you would use Retayne on the uncut fabric to set the dye. you wouldn't want to use it in a pieced item as it would set the dye that bled into adjoining fabrics. At this point, since you are already piecing, I would complete the quilt and wash it with Synthrapol, which keeps the dye in suspension so it can be rinsed away. Both chemicals are available from Dharma Trading , Amazon and others. You can also try color catchers.