You can imagine how concerned I was when I realized every maroon piece in each block of my multi-state virtual bee group quilt had bled onto the pristine white background fabric during washing! Since it was for me and I used scrap fabrics, I had not bothered to pre-wash before mailing fabric bundles to our group.
The t-shirt quilt images are from a customer who also didn't prewash and used an Aggie maroon backing fabric which bled onto the front white and yellow t-shirts.
The solution: Clorox All Fabric Stain Remover and Color Brightener. I have a top load washer, and I fill it with water and pour in about 2 capfuls of Clorox All Fabric Stain Remover (I know it's much more than the directions say to use). Then I allow the quilt to soak at least over night (longer if I don't see the desired results). To date, this product has never failed to work wonders for me.
Foxtail's customer was also happy to see there was a remedy for her daughter-in-law's new t-shirt quilt, which she only soaked for about 4 hours!
Of course with all that product in the wash, you'll want to give it a thorough rinsing!
I have used Shout Color Catchers when I do mix fabrics and pre-wash, but Clorox for Colors is my go to remedy for quilts that are finished and have fabrics that bled!
I'm sure it's a great idea to prewash with Retayne (color fixative that helps stabilize dyes) and Synthrapol (removes and suspends excess dye to prevent staining other fabrics), but failing that, at least there is an easy remedy that has proven to be very reliable.
I've never used this technique on vintage quilts and no one can vouch for how older fabrics may hold up. Also, I soak clean quilts. My washer has an agitator, and I never turn it on agitate with quilts because, of course, they're extremely heavy when wet and the fabric can pull and/or tear.