Combining iron and alum mordants for eco-printing

Although iron is my trusty favourite mordant- easy to make, relatively low toxicity, and easy to dispose of- I have been experimenting with alum lately. My first results of eucalyptus on alum were not very promising. Fluro yellow is not my favourite colour. But then I tried double-mordanting, combining both iron and alum. I hoped that the saddening effect of iron would help tone down the brightness of the alum and bring in more subtleties. And it worked beautifully!

Double mordanted with alum and iron

The alum has brought out these beautiful oranges and yellows from the eucalyptus leaves, while the iron gave more depth and detail.

How to mordant cotton

This onesie was bit of a failure originally. It had pale, faded grey prints, probably from not being scoured properly. The alum and iron mordanting prepared it well for a second round of eco-printing, and it was transformed into one of my favourite pieces so far. Aren’t the gumnuts exquisite?!

Mordanting cotton with alum and iron

To do this double mordanting, I scoured the cotton, gave it a short dunk in one mordant, let it dry and cure, then dunked it in the other. Then I eco-printed the fabric in my usual way, using the instructions I share in my ebook Gum Leaf Alchemy.

I haven’t yet tested to see if it makes a difference to do either the iron or the alum first. It is definitely worth continuing to play with this combination!

Combining alum and iron mordants to eco-print on cotton

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