Fabric and salt water?
 

I just have to ask this. I was with a friend today and she told me that she pre-washes her newly brought fabric in 2cups of salt water. This "sets" the dyes so it won't bleed. This was a tip she got from her mother.
Has anyone done this?

No I haven't. But I do believe RIT dye says something about this.

This is what the company that makes RIT dye says.
"For more intense color when dyeing fabrics containing cotton, rayon, ramie, or linen, add 1 cup salt to the dyebath. When dyeing nylon, silk and wool, add 1 cup white vinegar to the dyebath. If possible delay adding the salt or vinegar until 5 minutes after the fabric has been in the dye bath. The delay will help to promote level dyeing.
Add 1 Tablespoon laundry detergent to all dye baths to help promote level dyeing.
The longer the garment is immersed in the dye bath, the deeper the resulting color. Items can remain in the dye bath up to 1 hour as long as the water remains hot. You'll also have to make sure the item receives constant agitation or stirring."

So your friend seems to have a good idea. I may try this.

Salt water was used in the past to set some organic dyes. It does not work on today's commercial dyes, which are chemical in nature. The salt doesn't hurt anything, but it also doesn't "set" any dyes in modern fabrics (unless they happen to be hand-dyed with organic substances, which is very unusual).

ditto to Prism99

Retayne will set your fabrics, and prevent bleeding thereafter, if directions are followed.

My DIL does this on denim jeans before wearing them and says they keep their original color better.

I soak my fabric in a salt vinegar, and alum solution. I've done this for many years and my clothes keep origial color better than others that are not soaked ,sshshhhhsshh don't say it too loud that it doesn't work, cause so far it has.

Yes it works. The salt and or vinegar sets the dye

My mother taught me to use both salt and white vinegar.

Salt and vineagar are both good. Way back when, dyers used to use urine(!!) I would rinse it out later though, as salt can deteriorate fabric over time.

I have not done this but my daughter bought a quilt at the Ozarks and it said to wash it with 2 cups of salt. She asked me about it and I didn't know anything about it. It said that the salt will set the dyes, guess I need to ask her about that.