I have a few white cotton shirts which turned very pale yellowish in color. I soaked them in bleach and water for several hours. It made a little bit of difference, but did not completely solve the problem. What can I do to make them white again?
I’m not clear whether the yellowing was from storage or the soaking practice you described. First, I NEVER recommend using Clorox® Regular-Bleach₂ with CLOROMAX® full strength, or in very concentrated amounts on any item or surface as very concentrated bleach can damage them. Soaking is OK, but normally I recommend 1/4 cup Clorox® Regular-Bleach₂ with CLOROMAX® per gallon of cool water and only 5–10 minutes of soaking followed by a hot water wash in detergent + 3/4 cup Clorox® Regular-Bleach₂ with CLOROMAX® wash. The liquid bleach should always be diluted because it is so strong and concentrated. Used like this, it can actually cause yellowing by either breaking down the fibers or destroying the florescent whitening agents on the garment used by manufacturers to help improve the white appearance. Unfortunately, there is not much you can do for this type of yellowing problem, but repeated washing may lessen the yellow appearance. If the yellowing is from aging, a couple of regular washes should help whiten them up.
If the yellowing continues, you might have a water quality problem. Incoming water from wells and springs often have metals that can discolor from reaction with bleach. This type of problem would require further treatment with a rust remover product like IronOut, etc.