after lots of attempts and researching..

[Tais]

for around 4 years since unyellowing the yellowed plastics were discovered, i've had lots of failed attempts in reversing the yellow color back to its original color, using UV light, dipping in bleach and hydrogen peroxide solution, dipping in chlorine bleach solution, setting a UV concentrated bucket with another bucket inside filled with H2O2 and bleach solution until the final attempt which was proven successful, which was the hair dye peroxide bleach!

a lot of those results ended up with partial unyellowing, no unyellowing and dullness of the canopies..



the procedure i did which was proven success needed a few things only:

sunlight
plastic bag (the large zipper sandwich bags are the best), must have no openings so water doesnt vaporize
hair dye peroxide bleach (12% concentration)
the yellowed plastic
vinyl gloves (bleach is an irritant)
any clothes that is not of any importance (in case u got stained and there were some undesired results)


first the cream is rubbed all over the yellowed plastic (vinyl gloves must be worn)
then place in the plastic bag, must be sealed, and try to keep it having less air than usual (in case water vaporizes it doesnt open the seal or explode).. tightening the plastic bag or wrap around the areas to be unyellowed may lead to undesired results, such as unbalanced unyellowing
place it under sunlight away from contacts or shadows

these 2 SMC canopies were the first 2 successful attempts with unyellowing, it is back to white though it has a few yellow stains remaining!

[Jordan U]

Those look pretty good.. While not perfect, I imagine whatever yellowing is left will be a lot less obvious once the fans are installed on the ceiling..