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*This experiment was first published in Double Helix magazine.
Double Helix is the official science club of CSIRO Education.

Have you got what it takes to be a super sleuth?
Here's a caper that will test your skills of deduction.

WHAT YOU NEED
Gather together a group of fellow crime busters. Choose a kidnapper by secret ballot.

Decide on the terms of the kidnapping, for example, your CD walkman for chocolate biscuits.

Now, leave your CD walkman out for a few hours somewhere that they can secretly find and kidnap it (but not somewhere that anyone else can come along and take it).

In order to play, the kidnapper MUST leave a hand-written ransom note!

THE EVIDENCE
Extract ink from the ransom note and compare it to the ink in pens used by the suspects to identify your kidnapper.

WHAT YOU NEED
- Absorbent paper eg: paper towelling - for both the ransom note and test strips
- A selection of different types of felt-tipped pens
- Paper clips
- A clean jar and water

WHAT YOU DO
1) Before the crime takes place, give out the pens to your various suspects. The kidnapper has to write the ransom note using the pen that you have given them.
To begin your investigation, take back all the pens as evidence.

2) Cut the paper into 2cm strips.

3) Draw a small circle 1 cm from the bottom of the paper with different black markers or felt tipped pens.

4) Fill a clean jar with about 1 cm of water and, using paper clips, dip the paper into the jar making sure that the bottom of the paper is in the water. The circle must be ABOVE the water level.

5) Watch the water rise up the paper. Different components of the ink will travel up the paper at different speeds.

6) Try out a variety of pens. If the ink does not separate in water, repeat the experiment by using methylated spirits instead of water in the jar. (ask your parents first!)

7) Time to solve the crime… who's chewing the chocolate?

DETECTED LINKS

º Where in the World is Carmen Sandiego?
Join the virtual detective agency and e-vict Carmen and her V.I.L.E gang before they commit any more computer capers.

º Doorman's Code
You must crack the doorman's secret code to fulfil your mission...

º A. Pintura: Art Detective
Ace detectives are needed to help solve the case of grandpa's missing painting.