if you use bleach you can neutralize the bleach (so it stops bleaching) with peroxide...equal parts peroxide and water, after bleaching to the desired shade rinse well in cold water then dip into diluted peroxide. i usually leave it in for a few minutes (i do not know if time is really necessary) then rinse again in water. the peroxide neutralizes the bleaching action and stops it from damaging the fibers. i have had fun with discharge dyeing you can get some interesting results. if you are going to try it, try it with a couple different (small) pieces of fabric to see how they turn out before doing it to a large piece.
the first time i did it i was discharging blacks...and did not test first...it was very interesting to see that one of my blacks discharged to a rather bright orange...one turned an ugly brown and one was quite blue. always test ...