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FORENSIC 8 | Forensic Chemistry
MODULE 5 | Hair and Textile Fibers
Textile Fibers and Cordage Evidence
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Textile Fibers
In general and broad sense, the word "textile" is derived from the Latin word "textillis" and the French "
textere
", which means "to
weave
".
Yarn
consists of fibers or
filaments
that have been
twisted
together
Textile Production
Textiles begin as
fibers.
Fibers
are made into fabrics.
Fabrics
are made into clothing and other products.
Fiber Evidence
smallest unit of a textile material that has a length many times greater than its diameter
Fibers can be spun with other fibers to form a
yarn
that can be woven or knitted into a
fabric.
Classification of Fibers
Major Classifications:
Natural
Fibers
Natural
/
Man-made
Fibers
Man-Made
Fibers
Non-Technical Test of Textile Fibers:
Feeling test
involves touching and feeling the fabric to know its component fibers
Feeling Test
Wool fabrics will feel
warm
when touched.
Fabric made up of plant fibers such as cotton, linen, and rayon fabrics will feel
cool
to touch.
Non-technical Test for Textile Fibers:
Burning
or
Ignition
Test
preliminary macroscopic examination
determines whether fiber is mineral, animal, or vegetable fiber
destructive
test
Burning or Ignition Test
A single fiber is applied with flame at one end and the following are noted:
Manner
of Burning
Odor
of Fumes
Appearance
of Burnt End
Color
of Ash
Action
of fumes on moistened red and blue litmus paper
Effect
of litmus on a piece of filter paper moistened with
lead acetare.
Ignition Test Result:
Natural Fiber
Ash is soft and odor is of burning hair or paper.
Ignition Test Result
Cellulosic Fibers
Burn rapidly with yellow flame
Afterglow
Soft gray ash
Ignition Test Result
Cotton
ignites on contact with flames
burns quickly
yellowish to orange afterglow
does not melt
odor of burning paper, leaves, or wood
fine, feathery, gray ash
Ignition Test Result
Hemp, Linen, and Ramie yields
the same
results as cotton.
Ignition Test Result
Rayon
Burns slowly without flame
slight melting
soft black ash
Ignition Test Result
Silk
burns slowly, burns itself out
does not melt
shrinks from the flame
black residue
hollow irregular bead, becomes gritty
grayish-black
ash powder
Ignition Test Result
Tencel
yields the same result as Rayon.
Ignition Test Result
Wool
and Other
Protein Fibers
Burns with an orange sputter color
does not melt
shrinks from the flame
strong odor of burning
hair
or
feathers
black residue
hollow irregular bead, becomes gritty
black
ash powder
burns itself out
Ignition Test Result
Synthetic Fiber
both burn and melt
tend to shrink away from the flame
burn with an acrid, chemical, or vinegar-like odor
leaves a plastic bead
Ignition Test Result
Acrylic
Flames and burns rapidly with hot, sputtering flame
black smoke
acrid fishy odor
hard, irregularly-shaped residue
Ignition Test Result
Acetate
flames and burns quickly
odor similar to burning paper and hot vinegar
hard, dark, solid bead residue
Ignition Test Result
Nylon
shrink from the flame
burn slowly giving off black smoke
odor likened to celery
residue: initially a hard, cream-colored bead that becomes darker
Ignition test result
Olefin
/
Polyolefin
chemical type odor
hard, tan-colored bead
flames create black smoke
Ignition test result
Polyester
shrink from the flame giving off black smoke
somewhat sweet chemical odor
residue: hard, cream-colored bead that becomes darker tan
Ignition Test Result
Spandex
burns and melt
does not shrink from the flame
chemical type odor
residue: soft sticky black ash
Technical Test for Textile Fibers
Microscopic
Test
Fluorescent
Test
Chemical
Test
Microscopic Test of Natural Fibers
Cotton
single elongated cell
flat, spirally twisted ribbon-like tube with granular surface
Mercerized Cotton
- no natural twist, swollen, straight, smooth and rounded with a shining surface
Microscopic Test of Natural Fibers
Linen
having multiple sided cylindrical filaments with fine pointed edges
filaments show nodes at intervals
looks like a bamboo stick having joints that result into a little unevenness
Microscopic Test of Natural Fibers
Wool
irregular, roughly cylindrical, multi-cellular structure with tapered ends
Three Basic Layers of Wool
Epidermis
- outer layer
Cortex
- middle layer
Medulla
- inner layer
Note:
Medulla
is seen only in coarse and medium wool fibers under highly powerful microscope.
Microscopic Test of Natural Fibers
Silk
Fine and Lustrous filaments are shown clearly looking like a transparent rods with triangular shape
Elliptical shape
Wild silk
/Tussah fiber - flattened, coarse, thick, and broader fiber having fine wavy lines all across its surface
Microscopic Test of
Manmade
Fibers
These fibers are difficult to identify through microscope because of similar appearance of many fibers.
Microscopic Test of Natural Fibers
Rayon
uniform diameter with glass-like shine
if delustered, fiber shows marks similar to
pepper
viscose
fiber looks irregular
Microscopic Test of Manmade Fibers
Acetate
lesser irregular than viscose fiber of rayon
has indentations that look like occasional marks when viewed longitudinally
Microscopic Test of Manmade Fibers
Nylon
generally appears fine, round, smooth, and translucent
shiny appearance
Microscopic Test of Manmade Fibers
Aramid
looks smooth and straight
may be round like a peanut's shape
Microscopic Test of Manmade Fibers
Polyester
smooth, straight, round
changes in context of texture and luster due to finishing processes
Microscopic Test of Manmade Fibers
Spandex
appearing like groups of fibers fused together
Lycra fiber
- fused multifilament
individual fibers are dotted and in shape like that of a dog-bone
straight when viewed longitudinally
Microscopic Test of Manmade Fibers
Polypropylene
looks somewhat round (cross sectional)
looks straight and smooth (longitudinally)
Microscopic Test of Manmade Fibers
Glass
looks smooth, round, translucent, shiny, and flexible
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