Chromatography with felt tips is too difficult and too slow!

As the small boy enjoyed playing with food colouring, and mixing it to make different colours, I tried to think of another activity involving colours that he might like too. I remembered that I'd had some success with chromatography and felt tip pens many years ago (before various forms of chromatography in the lab when I did grown up science), so the baby and I tested it out at the big one's nap time...

Chromatography in progress
We made it work using IKEA's drawing paper (not high quality, it was the closest to lab filter paper that I could find in the house), and a set of Crayola felt tips ("My first washable markers").  I used the beaker from our lab set, but it'd work in any clear plastic pot (clear so you can watch it happening easily).

A good dot of the pens about 15mm from the bottom of the paper and separated by about the same distance from each other worked fine, with the paper curled into a cylinder smaller than the beaker (not touching the edge) held together with a little sellotape.  I put in about 5mm of water, and we let the colours get carried up the paper by the water.  The baby wasn't mesmerised, and in between hanging the washing, feeding him, and entertaining his desire to stand holding onto my hands, we left it for an hour.  We got some nice separation of the colours in the pen inks with the green being a nice mix of blue and yellow, and the purple being a mix of a pink and blue.  The blue has some pink in it too which was a surprise, and the orange moved as a single colour rather than a mix of red and yellow as I might have predicted.  The black had blue, red and yellow inks within it and the brown was a mix of pink and orange.  Anyway, having checked it would work, I was all set to try it with the toddler...

The results after an hour
It was a bit of a flop if I'm honest.  I tried to explain that we could find out what colour ink was really in our felt tip pens and that some colours would move further up the paper than others.  The first attempt at getting him to draw the dots resulted in some scribbling with different colours.  The second - with a little more guidance/hand-holding - resulted in some nice dots.  But it took far too long and he lost interest around the time the water reached the dots.  10 minutes later he asked to do the "proper colour science" (the one where we mix food colouring) and we took it out of the beaker.  The colour separation was already visible, but not as nice as the one I'd done earlier.

The first attempt at drawing dots...
This is one I think I'll return to when he's older.  It worked nicely in principle, but his fine motor skills weren't quite up to doing enough himself to make it fun, and the demo itself didn't give results sufficiently quickly to keep his attention.  For an older child, you could also talk a bit about what might make the colours move a different distance up the paper but I doubt it'd make sense now.  I'll give it a go again in a few months' time when his drawing is more controlled, but for now, we'll stick to mixing food colouring again.  And again.