White plastic can become yellowed with age. When the white plastic that makes up your tub surround ages and turns yellow, it affects the entire look of your bathroom. Tub surrounds are expensive to replace and, unless you need or want to spend that kind of money, replacing the tub surround is unnecessary. You can whiten the yellowed plastic on your tub surround using supplies from home and the hardware store.
Fill your 1-gallon bucket almost up to the top with hydrogen peroxide. Add 1/4 tsp oxygen laundry booster to the peroxide and stir well with the paint stirrer.
Saturate old towels in the bucket with the peroxide mixture. Do not wring out the excess liquid. Lay the towels over the yellowed tub surround, allowing them to remain for two to six hours, or whenever the tub surround is whitened to your satisfaction.
Plug in and turn on the ultraviolet light, then close the door and leave the room.
Check the progress of your tub surround every hour. Open the door, turn off the ultraviolet light, then use a gloved hand to lift a towel and look at the tub surround. Saturate the towels in the peroxide mixture, if needed to keep them moist, then replace and turn the UV light back on.
Remove the towels from the tub surround and, with your gloves on, wring out any excess liquid. Discard the towels in a trash bag.
Mix 1 tsp hand dishwashing soap in 1/2 gallon warm water. Wet a clean cloth with the soapy solution and use it to wash your newly whitened tub surround. The soapy solution will remove the hydrogen peroxide and laundry booster solution from the plastic.
Rinse your tub surround with cool water, then dry with a clean cloth.
Smaller yellowed plastic pieces and items can be whitened in the same way by placing the items in the bucket with the peroxide mixture and allowing them to soak.
Keep children and pets out of the bathroom during this process as they can be harmed by the peroxide or UV light. Wear rubber gloves and safety goggles to protect yourself from chemicals and UV light.