In class we performed a fabric lab. This lab was done to see which fabrics were synthetic and which were natural. We used methods that would be similar to those that would help identify fabrics found at crime scene. The tests and observations were for water retention, flammability, reactions to chemicals, weave pattern, and filament number. Our lab concluded that the natural fabrics were cotton and wool. The synthetic fibers were nylon, polyester, and rayon. The natural fabrics tended to have too many filaments to count, while the synthetic fabrics had filaments that could be counted. I think that the filament number could help identify fabrics to a certain point. They can be useful for determining whether a fabric is natural or synthetic, but they cannot determine the exact fabric based on the number of filaments. The nylon and rayon were both knitted. The wool had a satin weave pattern and the polyester had a plain weave pattern. The cotton had no distinct pattern. The synthetic fabrics were mostly knitted. The float patterns can determine the way threads line up, which determines the weave pattern of a fabric. Each fabric has a certain weave pattern that is used and that can be identified by using the float pattern. The flame test was performed and the natural fabrics generally burned while the synthetic fabrics melted. The water retention test had mixed results, but natural fabrics usually held more water while the synthetic fabrics did not. The synthetic fabrics were created specifically to not hold in water so they could dry quicker. It was important to let each fabric dry for an equal amount of time because the different amounts of time could vary the results.
Based on the observations from the chemical tests, this test does not to seem to be useful for identifying fabrics. Each chemical had a similar effect on each fabric and there was not much of pattern for which fabrics were natural or synthetic.
I learned from this lab that different fabrics have different weave patterns which are determined by their float patterns. I did not know that the number of filaments can help determine the type of fabric being analyzed. I knew that some fabrics melted or burned but I did not know why this happened, but now I know this happens because of the type of fabric is it.
Doing this lab and learning about fabrics has taught me how forensic scientists test fabrics found at crime scenes. Flame tests can be done to determine whether a fabric is natural or synthetic. Analyzing the weave pattern can help determine the type of fabric. Every type of fabric has a certain set of characteristics that can be used to match an unknown fabric.