Eagles SciOly 2014: Crime Busters - Hair & Fiber


Terms in this set (...)

Classification of Fibers
1. In general, one can say that the smoother the fibers, the more likely they are to be man made.
2. Most of the fibers made from natural sources such as animal or vegetable fibers are shorter fibers that are twisted together in some fashion. This often has the loose ends sticking out that look like fuzz.
3. In a real life most clothing is made from a blend of natural and man-made fibers.
Strategy 1: Burn Test
1. Distinguish plant fibre (cellulose) from animal fibre (protein).

2. Materials
2a) fine scissors
2b) fine stainless steel tweezers
2c) unscented candle or other source of flame
2d) lighter or matches

3. Precautions
3a) Burn tests should be carried out in an area safely away from artifacts and combustible materials.
3b) Fiber samples produce little smoke but, before carrying out multiple tests, verify that doing so will not accidentally activate smoke detectors.
3c) If using matches to light the candle, let the odour of the lit match dissipate before beginning the burn tests.
3d) Practice the technique with known samples from an expendable textile before doing the test on yarns from an artifact. It is important to gain experience in making observations by sight and smell at each stage of the burning process.
3e) Be aware that the flame will consume the fibres extremely quickly and, because the samples are very small, the burning fibres may be difficult to see.

4. Procedures
4a) Holding the fibres or small yarn sample with the tip of the tweezers, just above the flame from something like a match. It is important not
to let the flame touch the fiber itself. note the following:
4b) visual observations as the sample is brought near the side of the flame, in the flame, and out of the flame,
4c) odor as the fibres burn,
4d) characteristics of the ash including the colour and texture.
4e) The man-made fibers will decompose and melt
much quicker than either the animal or vegetable fibers.
Strategy 2: Bleach Test
Yet another way of separating the animal fibers from the vegetable or man-made fibers is to put the fibers in regular household bleach.

The animal fibers will dissolve, but the man-made and vegetable fibers will remain untouched.
Strategy 3: Microscope Observation
1. Microscopy can be used to confirm the results of burn tests, and will make more sense of the results from burn tests on blended yarns. Microscopic examination also helps to distinguish cellulose fibres from protein fibres. Fibres in poor condition, very dark fibres, and those with surface finishes may be difficult to identify with a microscope.

2. Materials
2a) compound light microscope (up to 400× magnification: 10× eyepiece plus 10×, 20×, and 40× objectives); minimum recommended magnification is 100×
2b) microscope slides
2c) microscope cover glasses
2d) microscope slide trays or holders
2e) small beaker of water or mineral oil, to use as a mounting medium for temporary slides
2f) fine tweezers
2g) eye dropper
2h) fine scissors
2i) permanent marker and/or pencil, for documentation

3. Procedures
3a) Using fine tweezers, place the fibers in the centre of a glass slide that is free of ontaminants such as other fibers.
3b) Tease the sample fibres apart with the tips of the tweezers. To simplify identification, the fibres should be separated from one another rather than being in a tightly twisted mass or overlapping one another.
3c) Introduce a small drop of mounting medium to the slide.
3d) Gently lay a microscope cover glass over the fibres, so as not to disturb their lacement.
3e) The mounting medium will quickly distribute itself under the cover glass and the sample can then be examined under the microscope.
3f). Look at it under the microscope, starting at low power and working your way up to higher magnification.
3g). Since hair is not a flat object, you probably won't be able to focus on the entire strand at the same time. Adjust your focus to see the outside edges of the strand clearly, and then adjust it again to look at the part in the middle.

