First we cut some cheap crayons (I got ours for 18p per pack of 6 in Wilkinsons) in half.
Using masking tape we then secured them to the top of a piece canvas - you could use paper, canvas was more fun though.
Before you start ensure everyone isn't wearing their best clothes and it might be best to use aprons/overalls too.
Then for the real fun. Put your canvas on an easel and get your hairdryer out. The heat from the hair dryer will melt the crayons (a bit of science in that!) and like blowing paint with a straw you can paint in the same way with the crayons and hair dryer.
You should end up with something like this...
We liked that the crayons fell down the page and stuck so we left them there. The fact that they go back to solid is another bit of science to. Science and art mixed together, perfect!