‘3 3?. Hj‘s' .. . u." 931". N . . a..v:.«7£,.bw.n kn, 9%.: ‘ 3 k‘ . ‘1 ‘ y b. a? .. , 1......3 n»), A.. We. .1 tr. ,f a .2; .u e 57551193 This is to certify that the thesis entitled CHARACTERIZATION OF DENIM FIBERS USING VISIBLE MICROSPECTROPHOTOMETRY presented by DANIELLE NICHOLE ALBERT has been accepted towards fulfillment of the requirements for the MASTER OF degree in FORENSIC SCIENCE SCIENCE (we: X2142?) 5' Ma' firdf'essqf’ Signature I'i// 22 ‘7 I A Y 3 Date MSU is an Affirmative Action/Equal Opportunity Institution .UBRARY Michigan State University PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 6/01 c:/CIRC/DateDue.p65-p.15 CHARACTERIZATION OF DENIM FIBERS USING VISIBLE MICROSPECTROPHOTOMETRY By Danielle Nichole Albert A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Criminal Justice 2004 ABSTRACT CHARACTERIZATION OF DENIM FIBERS USING VISIBLE MICROSPECTROPHOTOMETRY By Danielle Nichole Albert Denim fiber evidence is often encountered at crime scenes due to the shedding and transfer properties of fibers and popularity of jeans. Forensic scientists are continually looking for new ways to characterize fiber evidence and increase its evidentiary value in a court of law. The purpose of this research was to examine different denims using visible microspectrophotometry and to determine whether or not denim could be characterized by dye color. Twenty-six samples of new pairs of jeans were used for analysis in the main study. Three pairs of new jeans and ten pairs of worn jeans were analyzed for the wash and worn studies, respectively. Spectra were compiled for each of these studies. The results indicated that denim could not be characterized by dye color using visible microspectrophotometry. While jeans visually look different, the actual dye (indigo) is quite similar or identical among jeans. ACKNOWLEDGMENTS I would like to thank Dr. Siegel for his continuous guidance and support towards reaching my career goal as a forensic scientist. I would also like to thank Cheryl Lozen of the Michigan State Police for her assistance with this thesis. Finally, I thank all of my friends and family who supported me during this research and all other endeavors. iii TABLE OF CONTENTS List of Tables ........................................................................... v List of Figures .......................................................................... vi Introduction ............................................................................. 1 Microspectrophotometry ................................................... 2 Textiles and Dyes ............................................................ 2 Literature Review ............................................................ 5 Materials and Methods .............................................................. 8 Collection ...................................................................... 8 Slide Preparation ............................................................ 11 Fiber Analysis ................................................................ 12 Results and Discussion ............................................................. 14 Conclusion .............................................................................. 17 Future Work ................................................................... 17 Appendix- \fisible Microspectrophotometry Spectra- Nanometers X-axis and Absorbance Y-axis ...................................................... 19 References .............................................................................. 1 19 General References .......................................................... 120 iv LIST OF TABLES Table 1: Main Study ................................................................... 9 Table 2: Worn Study ................................................................... 10 Table 3: Wash Study ................................................................... 11 LIST OF FIGURES Figure 1- Synthetic Indigo ............................................................ 4 Figure 2- Sample 20 Main Study ................................................... 21 Figure 3- Sample 44 Main Study ................................................... 23 Figure 4- Sample 3 Wash Study ................................................... 25 Figure 5- Sample 1 Main Study ..................................................... 27 Figure 6- Sample 2 Main Study .................................................... 29 Figure 7- Sample 3 Main Study .................................................... 31 Figure 8- Sample 4 Main Study .................................................... 33 Figure 9- Sample 5 Main Study ..................................................... 35 Figure 10- Sample 6 Main Study ................................................... 37 Figure 11- Sample 7 Main Study ................................................... 39 Figure 12- Sample 8 Main Study ................................................... 41 Figure 13- Sample 9 Main Study ................................................... 43 Figure 14- Sample 10 Main Study ................................................. 45 Figure 15- Sample 11 Main Study .................................................. 47 Figure 16- Sample 12 Main Study .................................................. 49 Figure 17- Sample 13 Main Study ................................................. 