Heating Procion MX Dyes and Science Sundays

While discovering that Procion MX dyes are very happy to dye wools, I came across something else that gave me pause for thought. Although there’s not a wealth of information on using Procion MX dyes with acid, most of the advice that is out there says you need to steam or heat the fibre after applying the dye.


For acid dyes, heating the dyebath is standard practice to help fix the dyes. Fibre reactive dyes, like Procion MX, don’t require this, which is definitely an advantage when trying to do large bits of tie-dying. The standard advice when working with fibre reactive dyes on cellulose fibres and silks is to do your dyeing, then leave your fibre damp with the dye on it for at least a good few hours, closer to 24, if you want strong colours.

As I tend to like very intense, saturated colours, I tend to err on the side of giving the dye a longer reaction time.  For some short-sighted reason, I’d always assumed that there was some kind of degradation of the Procion dyes at higher temperatures, hence leaving them to react at ‘room temperature’ but seeing as steaming the wool lately with Procion dyes had worked just fine, that obviously couldn’t be the case.

Was there really a way to go speed up Procion dyeing so I didn’t have to wait so long to see what wonderful mess I’d made?

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Happy Accidents and Confusing Chemistry

After the exciting delivery of some new Kemtex colours and picking up some new ideas at Wonderwool, I have been eagerly awaiting the chance to dye some more silk. I normally paint the silk in a relatively random fashion but I wanted to try something a little more sensible and to have a go at making some colour gradients.

I spent the morning remaking all my old dye stock solutions and making up my new colours as well. Previously, I had been using white vinegar as my fixing agent but I wanted to try using citric acid and adding some urea. The purpose of urea is to increase the solubility of the dyes (therefore allowing you to make higher concentrations) for brighter, more intense colours as well as helping to keep the fibre moist, particularly during the fixing stage.


It was while making up the dye stock solutions that I made a mistake I wouldn’t realise until much later… I made up approximately 5 % dye solutions, added the citric acid and the same amount of what I thought was urea, as recommended in the Kemtex instructions. I’ve heard a lot of people saying they use 2 % concentration dyes for painting and 1 % for immersion dyeing but I have never found concentrations that low give me quite the colour I wanted, hence the higher concentrations.

Counterintuitively enough, most chemical dyes are actually not very water soluble. Certain dyes, Kemtex Black for example, are notorious for being difficult to fully dissolve. This is problematic because unless you want to start filtering your solutions, undissolved dye means you have no idea what the concentration of your solution is and makes it difficult to get predictable, repeatable results as well. I’ll talk a bit more about the chemistry of all this later but back to playing with colour…

I gave the silk a rinse in cool water before I left it to soak overnight in water with a lot of citric acid added. The silk I have isn’t pre-treated and the previous batches have been really clean so I didn’t worry about scouring it thoroughly. I made sure the silk was relatively dry before I start applying the dye, as I didn’t want any additional dilution of the dyes.

After the poor results with the black from my last set of silk dyeing, I was keen to see if the combination of citric acid and more concentrated solutions would fix this, so I started with some pure black in the corner trying to work through dark to light purples before going to magenta/pink at the end.


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