The uniqueness of human fingerprints was discovered first by Francis Galton in the late 19th century. Galton eventually persuaded Scotland Yard to implement fingerprinting as a means for identifying criminals and investigating crime scenes. Because the oils in our skin combine with dirt to leave prints, certain powders can cling to a print when brushed lightly on them. The amino acids in a fingerprint, too, can react with some household chemicals to create a fingerprint.
- Skill level:
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Things you need
- Plastic packing tape
- Black index cards
- White Index cards
- Cosmetics blush brush
- Talcum powder
- Baby powder
- Baking cocoa powder
- Wood charcoal
- Graphite pencils
- Nail file
- Glass jar
- Super glue
- Several small bowls
- White ceramic canister
- Dark-coloured soda can
- Precision crafting knife
- Sand paper
Take the crafting knife and slice lengthwise down the graphite pencil. Angle the knife blade and slice again about 1/4 inch from the original incision. Pry the wedge of wood out of the pencil to reveal the graphite shaft. You may need to scour the wood a few times to lift the wedge out.
Pry out the graphite shaft and hold it vertically over a small dish. Run the nail file over the graphite horizontally to sand graphite dust onto a small bowl and set aside.
Light a candle and hold a clean glass jar about 4 inches above the candle flame for about three minutes. Wait for soot to form. Flip the jar upside-down so the soot is up and set it aside.
Take the wooden charcoal, or the piece of wood that has been burnt in a wood stove until it is crisp and black, and hold it over a small dish. Rub the sandpaper against it to shake off the black charcoal powder into the dish and set the dish aside.
Place a small handful (about a tablespoon) of each of the following into separate dishes: flour, talcum powder, cornflour, baking cocoa and baby powder. Set these dishes aside.
Press several thumb prints into a dark-coloured soda can and a light-coloured ceramic canister to practice lifting fingerprints. You'll use light-coloured powders on the dark surface, and dark-coloured powders on the light surface.
Brush the first light-coloured powder onto the dark can with the blush brush. When the fingerprint is revealed, take a swatch of packing tape and press it to the fingerprint. Carefully peal the fingerprint from the can using the tape and secure the tape to a black index card for contrast. Set the card in front of the dish of powder you used and repeat this process with different light powders and different prints on the can until you've used them all.
Brush the soot from the jar in a circular motion. Swab the light canister with the sooty brush until a fingerprint appears. Lift and capture the print with packing tape and a white index card. Repeat with powder collected from the graphite pencil and the baking cocoa, placing each fingerprint in front of the substance you used to collect it.
Pour a small, thin puddle of super glue over an area of the soda can where you believe a print to be. Wait about one to two minutes and watch for the super glue to cluster around the amino acids left behind by the lines in your fingerprint.
Tips and warnings
- When you finish collecting fingerprints, look carefully at all the prints you lifted and decide which household products work better than others for your home use.
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