How do you treat plastic on durable goods that has turned from white or beige to yellow?

Answer 1

Let is stay in some bleach for some time. But don't use too much! Light (UV), ozone, or other things can attack the plastic over time. Some plastics (and there are a many types of plastic) are more prone to attack than others. Plastic resists a lot of changes, but time and a given type of attack may result in the change described. Most often, the change of color is a side effect of a chemical change that the plastic has undergone as it has aged. Often times, there isn't any "fix" for the problem.

Answer 2

To treat plastic that has yellowed, try cleaning it with a mixture of baking soda and water or with a solution of white vinegar and water. You can also try applying a paste of hydrogen peroxide and cream of tartar, then let it sit in the sun for a few hours before rinsing off. If these methods don't work, consider using a specialized plastic restoration product.