In some cases, it is recommended that individuals who are undertaking a fabric dyeing project use a substance such as salt or vinegar to set the dye, although the exact amount of vinegar to be used and the specific method of use may depend the type of fabric being dyed. For example, a dye company known as the Rit Studio suggests that DIY fabric dyers add 1 cup of white vinegar to a dye bath while attempting to dye nylon, silk or wool, although other manufacturers may suggest using vinegar to set dye for other fabrics, such as cotton or denim.
In this context, "setting" dye refers to a chemical process in which fibers absorb and/or hold on to more dye than they might if not treated with a setting chemical. Setting dye in fabric helps ensure that the dyed color will stay through multiple washings and rinses. Some research may be necessary before carrying out a setting technique to ensure that the setting chemical does not interfere too much with the dyeing process. For example, the Rit Studio recommends that those who intend to set Rit-brand dyes allow the dye-saturated fabric to sit in the dye bath undisturbed for 5 minutes prior to adding the setting chemicals to ensure the dye is absorbed more evenly.