I have tried a similar process on some very yellowed air vents, I filled a laundry tub with 50% bleach and 50% water, after soaking for a full day the plastic is still a bit yellow but only half as bad as before. Do you recommend trying to let it soak a few more times? I think the problem may be the lack of sunlight in the laundry.
Hi Ben, thank you for your message. Light is an important ingredient for the process, so a transparent container is recommended.
If you are going to give it another turn, please was the parts well. The detergent forms a residue on the plastic and it builds up after each soak. And the more it builds up, the harder it is to remove.