Jacquard's iDye Fixative is a post-treatment for dyed fabrics. It aids in retaining color intensity over time while lowering the chance of back staining or color bleeding when washing. It is intended for items that will be washed frequently or have incredibly intense colors. iDye Fixative can be used on most 100% natural fabrics such as silk, cotton, linen, and rayon. Not for synthetic fabrics. Available as liquid (3fl oz jar) or powder packet (0.49 oz).