Eyes will light up with this glow-in-the-dark forensics activity
Discovery Place Science
Forensic science includes the preservation and reconstruction of evidence after time has passed. It can be both challenging and fun, and is a great model for scientific thinking.
In order to solve crimes, one must find clues, draw a hypothesis (or theory), collect data, connect the dots and come to a conclusion. One of the oldest techniques in this discipline of science is fingerprinting.
Every person has a unique set of fingerprints. Of the billions of people walking around this earth, no two people have the same fingerprints! We get our unique fingerprints from a combination of three patterns. The basic patterns formed under the skin of our fingertips are arches, loops and whorls.
Collecting fingerprints has been a method of the Federal Bureau of Investigation since the 1920s. Fingerprints left behind by suspects help Crime Scene Investigators identify individuals of interest in a case.
There are several methods to lift fingerprints. In recent years, there have been advances in how police and investigators dust for prints at a crime scene.
Australian scientist Dr. Kang Liang sought to help police officers improve the way they dust for prints by creating ways to make them glow using fluorescent light. Fluorescence is given off by certain substances when they absorb the light. First the substance absorbs the energy, then it emits light. When the light source is removed, the fluorescence stops.
This activity will allow us to simulate Dr. Liang’s techniques using household products like turmeric and petroleum jelly. Don’t have a black light? Don’t worry! We can make our own.
Here’s how to make a DIY cellphone black light. If you have a black light at home, you can skip this part.
- Cell phone
- Clear tape
- Blue Sharpie
- Purple Sharpie
- Yellow highlighter
- White printer paper
1. Put a strip of clear tape over the flashlight of your phone and color it with blue Sharpie so the entire lens of the flashlight is covered.
2. Put a second strip of clear tape over the first layer of colored tape on the flashlight of your phone and color the second layer of tape with the blue Sharpie.
3. Add a third layer of clear tape over the other layers and color this layer with the purple Sharpie.
4. Write a message on the white piece of paper with a yellow highlighter.
5. Turn off the lights! Turn on your phone flashlight and shine it over the written highlighter. It should glow like the image below!
Now that we have our black light ready, we can move on to dusting finger prints! Here’s what you will need:
- Glass cup or jar
- Small, soft-bristle brush
- Clear tape
- Petroleum Jelly
1. Apply a very thin layer of petroleum jelly to one of your fingertips. Be sure to clean off excess petroleum jelly for a clean print.
2. Press your fingertip to a clean glass. If needed, have an adult assist you with this.
3. Use turmeric to coat the fingerprint.
4. Carefully brush the excess turmeric away with a soft bristle brush. You should end up with a fingerprint that looks close to this:
5. Turn off the lights and shine your blacklight flashlight onto your newly dusted fingerprint.