fibers and threads. cloth can yield: class &individual characteristics. matching fibers involves...
TRANSCRIPT
Cloth can yield:class &individual characteristics.
Matching fibers involves comparing:type of fiber, color, type of dye,production method.
Classification of FiberClassification of FiberUntil 19th C. only natural fibers used tomake 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
Many different natural fibers that come from plants and animals are used in the production of fabric.
http://www.fireflydiapers.com/articles/diaperarticle_naturalfibersabsorb.htm
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.
Natural 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.
Cross-section of a man-made fiber
Synthetic Fibers
Fibers under a microscope
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
• 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.
Burn Test Burning a fiber can give you hints to the type of fabric based on what you see:
• 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:
• 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?
• 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.
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