PRO Washfast Acid Dyes & are designed to permanently dye protein fibers - animal fibers like wool, silk, angora, mohair, alpaca, soy silk, and nylon. They have excellent wash and light fastness properties. Available in over 100 vibrant and intermixable colors. These dyes must be fixed with an acid fixative. We recommend Amonium Sulfate (for pastel to medium shades) or Citric Acid Cystals (for pastel to dark shades). Acid dyes must be dissolved with boiling water and applied at a boil for solid shade dyeing and steam set when printing, hand painting or rainbow dyeing. Two ounces (58 grams) of dye powder will dye 12 pounds (5.5 kilograms) of wool to a medium shade.