Coffee filter chromatography

My Dad was a chemistry teacher, and when I was little he used to take us into his classroom during the holidays to do some simple science experiments. One of my favourites was coffee filter chromatography, and remembering how much I enjoyed it I decided to have a go with Harry. Of course the science behind it went completely over his head, but he loved seeing 'what's inside felt tip pens' and keeps requesting to do it over and over!

It is so quick and easy to do, all you need are some white coffee filters (affiliate link), felt tip pens in a variety of colours and a glass of water. If your child is impatient then I'd recommend having a practice by yourself first, as some pens work better than others. In particular it's generally the darker colours that give the best results. Basically, you are separating out the different components of the ink in the felt tip pen.

Cut the coffee filters into strips as long as you can make them. Using the felt tip pen make a largish blob about halfway down. Then dip one end of the strip into the glass of water and wait for the water to soak up towards the pen mark. As the water reaches the colour it will begin to spread out and hopefully the different inks in the pen will spread out in a nice flared pattern, with the lighter colours at the top. Place it onto some kitchen roll to dry out.

You can experiment with different types of pen and try different types of marks to see which ones give the most interesting results. You could also try using several different coloured pens on the same piece of coffee filter. Here are some of our prettiest papers: