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Everyone loves a good mystery! Well, okay, not everyone, but lots of people. One of the hallmarks of a mystery, or any criminal investigation, is fingerprinting. Police officers and detectives have been looking for fingerprints to identify suspects for over 100 years. Today you’ll examine your fingerprints and see where you can find some around your house. It’ll be fun…but it’ll also be messy. I hope you don’t mind cleaning up a bit!
Materials:
- Clear tape (packing tape or transparent Scotch tape)
- Baby powder or powdered sugar or flour
- A small bowl
- A clean makeup brush
- Dark colored construction paper
- A magnifying glass (optional)
Process:
- First, examine your fingers. Use a magnifying glass if you have one. See the different patterns on your fingers? That’s what we’re going to be looking around your house for.
- Brainstorm some places that might have lots of fingerprints. What are some places or things that get touched a lot? Doorknobs? Cups and glasses? Silverware? Lightswitches?
- Once you have a few places you’d like to search for fingerprints, pour some of your powder (baby powder is best, but the other two work as well) into your bowl.
- Dip your makeup brush in your powder. Use the brush to lightly dust the areas you’re checking for fingerprints. Don’t brush too hard because you might rub the prints away.
- When you’ve dusted all the places you want to dust, it’s time for your clear tape. Place the sticky side down on your powdered places and then gently peel it back up. If all goes well, you’ll get some fingerprints in the powder from at least some of your places.
- Put the tape on your construction paper. This will make the white powder easier to see against the dark background. Examine the prints on the tape and compare them to yours and your family’s. Can you tell whose prints are on what? If you have a magnifying glass, it can help you identify the prints!
Summary
Every human being in the world has fingerprints, and everyone’s are unique. The technical term for fingerprints is “friction ridges,” and humans aren’t the only ones who have them. All primates, (apes, monkeys, and other animals like that) also have fingerprints. All of us can leave fingerprints on surfaces we touch thanks to sweat, oil, grease, or things like ink or paint that get on our fingers. When you dusted, the dust stuck to those patterns left over from someone touching something and then you picked them up with your tape.
Since everyone’s prints are different, fingerprints are an excellent way of identifying who somebody is. This is why they’re so useful for detectives. If someone broke into a store and stole money out of the cash register, detectives can dust for prints. Then they can see which ones match the people who work at the store and which don’t. If they find some prints they can’t match to the staff at the store they know they might have the prints of the thief. All they have to do is go through their database of prints, which is just a big computerized collection, and try to match them to a known suspect.
There are three main patterns of prints:
Loops
Whorls
Arches
You probably have a combination of them on your hands, and even those same patterns look different on different people. Loops are most common, whorls come in second, and arches are a distant third. Only 5% of fingerprints in the world have arches. Which patterns can you identify on your hands?
Want more Saturday Science? See all of our at-home activities on the blog or Pinterest.
