Before using an acid dye (More about acid dyes and where to find them), soak your material in 1/2 water/vinegar solution for at least an hour.After that you will be adding dye to water and heating the mixture in some way.The following is a list of a few different ways to use acid dye.
"My wife threatened to dye my bike shorts pink if I didn't take out the trash.I told her that they were spandex, so she couldn't dye them if she tried. "Synthetic fibers can be difficult to dye, because they are substances that have been man-mad in a laboratory, then mass produced in factories.These materials vary greatly in their chemical makeup, so a specific dye may be required for each type of material.By Rain Blanken Question: How to Dye Protein Fibers"I know that my cashmere sweater is a protein fiber because it came from an animal. "Answer: Protein fibers are all fibers that come from animals, including feathers and cashmere [List of Protein Fibers]You can not cold water dye protein fibers, with the exception of silk.Silk can be dyed just like plant-derived fibers (cellulose fibers) using a fiber reactive dye.
Other protein fibers are just too sensitive to the high p H levels involved in the easy cold water dyes, like those used in tie dye.
For protein fibers, you will need a hot bath and a 'mordant', which is just a fancy word for 'the thing that helps it stick'.
In the case of protein fibers, acid is used to help the dye stick.
We are talking some common acids here, not melt-your-face-off kind of stuff.
Vinegar and citric acid are among the most popular acids used in acid dye.
While these are mild acids, you should still use caution because vinegar can eat through skin if left on for too long, and you don't want to go getting it in your eyes.