51 Figure 18- Sample 14 Main Study ................................................. 53 Figure 19- Sample 15 Main Study .................................................. 55 Figure 20- Sample 16 Main Study .................................................. 57 Figure 21- Sample 17 Main Study .................................................. 59 vi Figure 22- Sample 18 Main Study ................................................. 61 Figure 23- Sample 19 Main Study .................................................. 63 Figure 24- Sample 21 Main Study .................................................. 65 Figure 25- Sample 22 Main Study .................................................. 67 Figure 26- Sample 25 Main Study .................................................. 69 Figure 27- Sample 39 Main Study .................................................. 71 Figure 28- Sampie 48 Main Study .................................................. 73 Figure 29- Sample 1 Worn Study ................................................... 75 Figure 30- Sample 2 Worn Study ................................................... 77 Figure 31- Sample 3 Worn Study ................................................... 79 Figure 32- Sample 4 Worn Study ................................................... 81 Figure 33- Sample 5 Worn Study ................................................... 83 Figure 34- Sample 6 Worn Study ................................................... 85 Figure 35- Sample 7 Worn Study ................................................... 87 Figure 36- Sample 8 Worn Study ................................................... 89 Figure 37- Sample 9 Worn Study ................................................... 91 Figure 38- Sample 10 Worn Study ................................................. 93 Figure 39- Sample 11 Worn Study ................................................. 95 Figure 40— Sample 12 Worn Study ................................................. 97 Figure 41- Sample 13 Worn Study ................................................. 99 Figure 42- Sample 14 Worn Study ................................................. 101 Figure 43- Sample 15 Worn Study ................................................. 103 Figure 44- Sample 16 Worn Study ................................................. 105 vii Figure 45- Sample 17 Worn Study ................................................. 107 Figure 46- Sample 18 Worn Study ................................................. 109 Figure 47- Sample 19 Worn Study .................................................. 111 Figure 48- Sample 20 Worn Study .................................................. 113 Figure 49- Sample 1 Wash Study ................................................... 115 Figure 50- Sample 2 Wash Study ................................................... 117 viii INTRODUCTION Forensic science continues to be an evolving field and new techniques are being examined to better characterize different types of evidence. Fiber evidence is often encountered at crime scenes due the shedding and transfer properties of fibers or, more generally, the ability of fibers to transfer from fabric to another surface. Denim fibers are commonly seen due to the popularity of jeans and other clothing containing denim. Denim can be typically defined as a “warp-faced cotton fabric, made from indigo dyed warp and undyed weft yarns” (Bajaj and Aganrval, 1999). Warp refers to the set of yarn that runs lengthwise and parallel to the narrow edge of woven fabric. Warp is intenIvoven with weft, or filling, which is the yarn running perpendicular to warp (Celanese Acetate LLC, 2001). Vrsual inspection of many different types and/or brands of jeans indicate slightly different colors. The observed color variation can be attributed to different dyes, bleaches, or other modification techniques. The purpose of this research will be to examine different denims using a visible microspectrophotometer and attempt to characterize denims by their dyes. VIsibIe microspectrophotometry has been chosen to satisfy both the need to further Characterize denim fibers and also the need to examine evidence efficiently. Visible microspectrophotometry requires less prep work than other instrumental methods and analysis is done in seconds. The significance of this research is that better characterization of denim fibers can increase the value of this type of fiber evidence. There are several classifications of fibers, most involving the polymer structure; however, dyes are able to further differentiate fibers and increase the degree of certainty that two fibers are associated with each other. Microsflrophotometgy Microspectrophotometry is a specialized form of spectroscopy and, therefore, is based on the same principles. Spectroscopy uses electromagnetic radiation to provide information on the atomic or molecular composition of substances. VIsible microspectrophotometry achieves this goal by measuring absorption or transmittance of wavelengths found in the visible light region in microscopic amounts of materials. Specifically, visible light interacts with the outer shell electrons in materials by exciting them to a higher energy level. Bonds and atoms present in a substance determine the wavelengths absorbed and how much energy the electrons will attain at the new level. Thus, differentiation between substances is achieved due to the differences in atomic and molecular composition. The wavelengths