Along with the pre-dyed skein of merino that had been lying around for a year, I also decided to experiment on some fresh yarn this year once the egg dyeing was done. In an attempt to do it right this time, I attempted to mordant four skeins of superwash merino in a solution of 10% alum and 5% tartaric acid (by weight of fibre), because that was what I'd read on the omniscient Internet. I heated it all up and let it simmer for an hour or so, let it sit to cool, and then did the dyeing thing.
One of these skeins was destined for the turmeric dyebath and behaved as expected. The three that went into the logwood bath... not so much.
This is what came out of the purple logwood brew:
It was a rather nice shade of khaki, actually, but how this colour could happen is beyond me. Also, it didn't seem to be significantly more colourfast than last year's unmordanted skein.
At this point I began questioning the wisdom of combining alum and tartaric acid for the mordanting. Alum is a base and tartaric acid is, well, an acid, and surely the two would react as they did in my high school science lessons, by forming a salt and water, leaving precious little active ingredient to work its mordanting magic on the yarn? I decided to try re-mordanting my dyed skeins in just alum to see whether that would help with the colourfastness. In they went again, with 10% alum by yarn weight, to simmer for an hour.
Ten minutes into the process those khaki skeins had dyed the water a shade of magenta so deep I could barely see the yarn, and the yarn itself now looked like this:
Deep mulberry. Definitely the sort of thing I'd been hoping to achieve all along from the logwood infusion, but how that medium shade of khaki could turn into a shade of purple so rich and dark just from simmering in alum, without as much as a molecule of extra dye being added, is pretty mystifying. (Not that I'm complaining.) But this time the alum seems to have done its work, because after I'd simmered this stuff for an hour and left it to cool a little -- I was too impatient to wait for more than an hour before taking it out -- the water ran off clear after just a few rinses.
What was left in the dyebath -- and note, again, that the only colour in this so-called dyebath was what had bled out of the khaki skeins during re-mordanting-- was still so luscious a hue that I decided to try putting another skein in. I added extra alum as this skein hadn't been previously mordanted, and duly simmered again.
The result is a very nice shade of lilac:
and the skein behaved similarly to the dark purple ones during rinsing, which seems to suggest that doing the mordanting and dyeing in a single operation will work rather well with logwood.
Oh dear. Now I want to dye enough to make a whole sweater!