Unit 6 - Fibers

Question 1

Can fiber evidence have probative value?

Answer 1

Yes

Question 2

Characteristics of synthetic fibers

Answer 2

Uniform and regular shape of cross section
Stronger
More chemically inert

Question 3

Can a piece of fabric be individualized to a particular garment?

Answer 3

Yes, but only if the piece fits a tear or rip in the garment.

Question 4

Can a fiber be individualized to a particular garment?

Answer 4

No. Fibers are class evidence.

Question 5

Difference between a fabric and a fiber

Answer 5

Fabric - made from fibers

Fibers - made of twisted elements that are either natural or artificial.

Question 6

Is silk synthetic or natural?

Answer 6

Natural

Question 7

Most common type of natural fiber

Answer 7

Cotton

Question 8

Most common type of synthetic fiber

Answer 8

Nylon

Question 9

Can an investigator use the way a fabric accepts a specific dye to identify and compare samples?

Answer 9

Yes

Question 10

Optical microscopy

Answer 10

The most important method of fiber identification

Involves polarizing light and comparison microscopes

Question 11

Electropherogram

Answer 11

Plot of results from an analysis done by electrophoresis

Question 12

Natural fibers

Answer 12

Cotton
Wool
Linen
Silk
Cashmere
Jute

Question 13

Synthetic Fibers

Answer 13

Nylon
Polyester
Acrylic
Plastic
Rayon
Acetate
Dacron

Question 14

Polymer

Answer 14

A molecule consisting of many repeating units. Can be naturally occurring or synthetic.

Question 15

Are all fibers polymers?

Answer 15

Yes

Question 16

What types of tests can be used to test the dye in a particular fiber?

Answer 16

Chemical tests or chromotography

Question 17

Is linen natural or synthetic?

Answer 17

natural

Question 18

For there to be an association between a questioned fiber and an unknown fiber, what percentage of tests you run on the two samples must have identical results?

Answer 18

100% One off means the two fibers cannot be associated.

Question 19

What was the first truly synthetic fiber to be discovered and sold?

Answer 19

Nylon

Question 20

What fiber will fluoresce under ultraviolet light?

Answer 20

Cotton

Question 21

The Amanda Davies case showed the importance of what?

Answer 21

fiber transfer

Question 22

First person convicted on the basis of fiber evidence

Answer 22

Wayne Williams

Question 23

Tests that can be done in lab to analyze fibers (in addition to what we did in class)

Answer 23

refractive index,
any type of chromotography,
optical microscopy
any infrared study

Question 24

Properties that should be examined when comparing two fibers

Answer 24

birefringence
diameter
color
cross-section
fluorescence

Question 25

Fibers that come from plant sources

Answer 25

Linen | Cotton

Question 26

Fibers that come from animal sources

Answer 26

Asbestos | Mineral wool

Question 27

Difference between a synthetic fiber and a natural fiber

Answer 27

synthetic fibers - man made through chemical alteration of natural fibers natural fibers - produced by plants or animals

Question 28

What does wool smell like when it is burned?

Answer 28

burning hair

Question 29

Becke line

Answer 29

a light colored halo that appears around an object when it is immersed in a liquid of a different refractive index

Question 30

Blend

Answer 30

a fabric composed of two or more different types of fiber, usually as warp and weft

Question 31

Chromatography

Answer 31

a method of separating components of mixtures based on preferential absorption or partitioning of components in a gas, liquid, or solution

Question 32

Chromatogram

Answer 32

the record of chromatographic separation

Question 33

Density

Answer 33

a physical property of matter | D = M/V

Question 34

Elute

Answer 34

in chromatography, to extract one material from another, usually by means of a solvent

Question 35

Filament

Answer 35

single strands of material, usually twisted or bonded together to form a thread or yarn

Question 36

Fluorescence

Answer 36

the absorption of light at one wavelength and its remission at a longer wavelength

Question 37

Plain

Answer 37

simplest and most common weave. The warp and weft yarns pass under each other alternating

Question 38

Twill

Answer 38

the warp yarn is passed over one to three weft yarns before going under one. Makes a diagonal weave pattern

Question 39

Satin

Answer 39

yarn lacing is not uniform. Creates long floats | Interlacing weaves pass over four or more yarns.

Question 40

Viscosity

Answer 40

the resistance of fluid to flow

Question 41

Warp

Answer 41

the lengthwise yard or thread in a weave

Question 42

Weft

Answer 42

the crosswise yarn or thread in a weave; also called the woof.

Question 43

Yarn

Answer 43

a continuous strand of fibers or filaments, either twisted or not