of light reflected or transmitted give items their color and often our eye cannot differentiate between similar shades. The absorbance spectra obtained from light and molecule interactions result in a higher sensitivity, which can aid in differentiating colored objects. Microspectrophotometry is usually coupled with computer software that graphs the absorbance or transmittance spectrum of the item being scanned. Textiles and Dyes The typical textile dyes used in denim manufacturing are vat blue dyes, natural or synthetic. Vat dyes are a “class of water-insoluble dyes which are applied to the fiber in a reduced, soluble form (Ieuco compound) and then reoxidized to the original form” (Hoechst, 1990). Vat dyes are known to be resistant to washing and sunlight, making them economically and fashionably desirable to be used on cotton fibers by denim manufacturers. However, indigo does not strongly bind to cotton fibers and will slowly be removed after continuous repeated wash and wear over a long period of time (Wikipedia, 2004). Vat dyes are applied to fibers using a dye bath. As stated earlier, these dyes are applied in a soluble form and then reoxidized to their original form. This reoxidation process can cause uneven dye distribution problems as the indigo dye molecules are “developed” to precipitate on both inside and outside of the woven cotton fibers, not necessarily evenly adhering to the surface of the fibers. Also, any jeans that have undergone any type of washing effects may experience “back staining”, which is color removal and redeposition of the dye onto the surface. The varying composition of cotton fibers and their lack of strong binding to the dye can also lead to uneven dye distribution problems, which may result in variation seen within one fiber or among many fibers (Bajaj and Agarwal, 1999 and University of Colorado, Boulder, Dept of Chem and Biochem, 2003). Indigo is the specific vat dye most widely used in denim production. Denim first became widespread in the 18th century when slave laborers and plantation workers needed clothes of good durability. From this time up to around 1900, natural indigo was used to dye the cotton fibers. Natural indigo is obtained from plants in the genus Indigofera in the tropics and from the plants woat and dyer’s knotweed in temperate climates. As synthetic indigo was being developed and improved, both it and natural indigo were used for producing denims. Today, synthetic indigo is almost exclusively used due to inexpensive dye production and more uniform concentration. Hence, it is possible that one cannot use instrumentation to differentiate between denim dyes. It is also possible that differentiation may be hindered due to the one dye component application in denim. Other dyes in fabrics are usually applied in mixtures of more than one component, making differentiation easier because of differences in dye chemical structures (Jeans My Age, 2004, Robertson and Grieve, 1999, and Wikipedia, 2004). Denim manufacturers generally refused requests for dye composition used in various brands of jeans. However, research indicated that all major denim manufacturers currently use synthetic indigo dye. Buffalo Color Corporation, a dye distributor, makes product information public. One such dye, synthetic Indigo NACCO is produced and analyzed as Indigo and is considered Vat Blue 1, number 73000 in the Color Index. Its molecular formula is C15H10N202 (Figure 1) and it has a molecular weight of 262.26. Its chemical name is 3H-Indol-3-one, 2-(1,3 Figure 1' Synthetic '"di9° dihydro-3-oxo-2H-indol—2-ylidene)-1,2, dihydro and its physical appearance is thin and dark blue. It may come in an aqueous paste, as the original water-insoluble dyes can be brought into solution through reduction in alkaline liquor (Derrett-Smith and Grey, 1967). As noted in the introduction, denim consists of cotton fibers. The composition of fibers can have an impact on the method of analysis used. It is known that natural fibers, including cotton, are composed of a variety of chemical constituents that are not distributed homogeneously throughout the fiber, unlike synthetic polymers (Robertson and Grieve, 1999). As a result, intra-sample variation is much more prevalent and the composition of a fiber has an impact on the visible spectrum. The chemical intra-sample variation, along with the dye distribution intra-sample variation may cause problems with differentiating fiber dyes using visible microspectrophotometry. Too much variation within a sample can make it difficult to distinguish differences between samples. Literature Review Fiber analysis has been a popular area of research within forensic science for many years. The initial method of analysis was simple microscopy using a comparison microscope. Analysis was expanded to include polarized light microscopy (PLM), Fourier transform infrared (FTIR) spectroscopy, pyrolysis gas chromatography (Py-GC), and uv-visible microspectrophotometry. Microscopic comparison allows examiners to evaluate differences in fiber diameter, length, shape (cross-sectional), surface features, color, and fluorescence (Robertson and Grieve, 1999). PLM and instrumental analysis examine the compositional structure of fibers, which are polymers. PLM takes advantage of the different effects seen with different polymers due to optical properties when polarized light is applied. Microspectrophotometry can be used to