The red colour of some fabric must be set, or made permanent, to avoid bleeding of the dye colour. Fabric manufacturers often use excess red dye to achieve a bright red colour. The excess dye cannot set into the fibres. Silk, cotton and linen are the most difficult fabrics in which to set red dye. Nylon, acrylic and polyester are less problematic. Bleeding happens when unset dye leaves the fabric when placed in water. One red sock in the washing machine can turn a load of white towels bright pink. If a fabric bleeds, the dye was not set, and it is impossible to reverse the process.
Wash red items in the washing machine with three cups of white distilled vinegar and mild, non-bleaching detergent, like Fab or Dynamo. The vinegar will help set red colour in fabric.
Wash a second time with mild, non-bleaching detergent on a hot water cycle. If the fabric is not suggested for hot water wash, use warm water. Do not soak. Red fabrics should be agitated in a machine that is not overfilled to prevent streaking.
For subsequent washes of any red-coloured fabric, sort into a "dark" load. Red fabrics should be washed with blacks, and other reds, pinks or oranges. Sorting will avoid unset dye bleeding onto lighter fabrics.
Simmer red-coloured fabric in a large pot, with enough room to submerge the fabric in water, on the stove. Mix water, one cup of white distilled vinegar and 1/4 cup salt. Place the fabric in solution and simmer for 20 minutes.
If using commercial dye, instructions for setting the colour may differ slightly; follow the suggested procedure.
Wash in hot water in washing machine with non-bleaching detergent, red fabrics only.
Wash red fabrics at the end of a load cycle to minimise dye bleeding. Commercial dye-setting products may increase colour fastness and reduce colour loss. Follow directions and test before washing with other items.
Many red colours can never be completely set. Wash red fabrics only with dark or like colours.