Place the plastic pieces under the sun and leave them there for at least a day. It's the UV rays from the sun that in combination with the hydrogen peroxyde will make yellowed plastic white again.
Fortunately, you can easily remove oxidation with sandpaper, vinegar, or a bleach solution. Plastic that has faded to a yellow or brown color was made with bromine, which causes the plastic to change color over time. However, you can reverse bromine discoloration with hydrogen peroxide.
In the presence of UV light, oxygen in the atmosphere produces carbonyl groups. This changes the color to yellow-brown and the plastic begins to flake away until it becomes useless. Gas fading in polyethylene films and articles is a common problem.
Why does your once white clock face, storage box, old video game console, or white appliances turn yellow? Well, it's because of excess UV light exposure. The more exposed plastic is to UV light, the quicker it changes color. However, the change of color does not happen straight away – it will take a while to change.
White vinegar works wonders on plastic similarly to bleach, without it being as harmful. Mix 1 part white vinegar with 1 part water before pouring the mixture into or onto your plastic. Let the plastic sit with the white vinegar for a couple of hours before rinsing it clean with soap and water.
A mixture of five cups of vinegar and one gallon of hot water can be applied via a spray bottle onto the affected area. Long-handled, soft-bristled cleaning brushes help to remove the oxidation. Continuing this manner in small sections works best so the solution does not dry out.
Heat brings the oils in the plastic up to the surface. It's temporary and will eventually fade again. A new heat cycle will do it again until there are no oils left in the plastic. IMO Solution Finish is the best way to restore plastic.
The reversibility of the discoloration chemistry has been “demonstrated” by placing the discolored plastic in UV-rich light (e.g. sunlight), which “bleaches” out the color by causing the quinone to go “away;” however, this reaction is not truly reversible.
Yellowed Plastic Containers
All it takes is a little water mixed with baking soda to create a paste. Apply this paste to the container and let it sit for a couple of hours, before spritzing with lemon juice, washing with warm water, and drying as normal.
UV radiation causes stabilizing agents in the plastic to form so called free radicals which cause the yellowing. This UV light is present in sunlight but also in fluorescent light. Hydrogen peroxide binds to these free radicals, thus reversing the yellowing of the plastic.
Food dye commonly stains plastic that are left unrinsed. Coffee, tea, juice, soda, tomato sauce and tomato paste stains are the leading causes for discoloration.
Measure a quarter cup of baking soda, add roughly 50ml of warm water and proceed to mix until it is a paste. Then, with a wet towel, wipe the seat and apply the paste to the stained surfaces.
If you have some old, faded electronics or other plastic gadgets in your house, you can make them look great again with just a dab of Vaseline.
To reverse some or all of this aging plastic can either be submerged in Hydrogen Peroxide liquid or coated with paste and exposed to ultraviolet light. The progression of color restoration over a 48-hour treatment in 12% liquid.
Whitening process. The reverse process uses commonly available 6% or 12% hydrogen peroxide and UV light as catalyst (can be common UVA bulb or even simple sunlight) to activate the whitening reaction. Ultraviolet light bombarding hydrogen peroxide generate very active hydroxyl and restore the original color.
Luckily, bringing out the plastic's natural luster is easily done. By rubbing olive oil or using a heat gun on the faded area, you can help your plastic look as good as new. And, if all else fails, you can always use black spray paint to give your plastic a sleek shine again.
The plastic and glass surfaces on most small kitchen appliances, such as blenders, coffee makers, and toasters, are safe to clean with vinegar, but you want to avoid any rubber parts or metal that vinegar can corrode. This includes stainless steel.
Avoid using abrasive cleanser that may scratch the plastic. Use a tub/tile/sink cleaner; nonabrasive, all-purpose cleaner; or a paste of baking soda and water. Apply the cleaner to the surface or on a damp sponge and rub gently.
The easiest and safest method to make whites white again is to use a solution of oxygen-based bleach and warm water. It can be used safely on almost all types of fabric. You can also make whites white again by using the ultraviolet rays of the sun or using laundry bluing, baking soda, vinegar, or chlorine bleach.