Message: Do you have any information about the composition of union dyes, in terms of the ratio of acid leveling dye to direct dyestuff? I'm trying to mix my own for dyeing blends, and would like some idea of where to start in terms of how much of each type. Any advice? Thank you! 

I've never seen any information on this anywhere. The one thing I would recommend, which you've probably already thought of, is to measure the dye by weight, not by volume, for greatest reproducibility. Different dyes, and even different dyelots of the same dye, have different densities, so measurements made by volume are not as consistent as those made by weighing out the dye.

ProChem recommends 1.2 grams of their Kiton acid leveling dye per pound of fiber for a pale color, 4.5 grams for a medium color, 9 grams for a dark color, and 25 grams for black, while they recommend 0.5 grams of their Diazol direct dyes for a pale color, 2.25 grams for a medium color, 9 grams for a dark color [this must be a misprint], and 13.5 grams for black. Except for that anomalous dark quantity for direct dye, the ratios are about 2:1 by weight, for similar impact. 

So, it looks like a ratio of 2:1 by weight would probably be a good start, at least if you're using bulk acid leveling dyes and direct dyes from ProChem, which is a very satisfactory supplier. However, suppose that you dye a fabric blend that is 33% protein fiber and 67% cellulose fiber. Then it would make more sense to adjust the ratio of dye weights, accordingly. 33% protein/67% cellulose would call for equal weights of dye. 67% protein/33% cellulose would require four parts acid dye to one part direct dye.

For perfectly equal results, you'd need to allow, as well, for the fact that nylon takes some acid dyes more brightly than wool does, and vice versa for others, or for the greater brightness of mercerized cotton as compared to unmercerized cotton. How confusing it gets!

I think that the simplest thing would be to compromise on using twice as much of the acid dye by weight. Since it's likely that you will not know in advance how much of each fiber you have, nor how brightly they will take the appropriate dye, there's not a lot of point in fine-tuning beyond that.

If only you could get hold of some of the syntan reserve agent that the makers of Alter Ego dyes add to their dye fixative in order to keep their direct dye from staining the protein fiber. Then you could make good mixtures that dye the different fibers in different colors. I don't know of any source for the reserve agent, though. I'm sure it's available only in huge quantities. I know that's not what you're asking about, but it's such an interesting idea that I can't help but throw it out there.

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