J. I. Dore. Slow combustion te t. Proceedings Am.ericen 'u'ood Preservers' Assoc Htio ,29: 87-107. 1933. (15) Hartman, Ernest F. Fire-retardant treatment for wood, sym;osium on wood preservsticn. Proceedings nericen Society of I'echanical anineers: “DI 55-1—l.1,33. (16) Harley, L.F. and Louis E. Vise. The chemistry of wood. Chemical Catalog; Com,any,1~?ex-;York: 137-13. 192-6. (1?) Hunt, 3.”. and G.A. Garrett. Wfiod pretervation. NCGraw-Fill Book Co. Inc., New York: 397-U21. 1938. (18) Moore, 0.3. Distribution of s ”1t after kiln—drying. Pore t Products Laboratories of Canada, Cttm-rs, Canada. 193.6 (19 1% ticne l lumber Manufacturers Associetion. Pictorial review of hanger fire tests. Ustional umber Lanu fe cturers Association, Yoshington, D.C. 193C. (20) Prince, ..3. Tests on the inflamm ability of untreated wood and mood treated with fire—retrrde :nt confounds. Proceedings .Tationel Fire Protection Association, 19: 108-158. 1915. (21) Snedecor, George W. Statistical methods applied to superiments in agriculture and biolOgy. Iowe Ctzte Collefi Press, Ames, Iowa. 19U3. (22) Storm, Po eymond J. Firesefe lumber. Transactions American Society of ‘;echenico l ‘ngineers, 52 nt. 2: WEI—EE-Ma: 23-33. 1930 fi -99- (23) Truax, T p and C.A. Harrison. Meeturing fire recietance of 0“. wood. Transactionq American Society of Mechsnical Engineers, 52 pt. 2: wax-se-hb: 33-U3. 1930- (gh) . A new tert for measuring the fire resistance of wood. Proceedinge American Society for Testing Xeterirls, 29: 973—388. (55) United States Forest Products Laboratory. Fire-retarding gaints. United Stetes Forest Products Laboratory Rimeogrggh $1280, Hedison, Vieconsin. 19M1. (26) . Borax fire—retsrding paints. United Stetee % 1! r- " ‘0 9,0 Forest :roduct: Laboratory nimeOgragh Eli2», Mauieon, .iéconsin. l9u0. (£7) . Directions for the set up and 03erction of the Forest Products fire-tube. Unite: Stctes Forest Products Leborctory Kimeogragh “0’“ Madiecn, H sccnsin. Lo date. -../vs], (2e) Yitruvius. The architecture of Mercus Vitruvius Polio. Lockwood, Iondon. 137M. (23) Weiss, Hovzrd F. The preservation of structural timber. McGraw- J Hill Book Co. Inc.,,New York. 1315 ~100- eases DISTRIBUTION OF CHEHICALS IN TREATED MATERIAL Moore (18) found that the chemical impregnated into wood by pressure treatment is not evenly distributed throughout the wooden member. This gradient of chemical varies with such factors as size of specimen, method of treatment, density, sapwood and heartwood. and Species concerned. In these experiments the behavior of some of the treated material led the writer to believe that a similar gradient existed even when treatment concerned relatively small boards such as were here used (46" x 7%" x 3/4"). In an attempt to give a numerical measure of this unequal distribution of chemical throughout the wood, resort was made to the following analyses. Because of the number of tests involved only one board was analyzed. Piece 5M1 which had a dry salt retention of 5.00 pounds per cubic foot of wood was chosen because maple is of average treatability and because this board showed a retention sufficient to effectively . render it fire-retardant. The board was cut into fire-tube specimens (46" x 3/4" x 3/'") numbered as shown in Figure 1. Blocks approximately three inches long were chosen and numbered as indicated in Figure 40. Each of these blocks was then cut into two portions as shown in Figure 41, and identified as A or B for the outside and inside respectively. Duplicate analyses for phosphorus were then run on each of these eight portions and four check analyses were made on untreated maple of ‘ approximately the same density for control. lgzggggggg - The ten samples were reduced to fine shavings with a pocket knife and were placed in an electric oven at 104° C. and oven- dried. After cooling in a desiccator oven-dry weights were determined to the nearest tenth milligram. The samples were then reduced to ash 131793 1.0 LOCATION OF SAMPLES II" all “'2 -101- FIGURE ‘41 C'IT'I‘ IIIG DIAGRAMS A-Samples 1 . 2. 