When your fabrics bleed, more is ruined than just the bleeding fabric itself. Other light-coloured clothing can pick up the bleeding dye and become permanently dyed in that colour. This can become an even larger problem when working on crafts like quilting. If some of your quilted fabric squares bleed onto other fabric squares, the entire quilt -- not too mention all your hard work -- will be ruined. The only solution to prevent fabric dye from bleeding is to seal in the dye properly.
Fill up a large bucket or sink with very hot water.
Add 1 tsp of a dye sealant colour fixative for each yard of fabric.
Place the fabric into the bucket or sink and let it soak in the fixative for 30 minutes.
Turn on your washing machine and set it to the hottest water temperature. Add the normal amount of mild detergent to the water as you normally would.
Place the fabric, along with a white cloth, into the washing machine and allow it to wash for the complete cycle.
Take out your fabric and the white cloth. If the cloth is still white, dry your fabric as you normally would. If some of the dye transferred onto the fabric, repeat Steps 1 through 5 once more.