- Procedure:
Collect a fiber from the "crime scene " by carefully lifting the fiber with a pair of forceps. Do not touch the fiber with your hands. Place the fiber on a piece of white paper, then fold the paper in half twice.
- Carry the fiber to your lab station. Prepare a wet-mount slide of the fiber by placing it on the slide, adding a drop of water, and covering the fiber and water with a cover slip.
- Examine the fiber under low, medium and high magnification of your microscope. Sketch what you see. Note any pits or striations on the fiber. Place the sketch and notes in your data table.
- Compare "crime scene fiber" to the samples taken from the suspects. Sketch each of these samples at medium power. Place your sketch and notes about the fibers in your data table.
- Light your candle and follow the following directions with the crime scene fiber to the known samples. Record your observations in the data table.
a Holding the fiber in the forceps, bring it close to, but not touching, a flame. Describe the fiber's behavior as it approaches a flame: does it begin to melt, ignite, or curl?
b Holding the fiber in forceps, touch the fiber to a flame. Does it ignite quickly or slowly? Does it sputter, drip, or melt?
c Remove the fiber from the flame and describe how it behaves. Does it self-extinguish, continue to burn, or continue to glow?
d Note any odor associated with the fiber in the flame. Does it smell like vinegar or hair?
e What kind of residue is left after the fiber is removed from the flame? Does the fiber leave a white, fluffy ash, a hard bead, or a melted blob?
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