Sodium carbonate!

Von am 11. Mrz. 2009


This is a nerdy article about cotton-dyeing..

Some of you might have been following my attempts to dye fabrics with food-colours (on my webpage) -Attempts that now seem very amateur, after what I’ve been reading the last days..:beet8

I had problems fixing the colour to the fabrics – in the pot they were bright red, but as I pressed the water out, the colour went away with it.

I tried with both vinegar and salt as fixer as I read about this in a yarn-dyeing forum online. But then I came across this:

“Vinegar is not the answer!
Many people who know nothing about this subject recommend ‘setting’ dye in cotton clothing with vinegar. In fact, vinegar can do nothing useful for cotton dyes.”

..and felt quite stupid. ..then this:

“Salt won’t do it, either
Salt can be useful in dyeing, by encouraging the fiber not to repel the dye, or by making the dye less soluble, but it will not itself fix the dye to the fiber.”

beet9
Now, I’ve learned that the problem is the pH-value. For dyeing cellulose fibres, such as cotton, linen, hemp etc., the pH (of the water) has to be raised to  10,5 to 11, (=acid) for the fabrics to take the pigment.

The usual and least risky way of doing this is by using sodium carbonate -e.g. washing soda. It’s sold as a powerful “soap” for cleaning just about everything, but there’s usually been added bleach, perfume and a variety of chemicals to it. Actually sodium carbonate can be found naturally and it’s not toxic -although acid. (According to wikipedia it’s also used for making pretzels…)

indigo-005-300x225

And that’s where the “strange, sugar-like substance” I got from the indigo-dyer in Ennde, Mali comes into the picture.. (see post “natural indigo”)

“[Sodium carbonate]…can occur naturally in arid regions, especially in the mineral deposits (evaporites) formed when seasonal lakes evaporate”

-Yes, the dyer DID tell me that they mixed ashes with mud (from the evaporated seasonal lake) but I could not understand why on earth… and assumed it’s just because “they use mud for everything”… t-t-t

well, dyeing with food has turned into a kind of chemic-project and is not at all as easy as I first assumed. But as I understand some more of it now I will try to get some pH-measure-strips and pure sodium carbonate, and then try the old beetroot-experiment again.

sources:

http://www.pburch.net/dyeing.shtml

http://en.wikipedia.org/wiki/Sodium_carbonate