Use this product to 'fix' dyes in commercially purchased solid colored cotton fabrics or clothing to prevent color bleeding during washing. Also use to add washfastness to your own dyeing. Particularly valuable to quilters. Soak fabrics in Retayne before washing it for the first time. Use one teaspoon per yard of fabric in a HOT (at least 140º F) soak for 20-30 minutes, with enough water to cover the fabric, then wash in hot water and Synthrapol to get out any remaining "fugitive" dye. If you don't do this last step with the Synthrapol, then only wash in in cool water for life of the fabric. You do risk some fading when using the Synthrapol and hot water, as it will remove any remaining "fugitive" dye.
Further info: Retayne and Dharma Dye Fixative act to swell and positively "charge" dye molecules to improve adherence to fabric. Effective with Fiber Reactive, Direct and Acid dyes. The penalty can be some reduced lightfastness.
Dharma Dye Fixative is a comparable product to Retayne but can be purchased in larger, more economical sizes.