I’ve been messing about with dyes a few times now, and thought I could try woad, which was popular in the medieval and post-medieval period for dyeing cloth blue, or using it with other dyes to get green or black or suchlike.
Unfortunately, getting hold of woad leaves is tricky and expensive, it is easier to try with the (chemically identical to the historical stuff) indigo pigment you can buy in powder form. Unfortunately the preparation method is simple, yet difficult to make work, because it relies on having a pH of around 9 and a lack of oxygen in the water bath. I was roughly following the method in “Colours from nature” by Jenny Dean, but right at the start it didn’t work, since the instructions to mix indigo powder and washing soda (Sodium carbonate) in hot water just didn’t happen, insofar as the indigo stayed as gritty lumps.
It did so all the way through the heating and cooling and heating attempts I made, even when I made sure the pH was just right (There’s a reason why I have a pH meter)
After mixing the indigo solution with a solution of colour run remover, which contains sodium hydrosulphite and is supposed to remove oxygen from the liquid, and heating it for over an hour, keeping it around 50C as instructed, and never passing 60C.
Nothing happened. I added some more reducing agents, fiddled about and nothing happened, made it too alkaline by adding some lime, then added vinegar to take it back, nothing happened. The pH meter was invaluable, despite it’s probably spurious accuracy, otherwise I would have gone through a massive amount of pH paper.
Meanwhile a perfume smell stank out my kitchen because of what was in the colour run remover.
It turned out a friend sort of tried Dean’s method but used the actual chemical thiourea dioxide rather than messed about with colour run remover.
Not a good result.
So the problem here is getting the indigo sufficiently into solution, and at the moment it isn’t clear why, unless it needs to be ground to a fine powder rather than the rather gritty state it is in just now. That still leaves the stale urine method to be tried, as well as the thiourea dioxide method as well. I know that dyeing with woad is worth it, and I plan on trying to overdye some other colours, but it is proving stupidly hard to get to work.