Biology detectives: fingerprinting

This activity is part of our Science Lab series. Check out the ANU Science Lab for more experiments! In this activity, join Jack to explore forensic science, latent fingerprint retrieval, and pattern recognition by dusting for prints on glass. Watch the video above to see how it is done.

Fingerprint dusting materials

For this activity you will need:

• A clean glass cup, jar, or smooth surface
• Fine powder (such as cocoa powder, cornflour, or talcum powder)
• A soft brush or small paintbrush
• Clear sticky tape
• Printable results sheet and fingerprint patterns

How to dust for fingerprints: Step-by-step instructions

Step 1: Create a latent fingerprint

1. Press your thumb or index finger firmly onto a clean, smooth glass surface to transfer natural skin oils.
2. Avoid sliding your finger to keep the ridge lines crisp and clear.

Step 2: Dust and reveal the print

1. Dip the very tip of a soft brush into a small amount of the powder.
2. Lightly brush the powder over the area where you touched the glass, being careful not to push down hard so you do not smudge the delicate lines.
3. Gently tap the glass to make any excess powder fall away, leaving behind a clear fingerprint image.

Step 3: Lift and preserve the fingerprint

1. Carefully place a piece of clear sticky tape over the dusted fingerprint.
2. Smooth the tape down gently, then peel it away carefully from the glass surface.
3. Press the tape onto a piece of plain white paper to create a permanent record of the fingerprint for examination and comparison.

Fingerprint dusting: The science explained

• The skin on our fingers features tiny raised friction ridges with sweat pores that continuously secrete natural oils and moisture. Touching a surface leaves behind invisible (latent) oil deposits in the exact shape of your ridge patterns.
• Fine powder particles stick to the sticky oil trails left behind on smooth, non-porous surfaces, making invisible fingerprints clearly visible.
• Every individual has unique fingerprint ridge arrangements, including loops, whorls, and arches, which remain unchanged throughout life.

 & taking it further: Experimenting with variables

• Compare using dark cocoa powder on light glass versus pale cornflour on dark tiles to identify which combination provides the best visual contrast.
• Collect lifted prints from family members and classify them into arches, loops, or whorls to calculate which pattern type is most common in your house.
• Test dusting for fingerprints on different household materials, such as smooth plastic, wood, or textured paper, to determine which surfaces hold latent prints best.

Enjoyed this experiment? Explore more hands-on activities on the Science Lab ANU YouTube channel.