Why do we add vinegar or salt at the time of washing new clothes if colors bleed?

Most dyes are done in an acid bath. By putting vinegar and salt in the first wash of new clothes gives them a bath in ';acid'; which reinforces the dye.





Laundry soaps are 90% alkaline (as any soap is). When you wash new clothes in detergent, you accelerate the dye loss because you have placed them in an alkaline environment. Same for subsequent washes.





You may ask then why not make ';acid'; soaps? Because alkaline environments do better at solubilizing and suspending dirt. Also alkaline better helps to remove oils, fats, and proteins which make up a large part of ';regular'; wear dirt.





Any of these ';new'; products for black clothes only or any other type of ';special'; soap just plays on the balance between acids/alkalies or PH Neutral environments so that the color stays better and is enhanced by some fiber enhancers.Why do we add vinegar or salt at the time of washing new clothes if colors bleed?
I've been told the acidic content in white vinegar will help ';set'; the color in. But obviously, as you wash, the dyes will wash away too.





I've never added vinegar to my wash cycle, only the rinse cycle though.....well,, by adding it to the fabric softener compartment, which essentially is the same thing.