Chromatography is a technique used to separate soluble substances that have been mixed together. It’s normally used to separate coloured mixtures, like food colourings. We are going to use chromatography to separate these different texta colourings into the coloured pigments they are made from.

You will need:

• Paper towel
• Bowl of water
• Texta or any water soluble marker (Not permanent marker)
• Tape
• Pencil

1. Draw a line with a pencil at 1 -2 cm from the bottom of the paper towel.
2. Choose some coloured markers and draw a large dot along the line of the paper towel.
3. Tape the paper towel on a tall object. Place the bowl of water at the base so that the paper towel can soak up the water. Make sure the coloured dots are not touching the water.
4. Wait for 10-15 minutes as the paper towel soaks up water. The rising water level in the paper towel will carry the marker ink upwards.
5. Watch as all of the colours that go into each marker separate out.

The science:

Paper towel is absorbent, it soaks up water. As the water is soaked up, it mixes with the ink from the markers and allows it to move around. The ink in texta/water soluble marker is made up of a number of different coloured inks mixed together.

Each of these colours are made from a different chemical which has different properties. Some of the inks will be able to mix into water a lot more easily than the others. As the water travels up the paper towel, the inks that are easier to mix with water will travel faster. The inks left behind at the bottom of the paper towel do not mix into water as easily and will travel slower. This allows us to see what different chemical inks are put into a marker to make a specific colour.

When you try it at home, can you see the beautiful yellow and blue inks separated from green? You can also see blue inks in brown and black?

It’s fascinating! Try it and share with us what happened to the inks you use!