Detective Science: Fingerprinting

Use a pencil and some clear tape to make fingerprints! This is such a fun detective science activity because the fingerprints come out so clear and detailed.

I did this activity with the older boys when they were younger, but we haven’t tried it in a long time. The younger three kids have been interested in spies lately, so we tried this classic fingerprint experiment.

This fingerprinting activity is even more fun if you have a decent magnifying glass. I got a nice one at Michael’s craft store in the sewing department. Use one of their 40% off coupons, and it’s a good deal!

Supplies Needed:

• Paper or index cards
• Pencils
• Scotch tape or similar tape
• A magnifying glass – optional

First, use a pencil to scribble an area of dark graphite. This is going to be your “stamp pad,” so make it nice and big. And plenty dark.

Then rub your finger in the pencil graphite. Make sure to get the sides of your finger. You kind of have to roll your finger around to get enough coverage to have a good fingerprint.

Now stick a piece of tape to your finger. The sticky side of the tape will pick up the fingerprint.

Stick the tape onto a piece of white paper. We found that large index cards were the perfect size for each person to make prints for multiple fingers. It’s fun to compare your fingers to your thumb!

It’s amazing how much detail each fingerprint has! We had fun examining them with the magnifying glass and looking for the three main fingerprint patterns: arches, loops, and whorls.

The Science of Fingerprints

Is it true that no two fingerprints are the same? The truth is that this has never been proven! Fingerprints from a crime scene are linked to a particular person by finding a certain number of points of commonality, and interestingly enough, not everyone agrees on how many points should match in order to prove the identity of a person. It’s an interesting topic!

However, even though it hasn’t been proven that no two people have the same fingerprint, the odds of having the exact same fingerprints as another person is estimated to be about 1 in 64 billion (source).

Here’s an interesting article from Smithsonian Magazine that talks about the history of fingerprinting.

And here’s an article about the three basic fingerprint patterns.