Key concepts
Forensic science
Chemistry
Biology

Introduction
Practise you know that y'all get out fingerprints on everything yous bear upon? If your hands are very dirty, this is obvious because you can actually see them. But even if your hands seem clean, your fingerprints will stay behind on the surfaces y'all touch—they are simply invisible! Practise you want proof? Then make them visible in this activity and collect your ain fingerprints!

Background
Detecting invisible fingerprints is an of import chore in forensic science, a branch of scientific discipline that helps criminal investigations by collecting and analyzing evidence from law-breaking scenes. Each fingerprint pattern is unique to a specific person, and therefore a very reliable fashion of identifying a suspect. At that place are different types of fingerprints that can be left behind: an imprint in a soft surface, such as wax or soap; a patent fingerprint, visible to the naked eye, such every bit those resulting from muddied hands; and latent fingerprints, which are invisible.

These invisible latent fingerprints are made of water, fatty acids, amino acids and triglycerides—in other words, they result from the oil and sweat that your peel produces naturally. To make them visible, you lot take to find a way to notice one of these substances nowadays in the invisible fingerprint. The easiest method is called dusting, in which you apply a very fine powder that tin can stick to the oil in the fingerprint. Once the fingerprint becomes visible, you can lift information technology from the surface with clear tape and transfer information technology to another surface to and so take into the laboratory to analyze further. Other methods include using chemicals that react with the amino acids or water in the fingerprint; the chemical reaction results in a colored fingerprint, which you can and then analyze easily.

Many factors determine the quality of a fingerprint on a surface. One of the most important factors is the surface texture. Fingerprints are about easily detected on smooth, nontextured dry surfaces. The rougher or more porous the textile the more difficult it will be to go good fingerprint evidence. Another factor is the skin condition of your fingertips. If they are very sweaty and oily, you lot are more than probable to get out backside prints than if they are dry and clean. Test it yourself, and collect your own fingerprint evidence like a real crime scene investigator in this activeness!


Materials

  • A glass or polish metallic surface (where y'all have permission to test for finger prints!)
  • Raw cacao pulverisation if your test surface is light; baby powder if information technology is dark
  • White newspaper if your test surface is light; black paper if it is night
  • A small bowl
  • Articulate record
  • A fine brush with soft bristles, such as a makeup castor
  • Dust textile
  • Water
  • Soap
  • Paw lotion


Preparation

  • Pour a little of the cacao or baby powder into a small bowl.
  • Wipe the smooth glass or metal surface that y'all are using for your experiment very thoroughly with the dust textile.


Procedure

  • Cull one finger of one of your easily and printing information technology firmly onto the clean, smooth surface. Retrieve where yous put it on the surface. Tin can yous see your fingerprint?
  • Dip your castor carefully into the cacao or baby powder. (If your fingerprint is on a dark surface, use the baby pulverization; if on a calorie-free i, cacao.) Only the tips of the bristles should be covered with pulverization. Then, tap the castor to remove any excess powder.
  • Gently sweep the castor carefully over the area where you put your fingerprint. Make sure to not apply likewise much pressure so that you do non wipe the impress away. If necessary, add together more powder to the brush, but be conscientious not to add too much. What happens when you use the powder to the surface? Can you lot meet a fingerprint developing?
  • When you lot are done, gently blow off excess powder from the surface and check your result. Did you lot become a visible fingerprint? How well can y'all see the impress? Can y'all make out the fingerprint pattern?
  • Use a slice of clear tape and carefully press the record down onto the surface on superlative of the developed fingerprint. Peel the record off and transfer the fingerprint onto a piece of paper. (If you used night cacao, utilise white newspaper; for babe powder, use black.) Did you lot successfully transfer your fingerprint? Does it withal look the aforementioned on the newspaper compared with your drinking glass or metal surface?
  • Wash your hands thoroughly with warm water and soap. And then, echo the steps with the same finger you chose before. Did yous get a fingerprint over again? How does it look compared with the outset one? Can you still see lots of details?
  • Finally, apply some hand balm and repeat the fingerprint steps once more. How does this fingerprint compare with the previous ones? Is it easier or more difficult to discover?
  • Once y'all have transferred all your fingerprints onto a slice of paper, compare your results. Practice they all expect the aforementioned? Which one can you see the best, the to the lowest degree? Tin can you explain your results?
  • Actress: In this activity you tested a overnice, smooth glass or metal surface. Exercise you call up other surface textures or materials will result in fingerprints equally well? At that place is only one way to find out! Exam other materials such as paper, textiles or woods. How do fingerprints look on these surfaces?
  • Extra: Now that yous are like a professional in collecting fingerprints from surfaces, endeavor to notice them in your business firm! Where is the best place to look for them? Tin can you find your ain or some from your family members and make them visible? Be certain y'all have permission to dust on surfaces before y'all test them.


Observations and results
Were you able to collect some of your ain fingerprints? On a shine surface such as drinking glass or metallic, fingerprints tend to stick very well. With your unwashed hands, you should have been able to brand your fingerprint visible with either cacao or baby powder. Only a little powder applied with a brush should exist enough to reveal your fingerprint. If yous apply also much powder, however, the fine details of your print might have gotten lost. When you printing too hard onto the surface with the castor, the fingerprint will be wiped abroad—so yous have to be careful when treating the surface with the powder.

Your freshly washed hands accept much less pare oil and sweat because they take been washed abroad with the lather and water. This results in a much less pronounced fingerprint. You lot might take had difficulties in collecting this fingerprint or may not have found one at all. On the other manus, if you utilise mitt balm, which contains lots of oil and fat, this volition brand your fingertips much stickier, leading to a much more pronounced impress. You should have seen a big fat fingerprint once you applied the powder to the surface where had you lot pressed your finger. If you compare all the prints you collected, the one with paw balm should be most visible whereas the impression with your washed hands should be barely visible.

If yous did the extra activities, you might have noticed porous or rough surfaces or materials such as paper or textiles are not very good for collecting fingerprints. Considering your results, where would yous expect for fingerprints in your home? Did you find some?

Cleanup
Clean out your castor, wipe your fingerprinted surfaces with the dust fabric and dispose of the used baby or cacao powder in the trash.

More to explore
How Does Fingerprint Powder Work?, from Scientific American
How Practise Different Surfaces Affect the Preservation of Finger Prints?, from University of California, Santa Barbara, ScienceLine
Science Activities for All Ages!, from Science Buddies

This activity brought to you lot in partnership with Science Buddies

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