Dyes from Red Onion Skins on Wool, Cotton and Silk

Though their own visible colour is a rather gorgeous purple, red onion skins are generally reported to give dull results when used for dyeing. None too thrilled by the dye results pictured out there on the internet, I've stuck to dyeing with the brown type of onion skins. However, having written an onion dye project for January in the Plant Dyes for All Seasons 2017 Calendar, I thought it was high time I checked the red skins out myself. With a mere 14g saved up in a paper bag, a small trial was all I planned. I made up a 10g skein of laceweight merino, cut a square of cotton from one of himself's old shirts, salvaged a little offcut of jersey silk and put them in a bowl of water to soak while I simmered the red skins for an hour in one of my casserole pots.  

The following day, I sieved out the skins. Though the dye bath looked an alluring deep red, I wasn't fooled. Dye baths that look red are sneaky buggers, I've never had red wool come out of anything but madder root dye, though I have had yellow, green and even blue from the wine red baths you get from simmering hollyhock flowers. My unmordanted samples were simmered for an hour and left in the dyebath overnight. Sure enough, no red to see next morning - here is what the results looked like.

The merino wool was an unremarkable brown, but the strip of jersey silk had taken on a rather lush shade of purple brown and how on earth did that cotton come out green, which is brighter in real life than my camera shows? I tried dyeing a number of small pieces of this cotton in the afterbath and they came out in a series of pale green to deeper green, depending on how long they had been simmered for. One more very successful rummage in a practically empty tray of red onions at the supermarket got me a massive 48g of red onion skins, enough for a proper dye project in my large dye pot. The thrill of this adventure dissipated as I pulled a lovely 50g of expensive silk jersey out of the simmering dye bath by degrees, revealing a gradient of plain brown, a colour much like the wool skeins. 

Later, a nice white cotton T shirt simmered in the afterbath just turned beige. I was sure it wasn't because of overheating the dyebath - my usual conclusion when I get an unexpectedly dull result. I had been scrupulous about monitoring the temperature for an exact hour of simmering. Where had that purple hue on the silk gone, why wasn't the T shirt green? Wondering if the green effect had something to do with the type of cotton, I guessed the previous cotton might have been mercerised.

Making a little test bath with a further 10g of red onion skins in a kitchen saucepan, I dyed small skeins of organic cotton yarn, mercerised cotton crochet thread, a strip of cotton T Shirt, a snippet of calico and another piece of the cotton shirt I had cut the original samples from. All of them came out red-brown, except the cotton shirt sample, which came out of the strong dyebath khaki green.

Well, this suggested the green did have something to do with that specific cotton shirt, but I don't know what. After my salutory experience with brown onions skins, which seem to dye best when boiled, I boiled up this red onion afterbath for a good long while with tiny skeins of laceweight merino wool yarn, bits of alum mordanted silk and short lengths of cotton yarn. Actually, I forgot I had left the gas on and damn nearly boiled the saucepan dry.

Boiling cleared the colour from the dye bath and put deep colour into the wool and pale colour into the silk, while the cotton came out with hardly any dye at all. Once again, not what I expected. I thought that silk took up dye best and would have been most strongly coloured and I can only suppose the wool sucked dye back out of the cotton.

Attempting to get some clarity through a standard set of experiments, I got my proper dye pans out to reheat these samples with alkali, which deepened the brown wool and turned the pinkish silk a shiny khaki, then iron and copper solutions, which darkened the colour, copper more so than iron. In the picture, the bottom skein is the unmodified original.

Scrubbing out my dye pots afterwards, I thought how stained they had got over the years. Then light dawned - that disappointing brown jersey silk colour had been simmered in a dye pot quite probably contaminated with residual iron from a previous dye session. Once I had collected another 80g red onion skins, I simmered them in a big cooking pot that has never been used for dyeing, as I am satisfied that onions are definitely food safe. 

Dyeing another piece of jersey silk, as I pulled out a little more from the simmering dye bath at frequent intervals, a gradient appeared that initially looked pink, deepening to red, with no sign of purple. As it cured over a few days, the colour on the silk shifted toward brown. Because it was a richer red shade than the first brown silk, shown on the right of this photo, I think that pot probably did have a bit of iron left in it. 

Dyeing a cotton shirt in the afterbath of the clean red onion skin pot, I got a khaki result, rather than the greens I had first time round.
Where did that purple and green go? Maybe the first small trial batch of onion skins came from a different kind of red onion. No way I can find out, the supermarket price tags always say simply 'Red Onions'. At any rate, onion skin dyeing has brightened a dark season. Here is a glamour shot, brown onion skin results on the left, red on the right. Change and decay, in all around I see. With no mordant, I wonder - how long will onion colours abide with me?