Quote Originally Posted by Dall_Piobaire View Post
Oh, I thought the soda ash kept the dye from fading. Glad you said that Lady MacKay!
Soda ash (sodium carbonate) is used as a fixative for fiber reactive dyes. It won't do a thing to make an "all-purpose" dye like Rit permanent.

(There are different sorts of dyes to dye different sorts of fiber. Protein fibers (wool, hair, nylon) require an acid dye. Cellulose fibers (cotton, linen, rayon) require a different sort (fiber reactive). Silk can be dyed with many dyes; Polyesters and many other synthetics require special dyes, and aren't generally dyed by hobbyists. Rit (at least the sort sold in grocery stores; they make others, I don't know.) is an all-purpose dye that's a mixture of an acid dye for wool and a direct dye for cottons. Soda ash might fix the direct dye (I don't know what Rit uses these days; and it probably varies from color to color), or it might not. But it sure won't do anything for the acid dye. And if you're dying wool, you've got the opposite problem. If the thing you're trying to dye is a single fiber, it's worth the effort to track down a suitable dye for the fiber. Rit's popular because it works on lots of stuff, not because it actually works well.)