From what I understand, Synthrapol is for suspending the loose die in the water as you wash the quilt. You also have to use hot water. I think I would sew a batik triangle to a white triangle and try to see how it reacts to washing. If the sample doesn't do well (continues to bleeds into the light fabric after Synthrapol) I might rethink my quilt. Is the batik in the interior of the quilt too?