3 . and 1‘ 5/‘9/ FIGURE 3+2 CUTTING DIAGRAM FOB MOISTURE GRADIENTS 4-310 ‘ ' \ \ \ \\ \ \ \ \ \\ I z slylylo 7'16 vlglullzla fills] ‘5; ’ ' ‘ 45" - * - -102- by the magnesium nitrate method in an electric muffle furnace heated to 550° 0. following the standard 0.A.C. methodl. A few minutes was sufficient time to reduce the samples to ash. (In these ashings it was found difficult to avoid foaming and subsequent loss of material; perhaps ignition of the wood without ng(n03)2 treatment in the muffle would be simpler). The ash after cooling was taken up in a small volume of water (approximately 5 ml.) and HCl was added in excess. The acid solution was then transferred to a 250 ml. volumetric flask and made up to the mark with distilled'water. Analyses were made on two 50-m1. aliquot portions of this solution as follows: 3 ml. ENOS'was added to the aliquot and warmed to 45° c. on the steam bath to expel HCl and part of the HNOS. Then Eflzofl'was added leaving the solution.just acid. To this warm.solution.was added 60 ml. of ammonium.molybdate solution and the whole Was allowed to stand cold overnight. The solution con- taining the ”yellow precipitate" was decanted through a filter and washed several times by decantation. It was washed repeatedly with 1% KNO3 to remove nitric and hydrochloric acids and washing was con- sidered complete when 10 ml. of filtrate would not decolorize l drOp of 0.1 N NaOH using one drop of phenolphthalein as indicator. When washing was complete the filter and precipitate were returned to the original flask and a measured excess of approximately 0.1 N standard NaOH was added. After dissolving the "yellow precipitate" in the NaOH, three drops of phenolphthalein indicator were added and the excess base back-titrated with standard 0.1 N HCl. Phosphorus was then cal- culated per gram.of oven-dry wood in the sample. The results of these analyses are shown in Table 29. 1. Association ofmbfficialuxgricultural ChemistsLb—Ufficial and tenta: tive methods of analysis of the Association of Official Agricultural Chemists. Third Edition. hashington, D.C. 1930. -103- TABLE 29 RESULTS OF ANALYSIS SPECIMEN NO. % PEOSPHCRUS (as P) PER GRAM OF OVEN-DRY‘WOOD 1A .0096 and .0103 1B .0091 " .0101 24 .0680 " .0676 2B .0479 " .0484 34 .0771 " .0769 SB .0478 " .0478 4A .0971 " .0968 48 .0694 " .0687 5A .1718 " .1702 53 .1030 " .0988 -104- Qiscussion of results - From.Table 29 it is evident that phosphorus was not equally distributed throughout the treated board. Sample 5 showed the greatest concentration of phosphorus, since end and side penetration of treating solution both contributed to its heavier re- tention. The inner (toward the center of the board) layer of sample 5 was quite lower in concentration than the outer layer which had been in direct contact with the treating solution. Sample 4 where end penetration again affected the retention showed the next highest retention of chemical. Again there is a noticeable difference between inner and outer layers (A and B) in amount of phosphorus present. Samples 2 and 3 showed similar retentions both in inner and outer layers. No differ- ence in amount of chemical was noted for the untreated control (1A and 18). These results show then that endwise penetration increases the absorption of chemical in the ends of treated boards and that a gradient of chemical retained existed in this board. Such a gradient probably also exists in the other treated material. MOISTURE GRADIENT IN MATERm TESTED ‘ In drying the Specimens just prior to burning in the fire-tube the question of moisture gradient in the specimens arose. To determine the gradient of moisture in these specimens a series of experiments were carried out in which a specimen (no. 6) from.representative boards of each species was cut into three inch blocks as shown in Figure 42. These blocks were carefully weighed immediately after cutting and dried to ovenpdry weight to determine their moisture content. The results are presented in Table 30. . -. From.these tables it can be seen that moisture content values are quitewerratic and no definite conclusions can be drawn. In some pieces r [1,, -106- there was a greater amount of water in the center than on the edges (ends) as shown by boards 302, 5Y2, 5W2, 6B2, and 3G2. In another group, less moisture was found in the center than at the ends (boards 202, 502, 1B2, 2E2, 4M1, and 1G2). A third group which includes the untreated boards and a few others of less dense species showed 9 uni- form.moisture content throughout (boards U02, 102, UYZ, 6Y2, UWZ, UB2, 1M1, 2H1, UGZ, and 602). Since the results show many discrepancies no attempt was made to interpret these tables. £05354 has {13.5w Apr 16 1946