Transcript Fibers and Thread

Fibers and
Threads
Cloth can yield:
class &individual characteristics.
Matching fibers involves comparing:
type of fiber, color, type of dye,production method.
Classification of Fiber
Until 19th C. only natural fibers used to
make clothing
• Mineral – think earth… glass, asbestos
• Animal – silk, wool, fur
• Vegetable (plant) – cotton, linen, hemp
• Synthetic – rayon, nylon, acetate
– Currently 50% all fibers are synthetic
Natural Fibers
Many different natural fibers that come from plants and animals are used in the
production of fabric.
Cotton fibers are the plant fibers most commonly used
in textile materials
The animal fiber most frequently used in the
production of textile materials is wool, and the most
common wool fibers originate from sheep.
http://www.fireflydiapers.com/articles/diaperarticle_naturalfibersabsorb.htm
Synthetic Fibers
More than half of all fibers used in the production of textile
materials are synthetic or man-made.
Nylon, rayon, and polyester are all examples of synthetic
fibers.
Fibers under a microscope
Cross-section of a
man-made fiber
Synthetic Fibers:
Petroleum is the basis for these fibers, and
they have very different characteristics
from other fibers.
Monomers are joined together to form
polymers. The fibers produced are spun
together into yarns.
They have no internal structures, and
under magnification they show regular
diameters.
Comparison of
Natural and
Synthetic Fibers
Visual Diagnostics of Some Common Textile Fibers
under Magnification
QuickTime™ and a
BMP decompressor
are needed to see this picture.
• Fibers can be twisted (spun) into:
any length, thick or thin, loose, or tight.
• A blend can be made to meet different needs
such as resistance to wrinkling.
• Fibers can be woven into fabrics.
– Threads are arranged side by side (the warp).
– More threads (the weft) then are woven back
and forth crosswise in one of a number of
different patterns through the warp.
Weave Patterns
What are some tests that will
help to identify a fiber?
Burn Test
Burning a fiber can give
you hints to the type of
fabric based on what you
see:
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Characteristic odors
Residues
Beading
Smoke or smolder?
• Flame or no flame?
Solvent/Solubility Test
Can the fiber dissolve in certain solvents?
Often the following solvents
are used to help ID a fiber:
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HCl
NaOH
Bleach
Acetone
Dry-Cleaning Solvent
Stain Test
(They show these types of tests in laundry
commercials all the time.)
• Will blood stain the
cloth?
• Will blood ‘bead’ off?
• Is this lipstick?
Microscopic Tests
What can you see using
the microscope?
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Weave
Braids
Folds & Twists
Translucency
Fraying
Was it cut or ripped?
Collection Methods
The two most common ways to collect fiber
evidence are:
#1. The Tape Method… (you probably have done
this before when you have held a critter and they
have left half of their white fur on your black shirt.)
#2. Sweeping/Vacuuming Method: work well but
collects LOTS of other debris.
So… Where else besides clothing
do you look for fibers?
• Rugs
• Drapes
• Couches
• Pillows
• Cars
You can really learn a lot
of stuff from fiber and
other trace material.
Stuff like:
• Skin cells on ropes…
(kidnapping, murder,
suicide?)
• Fibers on duct tape….
(kidnappers’ tool of
choice…)
• Rope characteristics:
# of strands, twist
direction, weave pattern,
color, diameter, weight
• Soil, rocks, debris
give possible location
• Building materials
• Wood & plant material