You love the abundance of light the fluorescent lighting fixture bestows on the room, but you're not too wild about the plastic cover that has become a dingy shade of yellow. Some white plastic fixture covers are comprised of a mixture of chemicals designed to be heat-resistant and flame-retardant. The result, however, is that these plastics yellow with age, heat or prolonged exposure to light. While there is no harm to you or your loved ones from a yellowed plastic cover, the unsightly shade may offend your design senses. So gather a few household items and try to restore the cover to its once-pristine whiteness.

1. Turn the light switch to the off position.
2. Remove the light cover carefully. If the light fixture is on the ceiling, you may need to climb on a stepladder or taller ladder to do this safely. If the cover is held in place with screws, place the screws in a small juice glass so they will be easy to find and won't roll away.
3. Take your materials outside and choose a sunny spot in your yard or on your patio.
4. Put on goggles to protect your eyes and pull on gloves to protect your hands.
5. Fill a large bucket with hydrogen peroxide, leaving about 5 to 6 inches of space from the top of the bucket, advises How to Clean Stuff. If your light fixture cover is too large for a bucket, use a child's hard-plastic swimming pool to soak the cover, which will obviously require a lot more hydrogen peroxide. You can add the peroxide to water, but it may take the peroxide longer to restore the white color.
6. Add about 1/4 teaspoon of an Oxy-boosting detergent for every gallon of peroxide used.
7. Immerse the yellowed plastic light cover into the solution and allow it to soak in the sun for 3 to 6 hours. If it's not possible to submerge the entire cover in the solution, turn the cover over midway through the soaking time. At the end of the allotted time, put your gloves and goggles back on and pull the cover out to determine if it's restored to its original color. If nooks and crannies are still yellowed, submerge the cover again until it's the desired shade of white.Note: According to Odd Experiments, you can also use UV-LED lights.
8. Rinse the cover and bucket with cool water from a garden hose.
9. Wash the light fixture cover and bucket with water and a few drops of liquid dish soap. Rinse them until the water runs clear.
10. Dry the cover thoroughly with a lint-free cloth and replace it over the lights.