Did you know that the humble red cabbage has a part to play in the murky world of espionage? Where else would you find out such an amazing fact! Cryptic Finger Tips of course - where we show you great ways of communicating secretly with your friends! Yes, an ordinary red cabbage will help you to read any message written in bicarbonate of soda invisible ink. Here's how! Get a red cabbage and take off some of the leaves. You might need to break them up a little. Put them into a heat-proof jug or bowl. Then very carefully pour some boiling water into the jug or bowl. When the water has cooled right down, throw away the cabbage leaves. The resulting water is they key to revealing invisible ink - just spray it over the message. Why not give it a try? To make the invisible ink for writing a message, all you need to do is dissolve some bicarbonate of soda in water and paint the message onto the paper with a small brush. Plus, why not try pouring some of the cabbage water into the dissolved bicarbonate of soda and watch the reaction as the colour changes!