Fingerprints are left on surfaces when you touch them. Gather up fingerprints from different surfaces for an investigative experiment. Sprinkle talcum powder on dark surfaces or cocoa powder on light surfaces. Use an old makeup or paint brush to gently remove any excess. You'll see that the powder sticks to the dirt and oil fingers left behind as fingerprints. Now lay a piece of packing tape carefully over it and lift the powder up in the shape of the fingerprint. Fold the tape, sticky sides together, to preserve the print so you can look at it with a magnifying glass.
Police officers often take the fingerprints of suspects or those they want to rule out as suspects in crimes. Experiment with taking your own and your friend's fingerprints. Color a 2 by 2 inch square with a pencil on copy paper. Press hard enough to color the square in dark. Now, rub across the penciled square, transferring the dark color to the pad of your finger. Next, press the pad of your finger onto a clean piece of white paper, rolling from one side to the other and transferring your fingerprint. You can use a magnifying glass to examine your unique print.
On television, you might see forensic specialists expose fingerprints on objects using glue fumes. Ask an adult to help you try this experiment at home to get the same results. Start by wiping down a smooth-surfaced ink pen, then hold it between your fingers so your fingerprints will be on it. Put the pen inside a wide-mouthed jar. Fold a piece of aluminum foil so its about the size of the jar opening. Put a little puddle of Superglue on the foil and turn the jar, with the pen in it, upside down over the foil. The fumes from the glue will stick to your fingerprints on the pen and expose them.
Gather some of your friends together and play a forensic experiment game. Start by taking everyone's right forefinger print using pencil lead. You'll need two identical prints from each person on separate pieces of paper. Write the name of the person the print belongs to on the front of one set and the back of the other. Now, have everyone examine the clearly labeled prints, then randomly choose a print that's labeled on the back and see if they can match it up.