Food colouring/lemon juice on sugar paper/bicarbonate of soda
Of course I wanted to do actual chemistry experiments! This one is to see what sort of art might be produced by acid with alkali reaction, i.e. fizzy painting. Conclusion: I should have filmed the process and might well do it again some time! The above is how it looked after drying and brushing off the powder; the below is the much cooler way it looked immediately after completion.
Attic Mirror 