differentiate fiber color based on dyes and/or pigments. Differentiating dyes based on color has been researched with a variety of methods. Thin layer chromatography (TLC) was applied to fiber dye differentiation in 1981 (Resua et al., 1981). Resua et al. looked at dye extraction and classification from fibers using the separation solvent system of TLC. Other researchers later expanded on his work. High performance liquid chromatography (HPLC) has also been used to analyze dyes. TLC and HPLC are able to characterize dyes by separating out their various components. It has been found that dyes can contain different components or similar components in different amounts yielding a high differentiation of fiber dyes using HPLC (Joyce et al., 1982). Other methods for dye examination include FTIR (Ma et al., 2001) and Raman spectroscopy (Keen et al., 1998). The use of visible microspectrophotometry has been briefly examined and will be discussed in further detail below. Grieve et al. examined various fiber dyes in 1990 using visible microspectrophotometry and TLC. Concerning blue dyes, they found that only 0.24% of possible pairings showed the same absorption spectrum. If two different dye samples gave the same spectrum, they were considered a pair. These pairs were sulfur or leucosulfur dyes; thus, none of the vat dyes (dyes used in denim) exhibited this effect. As a result, it is reasonable to conclude that visible microspectrophotometry has the potential to discriminate among denim dyes. Grieve et al. also examined reproducibility among single blue dyed fiber samples and found one instance of peak reversal and eight instances (10% total samples) of maximum absorption shifts greater than 17 nm. Of these nine instances, four were vat dyes. While this indicates a possible reproducibility problem, it does not decrease the discriminating power of visible microspectrophotometry. These instances occur at a low percentage and with multiple scans taken, the averages could possibly even out. Multiple scanning of a single fiber is often a requirement anyway to account for uneven dye distribution and saturation. The authors' examination of fiber dyes using TLC yielded the following conclusions: there is often variation in the amount of discrimination possible among dyes, some dyes are difficult to differentiate, and the technique is limited by the difficulty of extraction. They also noted that samples are partially used or altered with the TLC method. In contrast, visible microspectrophotometry allows adequate discrimination consistently, involves no extraction, only a light washing to remove outside contaminants, and does not use up or alter the sample. Finally, the authors refer to reproducibility issues and suggest multiple scans per fiber. Overall, the study suggests that visible microspectrophotometry is adequate at differentiating among the dyes used in their research. MATERIALS AND METHODS Collection The denim samples used throughout the research were obtained from various retail stores. The fibers used in the main study were collected from five different areas per pair of jeans. Oral consent was sought from store employees in order to apply tape to the jeans. Scotch tape was cut into small pieces and used to tapelift the jeans. Each pair of jeans was considered a primary sample, while the tapelifts from the five different areas were considered secondary samples. A total of 50 pairs of jeans were sampled and labeled 1-50. The secondary samples were tapelifted from the front top area, back top area, front middle right leg, back middle left leg, and bottom right front leg. These were labeled as a, b, c, d, and e respectively. The tapelifts were put on transparencies to protect the fibers. There was one primary sample per transparency sheet. At the time of collection, a description of the denim, as well as sample number, store, brand, type, and materials/color were recorded in a lab notebook. This information was useful for identification and comparison. It should be noted that all 50 pairs of jeans were not analyzed. Upon analysis, the similarities seen in the spectra became evident and after samples 1- 22 were completed, the only other samples analyzed were samples 25, 39, 44, and 48. These four were added so at least one pair of jeans from each brand collected was analyzed. Table 1: Main Study SAMPLE # STORE BRAND TYPE MATERIALSICOLOR 1 Mervyns Levis 501 -W 100% CottonNint. Wash 2 Mervyns Levis 515-W 78% Cotton/22%Lycra 3 Mervyns Levis 515-W 100% Cotton 88% Cotton/11% Polyester/1% 4 Mervyns Lei Stretch, 85781821 DO2, 695556 Spandex/SB Drk Stn 5 Mervyns Lei Denim, 23921181002, 695956 100% Cotton/SB Drk Stn Hiphugger, 4W1698—style, 6 Mervyns Mudd 64938CW-cut 100% Cotton/Sand Blast Hiphugger, 4EGZ76-style, 100% Cotton/Sand Blast 7 Mervyns Mudd 63591CW-cut Coffee 8 Mervyns Levis 501-M 100% Cotton 9 Mervyns Levis 501-M 100% Cotton 10 Mervyns High Sierra 90798-style, 008335—cut 100% Cotton 11 Mervyns High Sierra Loose, RN48557, VN 372102 100% Cotton/Stonewash 12 Mervyns Lee Relaxed, 205-5591 100% Cotton/Classic Stn 100% Cotton/Pepper 13 Mervyns Lee Regular 200-8989 Prewash Curvy Ultra Low Rise, 14 Old Nay Old Navy VDN#300876823, 136771-00-1 100% Cotton 15 Old Navy Old Navy Low Waist Flare, 157536-00-1 100% Cotton Ultra Low Waist Boot Cut Stretch, 16 Old Nag Old Nay 184142-00-1 99% Cotton/1%Lycra 80% Cotton/18% 17 Old Navy Old Navy Relaxed, 171121-01-1 Polyester/2% Ltd? 18 