Tannin

Maple leaves are high in tannins and so are well-suited to the eco-print process. Tannins help natural dyes bond to fabric and often also impart colour. Tannin levels increase over the growing season. So maple leaves picked in autumn will print more vividly than those picked in spring.

The different sides of maple leaves produce quite different effects. I like the delicate details of the sky-facing side of the leaves:

But the earth-facing side will produce darker prints and be more colourfast:

Before eco-printing, I soaked the maple leaves for a month to get rid of excess tannins, which bleed when combined with the iron mordant. The soaking process helps produce clear, crisp prints. Find out more about which leaves can be used for eco-printing on cotton and how to prepare them with my ebook, The Leaf Guide.