Today I’m working on dyeing yarn. I’ve practiced getting different shades from the same dye bath by putting skeins in at different times of the process. I’m using merino nylon yarn base with acid dye.
I let the water reach a high temp, anywhere up to 180F depending on the circumstances, and the yarn simmers for a while, then I turn off the heat and let it sit overnight.
When the yarn has absorbed as much of the dye as possible the water will still have some color but it will be translucent.
I find that letting it sit overnight makes rinsing the yarn a lot easier because there’s no runoff (when the chemical process has gone correctly and the dye has bonded to the yarn).
Another common question is “Can you use that leftover water to dye something”? Yes, and it might impart the faintest bit of color. When I dye for myself I reuse the dye bath water between batches, especially if I’m making gradients. I don’t do that when I’m dyeing yarn to sell because I want consistency between batches.
Here’s a video showing the transition to done.