In this article, it states:
In nearly every case it’s flame retardants. Although plastics can yellow in the absence of flame retardant chemicals, the chemicals accelerate the process when exposed to heat, oxygen, and ultraviolet rays.
The process of the plastic reacting with the heat, oxygen, and UV rays makes the plastic yellow. Flame retardants (very ...
Assuming the yellowing isn't caused by nicotine, if you're a smoker, usually it's because of UV light interacting with flame retardants (usually bromine) in the plastic of the device's case. UV exposure can be from sun or fluorescent lights - the yellowing plastic isn't picky about the UV source.
I'm not aware of it being solved in modern plastics.
Search the web for the term "Retrobrite" or "Retr0bright". You will also find numerous sources (including YouTube) for recipes and how-to's using OxyClean and other sodium percarbonate-based products which yield hydrogen peroxide in solution or in a paste form.
These techniques are very popular for whitening cases with the Apple ][ and Atari communities. ...
As has been mentioned already, the most common reason is flame retardants.
I've found that the easiest way to restore the original color is hydrogen peroxyde + UV light (either from the Sun or from an UV lamp).
Some time ago I restored an MSX turbo R and documented the process, including whitening the case and keyboard. Here's the link.
For the mouse ball, remove it and clean the rollers with some rubbing alcohol and a q-tip or if its really grungy, pick the crud off with your fingers first. The ball itself can usually just be wiped off with a dry cloth.
As for the yellowing of the casing that's normally a problem with the casing discolouring due to flame retardants oxidizing the plastic. ...
I used the method outlined here by Javier Rivera on my Apple IIc Plus and it worked fine. Javier does a lot of RetroBrite projects and posts a number of results to the Apple II Enthusiasts Facebook group. He also gave a presentation on methods at KansasFest 2015 and did a live session with anyone who wanted to go through the process with him.
I have used recipes from here with great success:
I used the second recipe with a high concentration hydrogen peroxide. I was able to find the high concentration hydrogen peroxide at a local co-op store marked as "food grade".
Here is that recipe:
Lorne's Variant Recipe
Lorne at Vintage Computer Forums prefers ...
Degradation may be initiated or accelerated by numerous factors
including ultra-violet light, visible light, ozone, pollutants,
manufacturing additives, oxygen, heat, or by carton storage without
As mentioned in other answers, one of those "manufacturing additives" is flame retardants.
Also, make sure the storage room is well ...
The best thing I ever found for cleaning mouse balls is denim. The texture seems to be perfect. New denim might be an issue due to the fuzzy fibres getting on the ball.
Don't use anything sharp to clean the interior plastic rollers as the scratched plastic will collect dirt more quickly and extreme scratches could cause uneven rolling.
Retr0brite will ...
No tools or fluids method, takes about a minute or two all total:
Unscrew or unclick the retaining plate on the bottom, remove the ball, then find the two or three rollers. Scratch off the accretion on each roller with your sideways fingernail, (so the roller cannot turn more than a few degrees), turning as needed to get all 360 degrees. The lint-like ...