A developer is a chemical reagent applied to fabric after it has been dyed with certain classes of colorants, such as vat dyes or diazo dyes. The initial dye may be colorless or water-soluble when applied. The developer triggers a chemical reaction directly inside the fiber, converting the dye into an insoluble, final colored pigment that is highly resistant to washing.
Heard on the job
Run the yardage through the developer bath to oxidize the indigo and bring out that deep blue.
Insider tip
Handling developers requires precise temperature control; if the bath is too cold, the chemical reaction stalls and the color washes out.