I have heard that the excess dye that sometimes comes from batiks is just excess dye left over from the dying process - it is not dye actually bleeding out of the fabric so you won't wash it white! :lol: IN other words, repeated soaking and washing until the water runs clear will get all this excess out.
I prewash my batiks in the washing machine with a piece of white calico to test if they run, if the calico comes out stained, I wash again with a new piece of white calico and keep doing this until it stays white. I've never had to do this more than twice. I put a small amount of detergent in but no softener.
I've also read that salt and vinegar doesn't work these days as the components in the modern dyes are chemical rather than vegetable. There are ppl who still swear they do but it is probably the soaking in water that is doing the trick - the salt and/or vinegar is redundant. :-D Retayne works because it is also chemical. But personally, I'd rather wash that excess dye out than try to fix it in there.