4a) Natural fibres will swell slightly as they react to the mounting medium.
4b). Compare different colored hair, if you can. One difference is that dark hair will generally be thicker than lighter hair.
4c) Rough, scaly surface indicates animal fibers. Except silk.
4d) Compare human hair with cat or dog hair.
Strategy 4: Dye Test
One of the oldest methods of identification of fibers is the dye test. There are specific dies that only some types of fabric will take up. In other cases the dyes will look different colors with different types of fibers.
Animal hair
Burn Test observations: (wool, silk, protein based)
1. shrivels away from flame and curls up,
2. burns slowly, self-extinguishes.
3. Smells like burning hair m
4. Very small ashes, dark in color, bead-like mass that breaks apart easily
5. Microscope observation: medulla is more than 1 half of the hair.
1. Wool is the most commonly used animal fiber, it normally is obtained from the soft, hairy covering of sheep and sometimes goats.
2. The fiber is stretchable, easily absorbs water, soft and long lasting, doesn't wrinkle and springs back into shape, and has short fibers.
3. Wool fabric is known for its ability to "breathe" keeping wearers warm in the winter and somewhat cool in warmer weather.
4. Wool picks up static electricity easily when rubbed.
5. Dissolve in bleach.
6. Under the microscope, the wool fiber looks like a long cylinder with distinctive scales on it. The fiber is very curly and springy.

Burn Test: Hard to light, wouldn't stay lit, smells of burning hair. The ashes is very hard, stuck to the fiber sample.
1. Another common animal fiber, was once quite popular, but has been replaced to a great extent by such synthetic fibers as Nylon, Orlon, and Dacron.
2. Silk is made by the mulberry silk worm when spinning its cocoon.
3. Will dissolve in bleach.
4. Under the microscope the silk fiber appears as a thin, long, smooth and shiny cylinder. The fiber is double strands. The fabric is lightweight but can keep its wearer warm

Burn Test: Rapidly burns with uneven flames, smells of burning hair, the ashes are very brittle.
Cat Hair
Cat hair is usually finer than human hair or dog hair.
Dog Hair
Dog hair can be of two different kinds. The outer coat is generally very course and often straight. The undercoat is often fine and can be very curly.
Human hair
1. Round hair tends to be straighter than oblong hair.
Flat hair tends to be kinky.
2. Dark hair is thicker than blond hair and red hair is the finest.
3. But then hair that has been colored artificially can give false clues.
4.Hair is composed of two basic layers.
4a). The inner layer contains the pigment(s). Melanin is the most common pigment in hair.
4b) The amount of melanin determines the color of the hair.
4c) The more pigment, the darker the hair.
4d) Some hair is white. It generally has bubbles in the inner layer.
5. Microscope observation: medulla is less than three quarters of the hair.
Human & Dog hair comparison
1. Bend the hair. Human hair is soft and pliable, while dog hairs are usually firm and tough.

2. Examine the hair using a microscope. Human hair is much thinner than dog hair, cat hair is even thinner than human hair

3. Look at each segment of the hair. Human hair has larger segments than dog hair and presents in a uniform fashion.

4. Magnify the hair so that the roughness between segments is more easily noticed. Human hair is much rougher than dog hair.

5. Examine the hair for differences in pigmentation. Human hair is usually the same color from root to tip, while colors on a dog hair may change several times over the length of the hair.

6. Roll the hair in between your fingers. Human hair is much thinner than dog hair and you should be able to feel a difference between the two.
Vegetable fibers
Burn Test Observations: (cotton and flax, Cellulose based)
1. Does not shrivel away from flame
2. Ignites immediately with contact to flame, burns really quickly and readily in flame.
3. Continues to burn, has an "afterglow" when removed from flame until fibre expended
4. Smells likes burning paper
5. Ashes are fluffy, small, white to grey-coloured
1. Cotton is the most widely used plant fiber, it's the hairs found on the seeds of the cotton plant.
2. The fabric that cotton produces is soft, absorbs water, and wrinkles easily. Cotton is a fabric that is light and cool.
3. The cotton fibers (use a few strands of absorbent cotton) when examined under a microscope will look like a flattened, irregular, twisted ribbon with short fibers.
4. Will Not dissolve in bleach.

Burn Test Observation: A steady orange flame, turns black. smells like burning leaves, ashes is very crumbly, falls apart easily.
The strongest vegetable fiber,, made from the stalk of the flax plant, its two to three times stronger then cotton!. The fiber is long, shiny, and smooth, has poor elasticity, gets softer with use, absorbs water, . and wrinkles easily. Under the microscope it looks like miniature bamboo. Linen gets softer with use and considered a cool fabric for warmer climate.

