======Iodine Vapor Fingerprints======


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**Alternative titles:** Revealing Fingerprints with Iodine Fuming
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====Summary====                   
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====Procedure====  
  - Place a sheet of paper with a fingerprint inside a sealable container such as a jar or plastic box.  
  - Add a few solid iodine crystals to the bottom of the container (do not let them touch the paper).  
  - Seal the container and wait a few minutes for iodine vapors to fill the space.  
  - Observe the fingerprint as it gradually appears brown where iodine binds to the oils.  
  - Remove the paper when the fingerprint is clear.



====Links==== 
The Home Scientist 006 - Forensic Fingerprinting I: Iodine Fuming: 
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Fingerprint Fixing with Iodine - RACInational: 
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📄 Iodine fingerprint - MEL Science (uses copper sulfate and potassium iodide instead of solid iodine): [[https://melscience.com/AU-en/chemistry/experiments/diffusion-iodine-fingers/?srsltid=AfmBOopdRexxLJsB66vaYzwTo4NRhco_DSCZ05F8UynAJFxTpqRPYMWn]]\\



====Variations====
  * Try developing fingerprints on different porous surfaces such as cardboard or fabric.  
  * Place the container on a warm (not hot) surface to increase sublimation and speed up fingerprint development.  
  * Use starch solution after iodine development; the starch-iodine complex produces a dark blue color, making the fingerprint more visible.



====Safety Precautions====
  * Wear safety goggles and protective gloves.  
  * Handle iodine crystals with care; avoid direct skin contact.  
  * Perform the experiment in a well-ventilated area or under a fume hood to avoid inhaling vapors.  
  * Keep iodine crystals sealed when not in use, as vapors can irritate eyes and lungs.  
  * Dispose of iodine residues safely according to local chemical disposal rules.




====Questions to Consider====
  * Why does iodine make the fingerprint visible? (Because iodine vapors bind to fats and oils present in fingerprints.)  
  * Why does heating the iodine speed up the fingerprint appearance? (Heating increases sublimation, releasing vapors faster.)  
  * Why do the fingerprints fade over time? (Iodine sublimes back into the air, leaving less bound to the fingerprint.)  
  * What is the advantage of using iodine fuming over ink or powder methods? (It works well on porous surfaces like paper where powders are less effective.)