DIY CSI
In this experiment you will be making homemade detection tools to help pick up finger prints and even to detect blood stains. This will allow you to act as junior CSI agents and find out who has been where. A fine powder sticks to the oil and sweat left on the ridges of our skin and they touch objects. These ridges are what make a finger print.
To test for blood you will need:
- Corn flour
- Water
- A glass
- A teaspoon
- Iodine
- Some hydrogen peroxide, thirty percent, from the pharmacy
- A spray bottle
- And the object to test (e.g. A tablecloth with blood stains)
To check for fingerprints you will need:
- Some pencil lead
- A nail file
- A very soft brush
- Wide transparent adhesive tape
- White paper
- A saucer or a small bowl
- And the object to test (e.g. A teacup)
And last but not least ... a helping hand from an adult.
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Method to test for blood
Add about a teaspoonful or two of corn flour to half a glass of water, and stir well.
Add some drops of iodine.
The mixture will turn dark blue because the starch reacts with the iodine.
Stir well and then add about two to three centimetres of hydrogen peroxide.
Give the mixture a final stir.
Pour this mixture into a spray bottle, and spray it evenly over the object you are testing. You will have to wait a bit until the mixture takes effect.
Blood contains a lot of iron, and when the mixture comes in contact with iron, it reacts and becomes transparent.
So where the mixture didn’t remain purple, there is blood!
Method to test for fingerprints
Rub the pencil lead against the nail file to make a fine black powder.
Using a very soft brush, pick up some of the black powder and carefully dust the object.
We leave our fingerprints on anything we touch, because an oily liquid comes out of the pores in the skin of our hands.
The black powder from the pencil lead will stick to that oily liquid on the fingerprints and will make them show up.
Now stick a piece of wide transparent adhesive tape over one fingerprint, carefully lift it off and stick it onto some white paper.
You can now match the fingerprints to those of any suspect you may have!