Onion skins on cotton

Another go with onion skins before I move on to the fancier ingredients (which I'll have to do since I've now completely emptied my shoebox full of onion skins). My main aims for this dye job were threefold: to figure out dyeing plant fibres (quite different from animal ones), to work out whether my last one went patchy because I soaked two different hanks together, and to use iron without turning everything completely black.

Fabric: 100g cotton
Dyestuff: 45g (45%) onion skins, mixed yellow and red
Mordant: 25g (25%) alum (aluminium potassium sulphate) with 6g (6%) washing soda (sodium carbonate)
Colour modifier: small pinch, say 0.5g (1.0%) iron (ferrous sulphate) used on only one of the hanks

The way that plant fibres, such as cotton and linen, behave during the dyeing process can be quite different to the way that animal fibres (wool, silk, cashmere) behave. In some ways the process is easier - because you don't have to be anything like so careful with the fabric - but it can be harder to get the dye to take.

First challenge was tracking down some sodium carbonate, also known as washing soda. Washing soda is one of those old-fashioned products like Vaseline, bicarb or vinegar which doesn't seem to have been intended for any one purpose, but over time has been found to have dozens of uses. The back of the bottle says To shift heavy stains from clothing; to unblock sinks and drains; to degrease cookers, pans and barbecues; to soften water for laundry; to remove moss from paths. Crikey! Is there anything it doesn't do? I'm reminded of a Mad magazine feature from years ago about finding other uses for baking soda (to dust for fingerprints; to lubricate noisy corduroy trousers...). Eventually I found my bottle of washing soda crystals at the endlessly useful Robert Dyas and it was only 99p. Hooray!

The best thing about dyeing cotton, as opposed to wool, is that it won't felt. This means you don't have to bother with all that 'put the yarn in cool water and gradually bring it up to temperature' stuff. You can just drop it into boiling water, and when you want it cool you can just throw it under the tap. This does make it all a bit faster.

To scour cotton, you can just boil it, so you don't have to soak it overnight. Unfortunately, though, this doesn't mean that dyeing cotton is vastly quicker than wool because the best way to mordant cotton is to boil it up with the alum and washing soda and - yep - leave it soaking overnight. I was a bit worried here as the alum seemed to react with the washing soda - something white precipitated out of the water and formed a sediment on the bottom. Somehow this felt strange (why are my chemicals not sticking to the yarn?) but I don't think it mattered.

From this part onwards it's all the same as wool. I did notice a significant difference, though - the dyebath didn't begin to clear while the yarn was in there. Furthermore, when I came to rinse the dye out of the yarn, masses and masses of colour came out and I had to rinse the yarn a lot before it ran (nearly) clear. This wasn't the case with the wool, to which the dye seemed to stick like superglue. I suspect this means that natural dyes are more fugitive on plant fibres - I wonder if it will fade faster?

This time I used much less iron than last time. Deciding that my kitchen scales are nowhere near sensitive enough to measure out a gramme or two, I sprinkled a little bit in instead - I'd say about quarter or half a teaspoon, maybe 1g, maybe less. I also made sure to soak and rinse my two hanks separately to prevent iron contamination crossing from the darker to the lighter hank.





Success! No dark iron-contamination patches on the lighter ball this time, and the darker one is nowhere near as dark as with the wool. I'm pleased with these results and now feel prepared to move on to some of the more unusual dyestuffs.