Old New Old Navy Painters Jeans, 154696-02-1 100% Cotton 19 Old Navy Old Navy Number 7 Jeans, 401000-21-1 100% Cotton 20 Express Express Low Rise Flare, st1366, 0031 100% Cotton Precision Fit Low Rise Flare, 21 Express Express st1393, 0029 100% Cotton 22 Express Express Low Rise Flare, st2770, 0021 100% Cotton Precision Fit Carpenter, st1751, 25 Structure Express 0024 100% Cotton/Sand Blast 39 Gap Gap-M Carpenter, 174245-00-1 100% Cotton/Antiqued Marshall 100% Cotton/Md White 44 Fields Union Bay Loose Fit B00039, Y162726 Hot Whisker Marshall Polo Jean Woodrow Baggy Fit, 48 Fields Co. st7416YA12885, cut26211 100% Cotton For the worn study, samples were obtained from various pairs of jeans known to have been worn and washed at least ten times. The jeans were collected from various people, surveyed on the length of time the jeans were in possession and the approximate times worn and washed. The samples were collected in the same way as the main study, however, for uniform colored jeans, only one sample was taken and for jeans with fading, two samples were collected (faded and unfaded areas). Deviation from the five-sample collection was due to analysis results from the main study indicating that a specific area of jean did not affect the spectrum obtained. Table 2: Worn Study SAMPLE If BRAND TYPE MATERIALSICOLOR 1 Ralph Lauren NA 100% Cotton 2 Gap Flare 100% Cotton Express Extreme Flare 96% Cotton/4% Lycra Mudd Flare 100% Cotton 5 Express Low Rise Flare 100% Cotton 6 Express HJIJStel' Flare 100% Cotton 550 Relaxed Fit, 7 Levis Tapered Leg 100% Cotton 8 Old Navy Bootcut 100% Cotton 505 Lowrise, 9 Levis Straight Leg 100% Cotton 517 Lowrise, 10 Levis Bootcut 100% Cotton 11 Arizona Relaxed 100% Cotton 12 Lee Relaxed 100% Cotton 13 Lee Dungarees 74% Cotton/26% Fifi/ester 569 Loose Straight 14 Levis Fit 100% Cotton 15 Sonoma Carpenter 100% Cotton 16 Levis Silvertab 100% Cotton 17 Levis Silvertab Baggy Fit 100% Cotton 18 Northpeak NA 100% Cotton 19 Utility NA 100% Cotton 20 Lee NA 100% Cotton 10 Three pairs of newly bought uniform color jeans were used for the wash study. All washes were done using Tide detergent containing bleach. All washes were done using the same cycle (6 minute normal) and temperature (warm). Following each wash, the jeans were dried on the “more dry" setting and then rubbed in dirt to emulate significant wash/wear. The first pair of jeans was tapelifted after every wash with a total of twenty washes. A pre-wash sample was taken also. The final two pairs of jeans were tapelifted after washes one, five, ten, fifteen, and twenty. The difference in tapelifting method was due to prior examination of the first pair of jeans and the resulting findings. It was deemed unnecessary to tapelift after each wash, as there were no observable differences between fibers from each lift on the first pair of jeans. Table 3: Wash Study SAMPLE # STORE BRAND TYPE MATERIALSICOLOR 1 Express Express st1366, 0031 100% Cotton 2 Old Navy Old Navy Ultra Low Rise Flare, 200669-00-1 98% Cotton/2% Lycra 3 Meryns Levis 550 Relaxed 100% Cotton Slide Preparation In all three studies slides were prepared using the same procedure. Fibers were removed from the tape using tweezers and a scalpel and put on glass slides. Permount was used to affix the fibers in place and coverslips were put over them. The tweezers and scalpel were rinsed in xylene between samples to prevent cross-fiber contamination. The slides were labeled accordingly and placed in a labeled slide box. 11 Fiber Analfiis The analysis of fiber color or dye was done using visible microspectrophotometry. For this study, an SEE 1100 Microspectrophotometer and Grams 32 software were used. Before each day’s use, the SEE 1100 microspectrophotometer was calibrated using the National Institute of Science and Technology (NIST) filters. Absorbance was the method of measurement used for examination of the fibers. Calibration of the instrument was performed each day according to the following procedure. The instrument is first turned on and the light source is set to transmission. The computer is also turned on; the Grams 32 and SEE Image software are automatically loaded. Next, the reference filter is put on the stage and into focus, using the 20X objective. The microscope is adjusted for Kohler illumination by moving the field stop all the way to the right and using the condenser knob to illuminate an octagon with a blue halo. The field stop is then moved to the working position, two spots to the left. Next, the parameters need to be approved. The “autogain” button is pressed on the Grams 32 software and the parameters are noted. The “maximum y counts” may need to be adjusted so it falls between 3500 and 4000. To begin the rest of the calibration, a dark scan is first performed. This is done by closing the transmission shutter, selecting “dark scan”, and naming the file according to protocol under the calibration folder. A reference scan is next done by opening the transmission shutter, selecting “reference scan”, and naming the file according to protocol. The dark scan and reference scan files are then closed. The holmium oxide filter is placed onto the field stop to calibrate the 12 wavelengths from 280nm to 640nm. One selects “sample scan”, “% transmission”, and names the file according to protocol. Following the scan, the “NIST” button is pressed to check the values of the scan against the National Institute of Science and