If you work on old radios, electronics is only one of the skills you need. The other is wood or metal working to restore the cabinets and chassis. However, more recent electronics have plastic and old plastic tends to turn yellow. [Odd Experiments] shows how to whiten plastic using a UV light source, aluminum foil, and hydrogen peroxide. Generally, ABS is the plastic at fault, especially those mixed with bromine as a fire retardant. You can see the results in the video below.

Note the peroxide in use was 12% — much stronger than what’s probably in your medicine cabinet. That’s usually only 3% solution, although you can get different strengths including some over 30% if you shop. However, if you search you’ll find that people have used 12%, 6%, and even 3% successfully, although we’d imagine it takes more time with 3%.

You’ll also need some patience. Best results apparently occur in 24 to 48 hours. We’ve seen other people use small amounts of TAED (tetraacetylethylenediamine; a laundry additive) to accelerate the process. The TAED mixes with hydrogen peroxide to form peroxyacetic acid.

We’ve also seen people do this with hydrogen peroxide-based hair bleaching creams that they can apply like a paste. We can’t promise any of this doesn’t weaken the plastic, but it does seem like it works, for the most part.

We have looked at this process before, and that post explains some of the chemistry occurring. If you want to restore old knobs, maybe try Neosporin.