Finger prints come in three varieties: plastic, visible and latent. Plastic and visible are easy enough to see because they’re left on soft surfaces like dust, or colored surfaces like blood smears and wet paint. Latent prints are difficult to see because they’re left on nonabsorbent surfaces like wood and glass. One way to make those latent prints appear is to treat them with Super Glue. It’s the cyanoacrylate ester in the Super Glue fumes that chemically reacts to the latent prints, making them visible to the naked eye.
Install your heat source in the box. If you're using a coffee cup warmer as a heat source, set it in the corner of the box and cut a very small hole for the electrical cord to run through. If you're using a 60-watt light bulb, place it at one end with a small hole for the threads of the bulb and the electrical cord to fit outside the box.
Lean item with latent prints against an interior wall of the box, away from the heating element.
Make a small cup using crumpled aluminum foil and squeeze about a nickle size of liquid Super Glue into it. The cup you've created from crumpled foil will serve as a heating dish for the Super Glue. Place the aluminum foil cup on top of the coffee warmer or light bulb so that it can be heated.
Place a coffee mug of hot water into the box to create humidity. The heating element should be on one side, the item with latent prints in the center and the mug on the other side. The item you are lifting prints from will between the heating element and mug of hot water.
Attach the lid securely to the box. The tighter the box is sealed, the better the fuming chamber can do its job of lifting prints.
Plug in the coffee warmer or light bulb and allow it to heat for 10 minutes.
After 10 minutes, open the fuming chamber and check your prints. If they didn't show up white enough, add a little more liquid Super Glue to the small aluminum foil cup, replace the mug of hot water with a fresh cup of hot water and let it heat for 10 more minutes. This reheating should make the latent fingerprints stand out more clearly.
Take care with both the heat source and Super Glue. Left on for too long, the coffee warmer and light bulb can both cause injury or fire. Super Glue reacts with itself, so don't use it in a box in which you have already run the experiment. You'll need a fresh box each time. Generally, one 10 minute session will give you the best results. By the time you see deep white ridges on the latent fingerprints, you have over-processed them. Use Super Glue sparingly.
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