Way back in December I was thinking about hot and cold mordanting processes. I decided on an experiment inspired by a post by Leena at Riihivilla which led in turn to a blog called From Silk Road. There, Jarek shows experiments with solar mordanting over 28 days, and one of the mordants he is using is Himalayan Rhubarb. Mine is the good old fashioned European eating kind… but perhaps the same principles could be applied? Jenny Dean certainly describes cold mordanting with alum and I have tried that previously with success. I was also curious about the findings of Pia at Colour Cottage. She has undertaken some experiments with rhubarb leaf mordant here and here and found it made no difference to dye uptake or lightfastness. So disappointing!
I started with 1100g rhubarb leaves (and stewed the rhubarb with orange juice to go with waffles… mmmm). Way more rhubarb leaf than necessary for the job, I think. I have no way to know if I am even using the same rhubarb as Pia… but I decided to err on the side of plenty of rhubarb leaf and not committing a huge quantity of yarn. I created two, 25g skeins of Bendigo Woolllen Mills alpaca rich ‘magnolia’, left over from some past workshop I ran. One was subjected to the classic heat treatment in rhubarb leaf solution (45 minutes on a bare simmer), left overnight to cool down and rinsed out.
The other went into a glass jar for a solar treatment, which was quite hot at times. It went into the jar on 16 December and our first 40C day of the year was scheduled for the 18th. I created two more skeins and mordanted them in alum, one using the hot process and the other packed into a bucket with a lid in the sun. Here is the solar mordant rhubarb jar (and some iron soaking in vinegar water on the left), in December. They’re sitting on a concrete surface with a concrete wall behind them. I’m trying for thermal mass in a sunny spot.
Things being what they are (by which I mean I have been too busy to think much about this experiment), I took the yarn out on 13 April 2014. Here it is before removal. There was a little layer of mould stuck to the lid, for those who are wondering. In retrospect, this would have been a great application for Stuff Steep and Store.
Here is the yarn after removal from the rhubarb leaf solution. I’d call that a dye and not only a mordant!
Here is my solar process alum-mordanted yarn after similar neglect for the same period of time.
Finally: my full selection dry and ready for use: no mordant, alum applied with heat, alum applied through solar process, rhubarb leaf applied with heat, rhubarb leaf applied through a solar process.