The general consensus seems to be that you should use a mordant to encourage the colours to stick when making eco-prints. Alum (potassium aluminium sulfate) (Amazon) appears to be the mordant of choice so I dutifully ordered some along with some acid-free watercolour paper (Amazon) which I hoped would be robust enough to cope with the steaming.
After deciding there was no way that I was going to get the A4 paper into our small round vegetable steamer I hunted around for an alternative. I bought this old fish kettle years ago at a car boot sale, and it’s sat on the top of a cupboard ever since so I am delighted that it is finally getting some use! We could fit our paper in the steamer by folding it lengthways, so that’s what we decided to do.
And here are our finished eco prints