– Alum mordanted yarn hung out to dry, after making a rediscovery in my own stash. There might be some plant dyeing happening around here after all! I was inspired to begin with these. A plant that I’ve tried to get rid of in my horse paddocks, but I’m sure I can find some still. Result report guaranteed if and when!
I often come upon blogs about plant dyeing, usually beginning dyers, mentioning how they mordant their yarns with vinegar or salt. Don’t get me wrong, I’m not rallying against beginners, like myself!, posting about their passions and experiences. But this being a pet peeve of mine, I’m going to mention it again: Those are NOT “mordants”.
A mordant is something which “opens” up the fiber to soaking up more dye stuff = colour as well as keeping it there, making your yarn more light- and wash fast. Usually it’s a metal salt, alum, iron (which I think works better with alum too); also copper and tin which are quite poisonous and chrome which is actually not available in many countries as it can alter your DNA. Not worth the trouble imho. I have a very small jar of tin salt to get deep, bright reds from madder, that’s it.
Vinegar can in some cases be used as a modifier = alter a colour which is pH sensitive. Mostly it does nothing however, but your wool does love you for not throwing it into an alkaline bath, which will break down the fibers eventually. (so will iron btw)
Salt? Is used in dyeing cellulose fibers with synthetic fiber reactive dyes. In plant dyeing? Hell if I know! And yes, I’ve added salt to a couple of dyes just because, and well. Nothing.
I’ve also dyed a few skeins here and there without alum mordant to get pastels and to compare. Top row are the same bath, with mordant. These skeins have been hidden away in a box, but kept in sunlight, the unmordanted versions also fade more easily than the others. These were just what I could find today, the really pale ones are long gone.
So my recommendation for obtaining pale colours is: short dye baths, low plant to yarn weight ratio or use the dye bath multiple times. But do make the effort of alum mordanting everything. (the exception being woad and indigo dye, which is a completely different story anyways)