Message: Hi Paula -- Many thanks for an awesome site!
I'm about to try dyeing something made of "aslon", a soy-based cloth. It's super-lightweight, a set of pajamas. (Were light pink; my girlfriend hates light pink, would prefer dark grey or rich scarlet red.)

What's absolutely critical: Once dyed, this clothing -cannot- run in the washing machine, or it will turn her other clothing bad shades, and result in my immediate execution... Would you suggest going with the red or the black -- and what dye / what process? [I was originally going to simply simmer it on the stovetop in RIT liquid... But now I'm wondering if I should use RIT + Retayne fixative, or Jacquard Procion with or without fixative, or... I dunno!] Pointers to instructions on your site or anywhere else would be super :) Many thanks!

Don't use all purpose dye, such as Rit. The very most wash-resistant dye is fiber reactive dye, such as Procion MX dye, which by all reports works great on soy-based fibers, since they resembled silk chemically. (There will be a problem if the soy fiber has been acetylated, but that problem would be at least as great with all-purpose dye.) 

The Retayne Color Fixative helps all-purpose dye a lot, but it will still not be quite as washfast as fiber-reactive Procion MX type dyes.

Use the soda ash recipe for the Procion dyes, rather than the acid recipe, for maximum washfastness. (Both recipes work on alkaline-tolerant protein fibers, including both real silk and azlons such as soy silk.) If you want a solid color, use a five-gallon bucket and a lot of stirring, or else use the washing machine. Dyeing in the washing machine will not hurt the machine, but it does require a lot more dye, for a single garment. See "How can I dye clothing or fabric in the washing machine?". The Dharma link on that page for washing machine instructions also leads to instructions for dyeing in a five-gallon bucket. Using a small container for dyeing, or failing to stir a great deal, will result in uneven color tones, something like low water immersion.

Another plus for the Procion MX dye is that it does not require that you use a good cooking pot, since room temperature (70°F or above) works fine. A plastic bucket is fine. You should not reuse a cooking pot for food preparation after you have used it with a textile dye such as Rit.

In deciding between red and black, keep in mind that the stitching that holds the seams together on the pajamas is almost certainly polyester, unless you were told otherwise. The polyester will not take the dye that works on the protein fiber, so it will remain the current color of pink. Which would look better, black with pink stitching, or red with pink stitching?

Both red and black require a lot more dye powder than paler shades will. Where a recipe gives you a range of how much dye powder to use, use the largest amount for an intense color like red or black.

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