Notes 4.3 Chapter 13: Fibers Types, Fiber Identification, and Analysis

Fibers Fibers are commonly found with burglary, assault, breaking and entering, hit and run accidents, etc. Fibers are commonly found with burglary, assault, breaking and entering, hit and run accidents, etc. Fibers can come from clothes, carpet, curtains, wigs, furniture, paper, etc. Fibers can come from clothes, carpet, curtains, wigs, furniture, paper, etc. They are everywhere, and therefore are very useful to forensic investigators. They are everywhere, and therefore are very useful to forensic investigators.

What are Fibers? The basic unit of raw material in textile production (threads, yarns, fabrics) The basic unit of raw material in textile production (threads, yarns, fabrics) Fibers can occur naturally or can be produced artificially. Fibers can occur naturally or can be produced artificially.

Natural Fibers produced entirely from plants or animals produced entirely from plants or animals –Animal fibers  Sheep – wool  Goats - mohair & cashmere  Camels – camelhair  Llamas- wool  Silkworm- silk  Rabbit – fur  Mink – fur…..

Natural Fibers (cont’d) produced entirely from plants or animals produced entirely from plants or animals –Plant fibers  Cotton - cotton  Flax – linen  Hemp - hemp

Man-Made Fibers Regenerated Fibers (Regenerated Cellulose) Regenerated Fibers (Regenerated Cellulose) – produced by taking natural raw materials like wood pulp or cotton and chemically altering them  Rayon  Cellulose Acetate (ping-pong balls) Synthetic Fibers (Polymers) Synthetic Fibers (Polymers) –produced solely using synthetic chemicals (often petroleum)  nylon  Polyester  acrylics

CSI Using Fibers (clothing, carpet, drapes, wigs, artificial turf, paper) Torn Fabric/Paper Torn Fabric/Paper –Fit together like puzzle pieces Chemical Composition Chemical Composition –make sure fibers are from the same generic class with infrared spectrophotometry (process of burning and detecting the colors produced in the flame) Dye Comparison Dye Comparison –Color comparison with microspectrophotometer or chromatography Microscopic comparison Microscopic comparison –color, diameter, striations, thread count, weave pattern

Identifying Fibers However, there are some simple tests which help greatly in distinguishing fabrics, the most common being the chemical tests and burning test. However, there are some simple tests which help greatly in distinguishing fabrics, the most common being the chemical tests and burning test.

Place a small swatch of each of the fibers onto a divided well plate. Place a small swatch of each of the fibers onto a divided well plate. To each sample, add a drop of the test chemical To each sample, add a drop of the test chemical Wait five to seven minutes. Remove the fabric with a forceps and rinse well in a beaker of warm water. Blot on paper towels and allow to dry. Wait five to seven minutes. Remove the fabric with a forceps and rinse well in a beaker of warm water. Blot on paper towels and allow to dry. Examine & record results Examine & record results The Chemical Test

Chemicals 1.distilled water 2.sulfuric acid 3.sodium hydroxide 4.chlorine bleach 5.Dupont fabric stain solution 6.Isopropanol (Rubbing Alcohol) 7.Acetone 8.Formic Acid

Different materials burn in different ways depending upon the materials from which they are made. Different materials burn in different ways depending upon the materials from which they are made. –the appearance of the burn –the odor given off –the size of the ash residue –the nature of the ash –The use of tongs to hold the sample is advised. Crucibles and lids should be used to contain burning samples and to collect ashes. The Burn Test

Cotton and Linen burns with a large flame burns with a large flame leaves almost no ash. leaves almost no ash. the odor, if any, is quite similar to that of burning paper. the odor, if any, is quite similar to that of burning paper. after the flame goes out, a glowing spark may continue to travel through the unburnt material after the flame goes out, a glowing spark may continue to travel through the unburnt material the ash retains the shape of the original material. the ash retains the shape of the original material.

Wool either smolder or burn with a very tiny flame either smolder or burn with a very tiny flame the odor of burnt hair or feathers is unmistakable the odor of burnt hair or feathers is unmistakable a gummy, beady, ash accumulates and forms balls along the edge of the burning portion a gummy, beady, ash accumulates and forms balls along the edge of the burning portion leaves much more ash than cotton or linen. leaves much more ash than cotton or linen.

Silk burns slowly and with a tiny flame burns slowly and with a tiny flame characteristic odor is also of burnt hair or feathers. characteristic odor is also of burnt hair or feathers. The ash is black and shiny and, along the edge of the fabric, forms into tiny brittle balls that crush easily when pressed between thumb and forefinger. The ash is black and shiny and, along the edge of the fabric, forms into tiny brittle balls that crush easily when pressed between thumb and forefinger.

Synthetics Rayon, made from cellulose will burn with a large flame Rayon, made from cellulose will burn with a large flame –ash will vary, depending on the kind of rayon. Nylon and other synthetic fibers do not burn Nylon and other synthetic fibers do not burn –Usually Nylon fibers melt, leaving a brown mass at the edge of the material.

Your Assignment Conduct a series of chemical and burn tests on these different fiber samples: Conduct a series of chemical and burn tests on these different fiber samples:  Cotton  Linen  Acetate  Nylon  Polyester  Wool  Rayon  Silk

Your Assignment The 9 different tests will involve testing fabric fibers with: The 9 different tests will involve testing fabric fibers with: –Acids –Bases –Stains –Organic solvants –Dyes and indicators –Water –Flame