I'd soak it wíth something white and see if the color is picked up.
Roberta in D

"quilter" schrieb im Newsbeitrag
oups.com...
Help! I prewash everything before it gets incorporated into my fabric
stash. I usually run fabric under the faucet and stick it in a bowl of
warm water for anywhere from 5-20 minutes to make sure the water is
clear, then toss it in the washing machine on delicate. If a fabric
bleeds, I change water and do it all over again. This works really
well for me, and I don't think I've ever had a fabric that wouldn't
stop bleeding if I changed the water enough times. BUT, I've started
using batiks, and the bleeding on some of them is just terrible. I can
get the water to run clear over a fabric, but if I leave the fabric in
the bowl for a few hours or overnight, by morning the water is bright
green all over again. If I drain it and refill, it's bright green
again by nightfall. Anyway, I'm willing to slave over one batik for
days to get peace of mind that it won't bleed, but my question is
whether this is doing any damage (removing too much color) from the
fabric, by soaking it for days at a time.
thank you oh wise ones.

-Lynn