Originally Posted by Anna.425
I have it in mind to make a red and white quilt. I have heard that dyes can be set with either warm water and vinegar or cold water and salt. Has anyone had any luck setting red dyes so that they don't bleed on the white fabrics?
The dyes commonly used on cotton fabrics work best in an alkaline environment. A small amount of vinegar (say a tablespoonful per full washer load) may help keep the pH low enough not to break the molecular bonds of the dye particles with the fabric receptor sites.
Salt does very little; it is used as a booster in a dye bath with fibre reactive dyes to make the dyes less likely to react to the water molecules, which leaves more dye molecules available to react to the fibre receptor sites.
If you're really concerned, I suggest washing with Synthrapol (or Dharma Trading's knock-off version). Synthrapol is as close to a neutral pH as a detergent can get. Pre-wash in warm water (unless you have an old pre-Energy Star washing machine; if you have an oldie, pre-wash in cold).
After the quilt has been made, wash in cold water with Synthrapol (or Dharma Trading's knock-off).