I am SO sorry that I didn't check back to answer questions. I have no idea why I didn't come back to see that I failed to post details. You are supposed to be able to read my mind, don'tcha know? LOL
I have a front loader washing machine .
I WASH REDS, DEEP PURPLES, BLACKS separate from lighter colors. Supposedly you can do darks and lights together if you use Color Catchers (made by Shout, located in the laundry products aisle of the grocery store).
I do a load with all the really dark dyes together after I have soaked each one individually in the sink to see how much they run. Some will only bleed a little, but if I have one that won't stop after about 3 soaks in the sink, I won't use it at all. It often means the dye is inferior, but that seldom happens with quality quilting cotton.
1. Set the water level to high and the temperature to COLD for DARKS or WARM for all others.
2. Place 2-3 Color Catcher into a zippered mesh lingerie bag and toss it into the back of the (front loading) washer.
3. Let the machine start to fill while you stir the mixture into a glass measuring cup.
4. Pour the mixture into the machine and then add the fabric.
5. Depending on how dark your darks are, you might want to set the machine for a double rinse.
The color comes out on the Color Catcher sheets. Discard the sheets before putting your load into the dryer. (It won't hurt them but it's not necessary.)
From what I hear, it's the vinegar that stops the bleeding of colors. I believe it, because when I added just 1/2 cup vinegar to a half gallon of water (more or less) in my bathroom sink, the presoaking was a cinch. Each dark color seemed arrested.
Hope this info helps. By now you've probably all Googled it and thought I jumped ship after sharing my recipe. Sorry again. Happy Color CAtching!