Technology (NIST) certificate values. The spectrum is printed for records. The same procedure is repeated with didymium filter, which calibrates wavelengths from 440nm to 880nm. Finally, the instrument is calibrated with three neutral density filters, which are utilized to measure the optical accuracy. They are expected to give a flat line or no optical response between wavelengths of 250nm to 1000nm. The three filters have optical densities of 0.1, 0.5, and 1.0. The same procedure as used for holmium oxide and didymium is followed except “absorbance” is selected instead of “% transmission”. Following satisfactory comparison to NIST standard spectra, the instrument is ready for use with samples. To begin analysis, a slide was put onto the stage and into focus. The aperture was then moved off of any sample fiber and a dark scan and a reference scan were run. Following these scans, five fibers were each scanned five times. The spectra peaks were marked, either by the computer software or manually. The final graphs include five overlayed spectra, one spectrum representing each secondary sample (taken out of the 25 spectra run). The reasoning for this is discussed in results and conclusions. The worn and washed study samples were analyzed using the same procedure, but the final graph overlays differ somewhat since not as many secondary samples were obtained. 13 RESULTS AND DISCUSSION The results indicate that the differences in visual appearance of denim fabrics on a whole are not due to different dyes. \frsible microspectrophotometry was unable to differentiate between multiple brands and types of jeans. The results also indicate that washing, even with detergent containing bleach, and wearing of jeans according to this study’s protocol do not affect the measured color properties. The figures in the appendix illustrate the similarities of the scans. The five scans of a single fiber were found to be similar so one representative scan from each fiber was sufficient. Upon comparing the five fibers from a secondary sample, one again noticed the similarity, narrowing down the required scans to one from each secondary sample. Therefore, the final graphs of samples from the main study contain five scans, one fiber per secondary sample to represent the primary sample. The graphs from the wash study also show five scans, illustrating the spectra seen from one sample after washes 1, 5, 15, and 20. The graphs from the worn study Show five to six scans depending on if the samples contain uniform color or faded areas. Those with faded areas are illustrated by six representative spectra- three scans of fibers from faded areas and three scans of fibers from non-faded areas. Although no major differences were detected and differentiation could not be achieved, there were some slight differences that bear explanation. Throughout the research it was discovered that the natural twists and concentration of dye in the fibers affected the resulting spectra slightly. A higher 14 concentration of dye can saturate the spectrophotometer detector. Twists in the fibers have the same effect. When the microspectrophotometer attempts to analyze the fiber, it requires transparency for proper absorption readings. Broader, rougher peaks result from scans of opaque parts of fibers (Figure 2). Normal scans of denim fibers result in a spectrum with a main peak at approximately 650-660 nm and a sharp decreasing slope from the peak. Normal spectra also have a shoulder around 540 nm that gradually leads into the peak, with no decreasing slope. Scans of twists and high dye concentrations show a flatter plateau beginning at the shoulder and extending to the main peak area, ending again with a sharp decreasing slope. These differences are thought to be inconsequential because the dye still absorbed light in the same area, but some resolution has been lost due to excessive absorption. This loss of resolution seen in high dye concentrated fibers contributes to the difficulty of using microspectrophotometry for differentiation among denims. Even if denims could be differentiated, there would still be potential problems with darker (more concentrated) denims—note that darker denims are not darker because of a difference in dye chemical composition, which would affect where the absorbance occurred, but rather they are darker due to a higher concentration of dye. Other slight differences among spectra were seen with peak heights. The y-axis measures the amount of absorbance or intensity. Again, dye concentration affects this aspect of the spectra. A more concentrated fiber or segment of fiber results in a higher absorbance (intensity) until it saturates the 15 detector. Differences of intensity were seen among fibers and within fibers (Figure 3). This variation can be traced to the dyeing process. Often, fibers will not have even distribution of dye throughout them. This variation is inconsequential because there is no way of using it to distinguish between denims due to the presence of intra-sample variation. It should be assumed that fibers do not necessarily have the same intensity within and among themselves even if they were obtained from the same garment. Since the most significant aspect of distinguishing fibers by true color is where the absorbance occurs, intensity can be assumed to have a trivial effect in this study. The position of absorbance, measured on the x-axis, indicates the exact color of dye. This study has shown that all denims use the same color of dye, and are most likely manufactured using the exact same dye, indigo. While the slight variations seen between spectra might seem advantageous in differentiating between the similar spectra, this is not the case. These variations were not just seen between samples, but were also seen within samples (Figure 4). One cannot use variation to distinguish fibers when the intra-sample variation is as just as great as the inter-sample variation. There might be future exceptions on a case-by-case basis if a large quantity of known and unknown fibers are examined and the intra-sample variation is found to be less than the inter-sample variation. 