Chemical Fingerprinting

Did you know that the patterns on the tips of your fingers are unique? It’s true! Just like no two snowflakes are alike, no two people have the same set of fingerprints. In this experiment, you will be using a chemical reaction to generate your own set of blood-red prints.

Here’s what you need

  • 1 oz. bottle of baking soda or sodium carbonate (washing soda)
  • water
  • 1 sheet of goldenrod paper (make your own here!)
  • 1 paper towel
  • 1 magnifying lens



Here’s what you do

  1. Pour a couple teaspoons of the baking soda (sodium carbonate) into a cup of water. Swish your right index finger in the damp baking soda and then roll that finger on the goldenrod paper. This should leave a bright red fingerprint on the paper. Label it right index.
  2. Continue the procedure for each finger on both hands to make a full set of prints. Be sure to label each fingerprint as you make it to identify which print goes to each finger. Don’t forget to make prints of your thumbs!
  3. Compare your prints to the basic patterns in the guide. Check for features such as whorls or loops and label them appropriately on your prints. Use abbreviations such as A for accidental, PW for plain whorl, and DL for double loop.
  4. After you have identified the dominant pattern on each of your fingertips, prepare a simple chart for each hand to record the data by finger.
  5. When you are finished studying your own prints, ask a volunteer to let you make prints of their fingers.

What’s going on?

Goldenrod paper is made using phenolphthalein, a chemical that turns red when exposed to materials with relatively high pH. Baking soda (or sodium bicarbonate) is a base which has a pH of about 8.5. Rolling your baking soda covered fingers on the goldenrod paper creates a chemical reaction which produces a red fingerprint.



  1. What are the three main types of patterns on fingerprints? Describe each.
  2. How do fingerprints have the potential to help solve crime?
  3. Why does baking soda (or washing soda) show up red on the paper?
  4. What kind of pH do bases have?
  5. What kind of reaction do we see when the red fingerprints show up on the paper?