Dermatoglyphics for Brownies

Dermatoglyphics (Forensic Fingerprints)

Materials

Pick Up Kit

  • 2 Sheets of white paper
  • Transparent tape (scotch tape)
  • Magnifying glass
  • Pencil
  • Unsweetened cocoa powder
  • Paintbrush

Home Materials

  • Clear glass or jar

What to Do

  1. On one sheet of paper, trace your hand with a pencil.
  2. On the other piece of paper, scribble hard with the pencil until a small area is covered with the graphite from the pencil lead.
  3. Rub your pinkie around in the graphite until it is covered with gray.
  4. Carefully place your graphite-covered pinkie finger on the sticky side of a piece of transparent tape and gently lift your finger off the tape. A clear finger print should be visible.
  5. Place the tape facedown on the pinkie finger of the hand you traced.
  6. Repeat steps 3-5 with each finger until you have finger prints on each of the fingers you traced.
  7. Inspect the fingerprints under a magnifying glass.
  8. Rub your hands together to spread the oil on your skin around, then make several fingerprints on the clear glass.
  9. Using a brush, gently dust some cocoa powder onto one of those fingerprints on the glass.
  10. Blow the excess cocoa powder away and lift the fingerprint with a piece of tape.
  11. Tape the fingerprint onto a piece of white paper and try to match it to one from your hand. Can you figure out which finger it came from?

What to Talk About

  • Skin’s outer layer is called the epidermis, and a fingerprint is the impression left by epidermal ridges on human fingers. These ridges help us feel things and grip things better.
  • No two people have identical fingerprints, but patterns can run in families. Let’s wonder if the people in our families might have fingerprints that are similar to ours.
  • These patterns tend to look like whorls, loops or arches, and fingers often leave imprints of sweat, oil, ink or other substances behind.
  • Fingerprints are often essential tools in crime scene investigations.
  • It might be neat to collect water glasses from the table after a meal. Do you think you might be able to identify who used each glass?
  • I wonder if we could do this same activity using cornstarch and black paper and how it might compare to the graphite.

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