Iron mordant

Shibori eco-printing on cotton

Following on from my recent post about combining shibori dyeing and eco-printing on wool, here are some similar effects achieved on cotton. I really enjoy combining organic eco-prints with geometric grids or lines from shibori dyeing methods.

Liquidambar leaves eco-printed on cotton with iron and alum mordants

This pattern was created by folding the tshirt up into a small bundle, adding liquidambar and Japanese maple leaves as I went. Then I tied it tightly with string and submerged it in a dye bath of eucalyptus bark and iron, cooking it for about 1 hour. The fabric was mordanted with homemade iron and alum mordants, following the instructions in my ebook, Gum Leaf Alchemy.

Cotton naturally dyed with eucalyptus leaves and bark

Here is a close up of a similar pattern, this time with eucalyptus leaves and an iron mordant. The large section of lines show which part of the tshirt ended up on the outside of the bundle, wrapped tightly with string. There are smaller sections of lines where other parts of the tshirt were also on the outside of the bundle, because of how it was folded.

Creating a geometric grid overlaid with eucalyptus leaf eco-prints

This long-sleeved tshirt was also folded up, but into a smaller bundle which was pressed between two square pieces of hardwood. This helped to create a very even, geometric pattern to contrast with the organic shape of the leaf prints. This piece was also mordanted with iron and alum.

Rose leaves eco-printed on cotton by Gumnut Magic

This piece of fabric was mordanted with iron, covered in rose leaves and folded into large squares. I pressed the fabric between 2 tiles, clipped the tiles together then submerged the bundle in a dye bath and cooked it.

If you would like to come back to this idea later, you can pin the below image.

Examples of cotton clothing naturally dyed with 2 different techniques: shibori and eco-printing

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