Originally Posted by Naturalmama
Ok - how do I deal with this -- I bought some red flannel to use for the backing (this I spy is for the car so I wanted it to be warm) -- and I tested it in the hot water and it turned pink. :evil: So I will definitely wash that first, but does that mean that I will now NEED to wash the top fabric or will it still be ok not to?
I wouldn't. I would just wash the flannel. Be aware that occasionally a fabric (especially a red) will never stop bleeding dye. You need to test the fabric again after washing and drying. It has to go through the washer without pink water to be safe.
If this fabric is a bad "bleeder", you may be able to save it by washing in Retayne. Quilt shops that cater to dyers carry it, and it is widely available online. Retayne sets dye into fabric. For this reason you *never* want to use it on a finished quilt (could set a bleed); however, it is very useful on those rare occasions when a fabric won't stop bleeding.
Flannel is the one fabric that I routinely prewash and dry twice before using. This is because flannel can shrink so much. Not all flannels shrink badly. If the flannel comes out of the wash the same size, I don't bother to wash again; if it has obviously shrunk, though, I wash and dry it twice. Flannel is the only cotton fabric I know that can have this shrinkage problem. Regular quilting cottons don't shrink enough to give me any concern, which is why I don't make extra work by prewashing them.