Point out that linen is often used to make handkerchiefs, tablecloths, napkins, summer clothing and blouses.
This is a plant fiber that is similar to flax (linen) and ramie(but not as fine), therefore it possesses similar properties. Hemp excels in fiber length, strength, durability, absorbency, antimildew and antimicrobial properties. This fiber can be of different qualities, the highest coming from Cannabis Sativa, and lower qualities being Sisal and Manilla Hemp.
Hemp works best in fabrics when mixed with other fibers, although high quality Hemp fabric is produced and wearable, although easily wrinkled.
This fabric also withstands water better then any other textile product and are used to make carpet backing rope, twine and sacks.
Synthetic fibers
Burn Test Observations:
1. Won't light in flames but melts close to the flame.
2. spirals back to stick to the tweezers.
3. Smells of black smoke like burning plastic, slightly sweet.
4. No Ashes, the fibers curl back.

A wide variety of synthetic fibers all have trade
names such as Nylon, Orlon, Dacron, Vinyon, Aralac, Acrilan, Velon, Dynel, Banlon and Lycra. Like rayon, these fibres resemble silk, and under the microscope look like smooth, lustrous, regular shaped cylinders. Synthetic fibers are easily identified because of their uniform thickness (the thickness of natural fibers varies).
Rayon is one of the first successful artificial man-made fibers, although it is not considered synthetic. It is made from cellulose (plant). When manufactured, the rayon fibers resemble silk. This fiber is just as versatile and comfortable as natural fibers, such as cotton.
Under the microscope, the rayon fiber looks like a smooth, lustrous, glass-like cylinder, easily stretchable, doesn't wrinkle, is soft and absorbent and easy to dye, but is not a good insulator. Rayon can be made into cloth that is hard to distinguish from silk, cotton, linen, or wool.

Burn Test: Burned with a steady, rapid orange flame, smells of burning leaves, but no ash present.
ACETATE is a created from wood. Under the microscope there are grooves that run the length of the fibers. Acetate is soft, smooth, and will melt under a hot iron. It does not absorb water. The fabric is cool
NYLON is derived from coal. The fibers under the microscope are smooth and clear rods. Nylon is shiny, tough, stretchable and melts under a hot iron. The fibers are nonabsorbent, quick drying, and doesn't wrinkle. the fabric is cool but clammy.
ACRYLIC is made from petroleum. Under the microscope the fiber is dog-bone shaped with apparent cut ends. The fabric is lightweight, warm, and quick drying.
POLYESTER is derived from petroleum. Under the microscope the rod shaped fiber looks like nylon but is not clear. The fiber does not wrinkle, is silk-like, strong, and absorbent.
Spandex will expand to 54 times its original size
Glass Fiber
1. Glass fibers are made by stretching melted glass into fine filaments, which are spun into thread for weaving into cloth.
2. Lightweight glass fibers are used to make long lasting windows curtains, drapes, and lamp shades. 3. Heavier glass fabrics are used to make fireproof theater and school curtains.
1. Asbestos is the name given to a group of minerals that occur naturally as masses of strong, flexible fibers that can be separated into thin threads and woven to make asbestos cloth.
2. These fibers
are not affected by heat or chemicals and do not conduct electricity.
3. Asbestos cloth was used in fireproof theater curtains and protective suits for use by fire fighters.
4. It was also used as a building material, brake pads and a range of other products.
5. It is now know that the fibers of asbestos are a dangerous irritant. Even exposure to small amounts of asbestos dust can lead to a range of illnesses such as asbestosis, a serious lung inflammation
caused by asbestos exposure, and Mesothelioma a cancer of the chest and abdomen.
DNA pairing
'A' to 'T' and 'C' to 'G'.
1. nucleus DNA and mitochondria DNA
2. The main difference between nucleus DNA and mitochondria DNA is that half of the nucleus DNA came from each parent, but all of the mitochondria DNA comes from the mother. This makes tracing lineage easier through the mother.
3. The hair must have living cells from the root attached to it if regular nucleus DNA tests are to be run, but if mitochondrial DNA is to be tested, there is no such requirement. Therefore any piece of
hair can be tested.
4. Mitochondria DNA testing is the most popular test that is done on hair today in a real crime scene.