"Slippery Ink"
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Aim: This is to demonstrate the effect of chromatography - the separation of colours of texta or normal ink.

Equipment: The equipment includes...  

• beaker or glass;
• texta ink or normal ink;
• filter paper or absorbant paper;
• water.

Method: Soak a strip of filter or absorbant paper in water. Then half fill a beaker or clear glass with ink and place the wet strip of paper over the lip of the glass so that one end touches down into the ink and the other hangs over the lip of the glass. Let it stand for a number of hours (or overnight). The normal black or blue ink separates into a rainbow of different colours.

Background knowledge: When they commercially make ink they actually mix a variety of different coloured ink together to obtain blue or black ink. The coloured inks are all of different weights and therefore when the piece of wet paper hangs over the lip fo the glass the lighter molecule types of ink can move up the strip higher against gravity whereas the heavier molecule types of ink cannot.