16 CONCLUSION The results and discussion indicate the difficulty in using visible microspectrophotometry to differentiate denims. As noted in the literature review, researchers have found this to be the case due to the natural cotton polymer, uneven dye application, and one-component dye used. This research supports the claims that visible microspectrophotometry has limited usefulness for distinguishing fibers from denim in forensic casework. This research also supports a study done in 1988 that indicated “the evidentiary value of blue denim fibers is necessarily very low" (Grieve et al., 1988). That previous study examined 30 samples originating from16 different brands of jeans and concluded that all samples produced similar spectra within a certain range. The research for this paper was controlled carefully by using only cotton fibers, calibrating the instrument daily, and avoiding any contamination that might have affected the absorption spectra. The general similarity of the spectra between samples in addition to the similar intra and inter-sample variation is responsible for the inability to effectively characterize denims based on their dyes. Future Work Although this study indicated a lack of differentiation among new, washed, and worn jeans, there are some suggestions for future research. None of the jeans used in this study were considered “decorated”. As styles become more outrageous, it is likely one will see denims with added components. One such component, already seen in stores, is glitter. Glitter powder is available from companies like Americos Industries Inc. for application to textiles. Denim 17 containing glitter may be differentiated from other denims using microspectrophotometry to analyze the glitter particles in addition to the fiber dye. Another avenue for future research is differentiating among denims with multiple fiber types and varying amounts of different fibers. Although, some of the jeans in this study contained polyester, spandex, and Lycra in addition to cotton, I only concentrated on analysis of cotton fibers to maintain consistency and control for differing polymer composition when running microspectrophotometry analysis. It might be possible to differentiate denims using dye and polymer composition using visible microspectrophotometry. However, this would likely require a large sample set, consisting of more than a few fibers. Often, collection from crime scenes or victims may yield only one or two fibers, limiting the practical application of results from such research. Finally, it is probable that ultraviolet microspectrophotometry may have a better chance of differentiating between denims encountered in casework. The reasoning for this is that jeans are washed with detergents that typically contain optical brighteners. These chemicals are fluorescent agents added to detergents to make clothes look cleaner. They work by converting ultraviolet light to visible light. As a result, they will absorb ultraviolet light differently than the dyes in the denim and differentiation of denims is possible due to the following variable factors among pairs of worn jeans: number of times washed, detergent used, and type of optical brighteners in detergent. While visible microspectrophotometry cannot characterize denims well, it is likely that ultraviolet microspectrophotometry can be useful for this purpose. '18 APPENDIX VIsible Microspectrophotometry Spectra- Nanometers X-axis and Absorbance Y-axis 19 Figure 2- Sample 20 Main Study 20 or com owa owe owe N 059“. 21 Figure 3- Sample 44 Main Study 22 occr 0mm can con L llE _ ocv /. ,..\ \r ,.. ..,., pf I/I / Mr, L p... z/.. Z .., a... rm. ... f. .._ .... r.- ., _... ,, _..__ _ . 4 — x. u . ,e,. . .l ; . . n? wmo IF /, J , __ . / f ,/ mmw=gmru E I. TN 23 Figure 4- Sample 3 Wash Study 24 02:. 2: E coo L own ~§ Ii IIII.IIIIIIIIIIIIIIII w 059”. .- , ' 0 J ~‘ / L .4.‘/{.$_ -, 41"— _-___ .1...._...;. _..___.-._—I o __.__-__I_ .- __-,- ”.4 z N 25 Figure 5- Sample 1 Main Study 26 coop cam com . r! _ \-II\\S \KEIE .3 . a . \qutwsu «Wmfltslxl I, a Lt ,Isl/ _ -._._. _._,_.—_mm R, flu‘ — - own @5500 coo TIL .iiIIIOIIIV com ocv _ A m 0.59". 27 Figure 6- Sample 2 Main Study 28 com E 2.: 2.5m can _ com A o 059.... 29 Figure 7- Sample 3 Main Study 30 98 r coo can 02. can can as _ _ 4 Ir 0 N 0.59“. fl 31 Figure 8- Sample 4 Main Study 32 32. com com 02. com com Gov _| F . .0 , \ Fm. r 33 Figure 9- Sample 5 Main Study 34 cos _ 2.5 8... oov . I m 059... 35 Figure10- Sample 6 Main Study 36 o8 37 Figure 11- Sample 7 Main Study 38 coop 8a can can as 8m 93 LI _ F r w _ 52:9“. Ell) IO \\\(V\ \E/ ,/r “saws“. a, \\, .\I\.\I\II\I\\,\II \SIIIII/I . 39 Figur012- Sample 8 Main Study 40 06°F owm mm” JWW coo owm 00' NF 2:9”. TIE... IE . . 