======Forensic Fiber Analysis======


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**Alternative titles:** Crime Scene Fiber Testing
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====Summary====                   
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====Procedure====  
  - Collect a small sample of fiber evidence.  
  - Conduct a burn test: observe whether the fiber burns quickly or shrinks from the flame, note the smell, smoke color, and residue (cotton leaves soft ash, polyester leaves a hard bead).  
  - Alternatively, use a polarized light microscope:  
    - Examine the fiber’s refractive index to see how it bends light.  
    - Observe the fiber’s colors under polarized light.  
    - Study the fiber’s shape, texture, and condition (e.g., silk is smoother than wool; worn fibers look different from new ones).  
  - Record results to determine fiber type and possible origin.



====Links==== 
What is Forensic Textile? Forensic Textile Analysis - Textile Vlog: 
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📄 Chemistry Cracks the Case: Focus on Fiber - ACS: [[https://www.acs.org/education/celebrating-chemistry-editions/2022-ncw/chemistry-cracks-the-case-focus-on-fiber.html]]\\


====Variations====
  * Compare fibers from different fabrics such as cotton, wool, silk, and polyester.  
  * Test blends of natural and synthetic fibers.  
  * Use both burn and microscope tests to cross-check results.



====Safety Precautions====
  * Conduct burn tests in a well-ventilated area to avoid inhaling harmful fumes.  
  * Use heat-resistant tools such as tongs or tweezers when handling burning fibers.  
  * Perform microscope tests first if preserving the sample is important.  
  * Always follow classroom fire safety procedures.




====Questions to Consider====
  * Why does cotton smell like burning paper? (Both are made of cellulose, so they produce similar combustion products.)  
  * Why do forensic scientists prefer using polarized light microscopy instead of burn tests? (It preserves evidence and gives more detailed information without destroying the sample.)  
  * Can fiber analysis alone identify a specific suspect? (No, it can only narrow down or exclude groups of people; DNA or fingerprints are needed for exact matches.)  
  * How might coatings or treatments on fabric affect burn test results? (They can change how the fiber burns, leading to possible errors.)