Your leaf looks green. But green is actually a disguise.

Chlorophyll absorbs red and blue light and reflects green back at your eyes — the same absorption principle behind the coloured paddles in [Colour Smashers]. 

But hiding underneath the chlorophyll are other pigments: carotenoids (yellow and orange) and anthocyanins (red and purple). Chlorophyll is so dominant it drowns them out completely.

The alcohol dissolves those pigments out of the crushed cells. 

As it travels up the paper, lighter molecules travel further, heavier ones stay low. The result is bands of colour — one for each pigment — separated by the paper. 

This is chromatography.

The coffee filter gives a blurry result because its fibres are uneven. Chromatography paper gives sharp, distinct bands because its fibres are perfectly uniform — the same principle used in forensic labs and pharmaceutical testing.

And those autumn colours? When trees stop producing chlorophyll, the green fades — and the hidden pigments finally show through. They were there all summer. You can see light absorption working from a completely different angle in [What Colour Is Your Shadow].

Curiosity spark: What do you think would happen if you ran this experiment with a leaf that has already turned red or orange in autumn — would you still see the same bands, or completely different ones?

Find out in The Crazy Scientist Lab.