Name: Jemima 
Message: How  do  you  block  the  color  of  cotton  blue  jeans  from  bleeding?

You really can't. Blue jeans are usually dyed with indigo, which is a dye that cannot be chemically fixed in place after the dyeing process is over. Properly applied indigo should not crock or bleed, but if too much indigo is applied at one time, it will not get inside the fibers and will tend to come off. It is important, when dyeing with indigo, to use multiple dips into a relatively weak dyebath, instead of one dip in a very concentrated dyebath.

For clothing dyed with dyes other than indigo, you can use a commercial dye fixative such as Retayne, which sticks to negatively charged dye molecules, but indigo dye molecules do not have a negative charge and cannot be fixed with Retayne. In addition, the dye catchers (such as Shout Color Catcher) that you can throw into the laundry to pick up stray dye will probably not work for uncharged dyes such as indigo.

Neither vinegar nor salt, often recommended by the ignorant as dye fixatives, will help to fix the dye at all.

What you should do is wash the blue jeans several times, using the hottest water recommended on the care label. If they continue to bleed dye after that, return them for a refund to the retailer from which you bought them, because they are defective.

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