STEM+ Camp 2014
CSI: Who Stole the Robot?
Forensics of Fibers
Fibers are the smallest component of textile materials. You encounter a variety of fibers each day.
Fibers make up thousands of products, including clothing, upholstery, carpet, rope, and building materials. As
you interact with these products, loose fibers become attached to your body and clothes. When you enter a
room, you pick up some of the fibers present in the room. You also drop some of the fibers you are carrying.
Therefore, fiber evidence can often provide information about where people have been. In most cases, fibers
are analyzed based on their physical and chemical properties. You will perform a burn and dye test to help
identify the fibers found at the crime scene.
Burn Test
When held near a flame different fibers will exhibit different behaviors. Some will begin to melt and
others will twist or curl up. When ignited they will also react differently. Certain fibers burn slowly, while
others burn quickly. Some will melt and drop off before the flame reaches the rest of the fiber. If the fiber
melts, it is likely a synthetic material such as nylon or polyester. Odor is also a powerful tool in identifying an
unknown burnt fiber. If the smell is similar to that of burning hair, the fiber is most likely silk or wool. If the
smell is similar to burning paper or wood, the fiber is probably cotton, rayon or linen
Data Table
Fabric Type
Wool
Acrylic
Polyester
Nylon
Cotton
Acetate
Observations When Heated
Observations When Ignited
Dye Test
Fabrics are also identified based on how chemical dyes bond to them. How well a dye is attracted to a
piece of cloth (its affinity) depends on both the fabric and the dye. Dyes are water-soluble compounds. In
general, dyes have a greater affinity for natural fibers like wool and cotton. Many synthetic fibers, such as
acrylic and polyester are hydrophobic (water-fearing) so they are more difficult to dye.
Fabric Type
Wool
Acrylic
Polyester
Nylon
Cotton
Acetate
Color
Crime Scene Fiber
- Burn Test
Fabric Type
Crime
Scene
Fiber
Observations When Heated
Observations When Ignited
- Dye Test
Fabric Type
Crime
Scene
Fiber
Color
- Conclusions: What type of fiber/cloth do you think was found at the crime scene?
Please use at least two pieces of data to support your conclusion.