When I first started eco-printing, I boiled my bundles for 3 hours. I got good results, so I kept doing this. But one day I noticed that after a short amount of boiling the leaves had already produced a lot of beautiful colour.
So I decided to take a more systematic approach to working out the optimal length of boiling. I made up a batch of small bundles using leaves from 3 different eucalyptus varieties on pieces of the same pre-mordanted cotton. I set them to boil, then removed them at 15 minute intervals.
I was suprised to see that there wasn’t much difference between the bundle that had been boiled for just 15 minutes (left), and the very last one which was left in for 1 hour and 45 minutes (right).
The colour of the leaves on the top sides did shift from brown to blue with longer boiling times, but the centre green and botton brown leaf prints didn’t really vary. The blue band on the right side print is from the piece of dowel that the bundles were wrapped around. This band got progressively darker and bled more the longer that each sample was boiled for, because wood has its own tannins.
Even though much of the dye has already emerged after 15 minutes, I do cook my bundles for longer, to ensure that the maximum amount of colour is transferred to the fabric and to really give it time to set. I find that about 1 hour is a good length of time when eco-printing on cotton. It’s enough time to get strong prints, while being mindful of energy use.