1° \ {$9103 Ix] \z? \.\:\ \‘K \,\.\\..\.III\I\I \.\,. .\I\I1’IIII{\I\III\/\\I \I\ \II \J/‘/ u/ (WI/I .\ /,/ r, .r/ / I ..: , f a. {f .2 any. ,, 4...... / .2...» . . .fl/ MN“ m. nut nmm TV. z .. f ._2 , / H. _ ,/ :dmo . . h .,. To. 0‘30 TN. (‘I '0 41 Figure 13- Sample 9 Main Study 42 coo? i. o com com oov ems own o_k . c [IE 9. 059 m r o \ \(.\r\ \ \\.$I\\’I{I\u. (\IlIS/IIJIIIII ../ r I .a/ .3... . 4.. , ...,.. x, ”NJ. ( Arm , .,../. / , . 2. o s. .8 , V. .. ,, ,0. . /.. Tr / I In. F I, Nokmm 2,. a /. \ 3K 43 Figure14- Sample 10 Main Study coop com com 2:. com can 901 _T . F _ L F _ E m 3 2%: ,_._..———————-——- 45 Figure 15- Sample 11 Main Study 46 ooo _. ooh _ 8o own owe 9 2:9”. 47 Figure 16- Sample 12 Main Study 48 oov / 49 Figure 17- Sample 13 Main Study 50 51 Figure 18- Sample 14 Main Study 52 ooov oos L 2.3 oom ooe F; L 2 93mm 53 Figure 19- Sample 15 Main Study 54 ooow ooh C com com DOV t. F _ c a. 2., 2.2... \ a... .C/ a. ._... . z, , _ , I r / _ .. l \ M . . .1. mnsmo 2. 0.59m 55 Figure 20- Sample 16 Main Study 56 oom ooh . I l, 9.80 III ooo // Pom / III oov L] .. 57 Figure21- Sample 17 Main Study 58 coo? com F own ooh ooo H oom L cow as :\ 1,; K2 xi? 3i \xikr Slaw“- r . \) (\..\r\/\I\II\)\II \(I, u .. , \\ 3.. \ \r ;I‘\. . i . , l, x, x. I\ Y- \:\./.\r\ l\.\\.a\lr4\lavl'\\\ {\J) \f/S/w. .... z. .\ J r .. c . r\ K , . \.\\..\I\K /. 23 cm.» 2.... an 9:9". 95 Figure 40- Sample 12 Worn Study 96 2.: 2.3 2.3 omv cc 9:5 IN 97 Figure 41- Sample 13 Worn Study 98 ooo —. own 80 as L 3 2:9“. TN 99 Figure 42- Sample 14 Worn Study 100 coop ooa can can can con ocv IF _ _ _ r1 _ ~ we 9:9“. To g lrll\i\r\l\f\l\ U/ |\\r||\|.1\|l-|.\ \i)! I)‘ / J. z a r, J m.” .4 x. ,. .. .L ., .. 1 f/ ., , 47m , 1 0 1|. iv nvdno g Figure 43- Sample 15 Worn Study 102 103 Figure 44» Sample 16 Worn Study 104 2:. H can 3. 2:9“. 105 Figure 45- Sample 17 Worn Study 106 2 2.; 2% cm: 2% 2w... 2%. 9. 2:9“. IO .. I, ./ I, r. 13 8.58 IN 107 Figure 46- Sample 18 Worn Study 108 fl... ...\ um... .I. l r- ti... F .3! Lu 000—. 000 own 005 000 0mm 0%? 0 r . we 9:9“. To 1111/ \kl\\ \ \1\ .‘d‘n‘t‘bflflfig‘nI/illupllw‘ x»\m\\\\.ntlllllisll..rlll1l§1li {Ill / fififikg ”a; e,” I NOKmm a. .,,, ,. \ ,1», . /\ .3/ 2 m8 7—7‘-,- ‘-A_._...H_v______.+rr w .. 109 Figure 47- Sample 19 Worn Study 110 000 _. 2.: can own 09. S 2:9“. 111 Figure 48— Sample 20 Worn Study 112 ooh _ 0.00 113 Figure 49— Sample 1 Wash Study 114 o2: omm 2.5 fl . ‘. 0X\ :3“ ri‘l‘l)“lll\{(l’l\| \ng\.\\1\\a\i/ of com com cow 2 To :. 3.28 TDJ‘ r... \ /. (l \ x 2.8m TN 115 Figure 50- Sample 2 Wash Study 116 run-'- 002. com com own com com oov . _ p . 2 L on final fl $\.l\ls\\\y\.\H\\r/\II1I\‘IHI)I\I\IH1\H\1IH\1\1\11‘ II / {\\\u.\l\..\lxl\ll-sli.}( , \s.‘\\. \\V\\\§§k§.flwu V .\ \ .\,\\.\\i .\1\. I//.//, TN 117 REFERENCES 118 fall a.“ lull. in REFERENCES Americos Industries Inc.: hip:llwww.cosmod_yes.com/en_zymes-chemicals.html. Cosmonaut Chemicals, 2003. Bajaj, P. and Aganlval, R.: Innovations in Denim Production. American Dyestuff Reporter, 88: 26-35, 1999. Buffalo Color Corporation: http://www.buffalocolor.comfrndigo.html. Revision Date: 10/10/01 Celanese Acetate LLC: Complete Textile Glossary. h_ttp:l/www.celanes_e_a_1cetate.comltextileglossa_rv filament acetatepdf, 2001. Derrett-Smith and Grey: The Identification of Vat Dyes on Cellulosic Materials. Pergamon, 1967. Grieve, M.C., Dunlop, J., and Haddock, P.: An Assessment of the Value of Blue, Red, and Black Cotton Fibers as Target Fibers in Forensic Science Investigations. Journal of Forensic Sciences, 33(6): 1332-1344, 1988. Grieve, M.C., Dunlop, J., and Haddock, P.: An Investigation of Known Blue, Red, and Black Dyes Used in the Coloration of Cotton Fibers. Journal of Forensic Sciences, 35(2): 301-315, 1990. Hoechst: Dictionary of Fiber & Textile Technology. Hoechst Celanese Corporation, 1990. Jeans My Age: History of Traditional Indigo Dyeing. http:/fieansmy— age.netflndigo.html, 2004. Joyce, J.R., Sanger, 0.6., and Humphreys, |.J.: The Use of HPLC for the Discrimination of a Range of Dylon Home-dyeing Products and its Potential Use in the Comparison of Illicit Tablets. Journal of Forensic Science Society, 22(4): 337-341, 1982. Keen, l.P., White, G.W., and Fredericks, P.M.: Characterization of Fibers by Raman Microprobe Spectroscopy. Journal of Forensic Sciences, 43(1): 82-89, 1 998. Ma, H.C., Huang, Y., and Lei, H.: New Applications of FTIR-microspectroscopy in the Field of Forensic Science. Spectroscopy Spectral Analysis, 21: 468-471, 2001. 119 Resua, R., DeForest, PR, and Harris, H.: The Evaluation and Selection of Uncorrelated Paired Solvent Systems for Use in the Comparison of Textile Dyes by Thin-Layer Chromatography. Journal of Forensic Sciences, 26(3): 515-534, 1981. Robertson, J. and Grieves, M.: The Forensic Examination of Fibres (2"d Ed.). Taylor and Francis Forensic Science Series, 1999. University of Colorado, Boulder, Dept of Chem and Biochem: Supplement to Experiment 6, Essay: Dyes and Dyeing. http://orgchem.colora_do.edulcourses/3381 manual/DyeEssay 81504.mf, 2003. Wikipedia: Indigo Dye. MediaWiki, thpzllen.wikipe_dia.org_lwr_’killndigo dye, Last Modified 21 Feb 2004. General References Eyring, M. B.: Visible Microscopical Spectrophotometry in the Forensic Sciences. Forensic Science Handbook Vol. I (2“d Ed.) Saferstein, Ed. (Prentice Hall): 321- 387, 2002. Siegel, J.A.: Encyclopedia of Forensic Sciences. Acadamic Press, 2000. 120 u113111111111191111131