Forensics Hairs and Fibers

Animal fiber characteristics

Shrivel, do not melt, dissolve in bleach

Vegetable fiber characteristics

Ignite, look charred, but do not melt/shrivel

Synthetic fiber characteristics

Shrivel and melt, fuse together when burned. Look uniform and smooth.

Wool appearance

An animal fiber, cylinder with scales

Cotton appearance

A vegetable fiber twisted, messy strands

Silk appearance

thin, long, smooth cylinders

Linen appearance

smooth, bamboo like structure

Polyester appearance

completely smooth cylinder

Nylon appearance

fine, round, smooth cylinders

Spandex

flattened ridged fibers, clustered, bunches of cynlinders

Wool burn test results

Shrivels, leaving behind a brown-black residue and brittle ash. Smells like burning hair, and self-extinguishes when withdrawn from the flame.

Silk burn test results

Shrivels and leaves a black residue, smells like burning hair or feathers. Leaves behind a crushable black bead.

Cotton burn test results

Burns with a steady flame, smells like burning paper, able to blow flame from a thread like a match, leaves a charred whitish ash

Nylon burn test results

Curls, melts, leaves black residue, smells like burning plastic, ignites only when brought to flame

Linen burn test results

burns at constant rate, no smoke produced, produces sparks, smells like burning grass

Polyester burn test results

Melts, drips when heated, only ignites in flame, bonds to surface it drips on quickly, ash colored

Spandex burn test results

Melts Quickly

Wool

Animal, most common animal fiber, made of keratin

Silk

Animal, smoother than wool, fibroin

Cotton

Vegetable, made of cellulose, most common plant fiber

Linen

Vegetable, made of cellulose of flax, longer fibers than cotton and smoother

Nylon

Synthetic, long fibers

Polyester

Synthetic, fibers of varying length

Spandex

Synthetic, can stretch 8x length, typically blended w nylon or polyester

Medulla

Innermost layer of hair, most fragile, used to identify types of hair.

Cortex

second layer of hair, give hair color and shape, water uptake and nutrients,, has pigment granules w melanin inside, ovoid bodies, cortical fusi

Cuticle

Outermost layer of hair, scaly, protects medulla and cortex, repels water

Human Hair appearance

Little medulla if any, or fragmented/interrupted, scaly imbricated cuticle

Squirrel hair appearance

Thick, latticed medulla

Cow hair appearance

Coarse, thick, ovoid bodies present in cortex, thinner medulla than horse hair, might be fragmented/interrupted

Horse hair appearance

Thick medulla, imbricate cuticle, thick, coarse

bat hair appearance

Strawberries on a stick

Coronal scales

bats, rats, strawberries on a stick

spinuous scales

cats, pointy, spiny

imbricated scales

many mammals, flattened