Cabbage Blue Details

Pale Blue Merino DK

I briefly mentioned in a previous post that I spent some time over Christmas dyeing some Merino double knit wool. This was my first attempt using red cabbage as a dye stuff. I had about 700g of cabbage and 500 g of wool, so I kept some of the cabbage for a lovely crisp slaw made with apple and onion. It really is delicious. Anyway, back to the dyeing, I chopped the cabbage pretty small and added 15 g of salt to each 200 g of cabbage.  That’s about a table spoon for each half a cabbage. I covered the chopped cabbage up with between 5 and 6 litres of cold water, (about a gallon), then slowly heated it to boiling. It only needs a slow simmer, so I left it just bubbling for an hour.  By this time, the cabbage leaves are looking pretty pale and the liquid is a good purple colour. I wanted to dye the wool blue, so added a couple of teaspoons of Bicarbonate of soda to change the pH to alkali. This works like magic, and you just need to add a small amount at a time till you get the colour you want.

A quick note on pH.

Red cabbage water acts as an indicator of the acidity or alkalinity of a solution. There’s a good experiment you can do with your kids here and more explanation on the BBC bitesize site if you need it.

pH scale from very acid on the left to very alkali on the right.

Preparing the wool

As well as boiling up the cabbage, I got my wool prepped for the next step. First I tied each skein up with a length of cotton fabric.  This was just to help me manipulating the skeins so that they don’t tangle or even worse, felt. Wool is easy to work with provided you are gentle, use really light squeezes, don’t ever wring it, and only change the temperature very slowly. You can boil wool, but let it both heat up or cool down slowly. Some advise not to use wooden spoons as they could ‘catch’ on the fibres, but I found them to be ok. 

To prep the wool, I used another large pan. This time I added a small amount of liquid wool detergent and then some alum powder to another 10 litres of cold water. I should have added 8g per 100g (skein) of wool but for some inexplicable reason, didn’t add anywhere near that much. I suspect my resulting wool will be anything but colour fast. It’s for hats and cowls, so hopefully won’t need washing too much. So I should have added 40g of alum powder (potassium aluminium  sulphate) to allow the colour from the dye liquid to attach itself to the wool fibres. The detergent is to help ‘wet’ the wool. It may sound a bit daft, but water is not a good ‘wetting agent‘ which is why we need to either add some chemicals, detergents or soap, or bash or swish around any fabric we are washing.  In reality of course we do both by adding detergent and then using a washing machine to swish it about. I wasn’t about to swish the wool about so let the detergent do the wetting by leaving it overnight.

The following morning, the house didn’t smell too much of boiled cabbage and I drained the bits of cabbage leaf out and returned the liquid to the pot.  I also removed the wool skeins from their pan and rinsed them very gently in cool water and squeezed out the excess by pressing them between two large towels.

I was ready to get going.  I wanted to have a slight variation in colour so wrapped each skein round a wooden spoon and then submerged the rest of the skeins into the dye liquid while suspending the spoon over the top of the pot.  I had to add quite a bit more water to the pan to get the wool fully submerged.  I also had to add a little more sodium bicarbonate to change the pH back to alkaline and therefor nice a blue.  I suspect I didn’t rinse the wool enough.  I slowly brought the pan to just boiling and then left it to cool overnight.

The following day I again rinsed the wool and dried it using gently squeezing each skein and lying it on a large towel. Once all the skeins are on the towel, add another on top and roll up the towel/wool sandwich. I stood on the resulting tube and then removed the damp skeins and gave them a quick shake. I then left them to dry for a couple of days suspended on either wooden spoons or some wooden doweling. Despite being quite blase about the lack of smell from the boiled cabbage, the smell from the wet wool was really quite strong!  I suppose it’s not that far from the sheep but the smell only lasts a short time, till the majority of the water is gone from the fibres.  it is important though to ensure that the wool is fully dry before re-twisting it into hanks.

Despite a few tangly looking bits on each skein, they all seem to have survived the process and have twisted up nicely – though the test will be once to come to wind them into balls.  Wish me luck.  

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