Making Plant Hammer Prints on Cloth Washfast

Hammering plants in a fold of cloth releases juices more akin to a stain than a dye; although the colours seem to transfer, over time, most fade to brown, like blackberry or beetroot juice.  This photo is a year old, it shows fennel leaf still green and lemon balm, sage and mint leaves quite blurred, definitely gone brown.  If a leaf pattern prints out sharply, it might seem that in itself is worth the effort of thumping away.  When you realise the cloth can't be washed without muddying the effect, the usefulness of the whole performance is limited.  To get a dye out of the majority of plants, they need to be simmered in water.  To fix that dye colour onto fabric, a mordant is needed, which binds to fibres, then also to dye molecules.  I've done little dyeing on plant

derived fabrics like cotton, which need particular mordants, mostly I use wool or silk. These latter are easy to mordant with alum, a common food preservative also used in most deodorants.  Weigh the fabric, calculate 10% of the weight and dissolve that amount of alum crystals in a jar of hot water.  Soak the silk or wool, then leave it to float for 24 hours in a bucket of water with the alum poured in.  After a rinse, it will take up dye from a plant bath.  

The picture shows a silk blind dyed with weld, slowly fading over years in direct sun.  Though plant dyes vary widely, generally, the colours last a good long while and tolerate an occasional run through the washing machine. 
I thought hammering a leaf onto mordanted cloth must release a little dye, while admittedly, it would be a far cry from simmering that cloth in a bath with the concentrated power of a great bulk of plant material. If a hammer print is mostly a stain, perhaps even that could be fixed to fabric if the stain itself picked up iron differently to unstained cloth.  Iron, either as water in which rusty nails have been lurking or proper dissolved ferrous sulphate, is also able to mordant cloth or to modify dye colours.


I tested out a variety of leaves by hammering them inside a fold of alum mordanted white silk, then simmering the cloth in a weak afterbath of weld leaves which I had been using to make contact dye prints with iron solution added.  The silk went a weak tea colour, the prints did not lose their crispness and have all come out as darker shades of grey/brown.  
It survived a hand wash, so I put the fabric through a washing machine wool cycle at 30 degrees centigrade with wool wash liquid.  The pattern survived and though the colours were not enticing, they did not fade after a few weeks in full sun.

Grand plan, now.  A big piece of silk which had had a splodgey and disappointing dip dye in a Japanese Indigo plant vat last year was mordanted with 10% alum. One rainy day, I gathered leaves from all around the garden and settled down in the kitchen with my hammer, ready to design a lovely pattern.  Big mistake.  The leaves must have been too full of sap, under the hammer, they just squidged.  Bugger. Never mind,

on a drier day, I tried again, just experimenting with whatever plant material looked a promising shape.  I had had a vat of dried weld leaves fermenting and expected a strong Lincoln Green from overdyeing the indigo, modified with a drop of iron.  Must have heated it too much or left it fermenting too long, because the weld did not perform well, another weak tea colour instead of yellow.

Anyway, the leaf prints are wash fast. Oak, cranesbill and blackberry leaves came up darker, ferns gave the most striking pattern.  Expect I'll come back to this idea for something else, some time when it stops raining.