The holiday season gave me the chance to de-yellow my Brother AX-30 following the guidelines published at Brian’s Blog-A-Ma-Jig (https://briangoo.de/2019/03/19/how-to-de-yellow-old-plastic-parts/ (link now broken) …
To summarize and greatly over-simplify, ultraviolet light destabilizes the plastic and changes it on a molecular level, resulting in yellowing. Fortunately, this process is reversible by exposing the plastic to ultraviolet light while in the presence of hydrogen peroxide.
A very yellowed keyboard cover from a donor AX-20 was the easiest part to de-yellow. A liberal coating of hydrogen peroxide cream was applied …
I then covered the exposed surface with cling film. This not only prevents the peroxide from drying out too quickly (as per Brian’s tip) but also allows you to evenly smear the peroxide cream across the surface. As Brian noted …
Make sure to wear gloves when using this stuff, and don’t get it in your eyes, you’ll regret it!
Within half an hour of being exposed to the West Australian sun (this was done on a mild summer day, temperature around 26 degrees C) I began to see a change as the plastic reverted to its original grey-beige. Another note from Brian’s original post …
By the way, you’ll notice I said “de-yellowing” instead of “whitening”. That’s because this process removes the yellow cast caused by photodegradation, it doesn’t “bleach” or “whiten” it.
On close inspection of the keyboard cover, a few smears of discolouration remained:
So I applied peroxide to the lid a second time while also tackling the left-hand side of the typewriter …
The right-hand side and then the rear of the AX-30 were tackled next.
These were not as yellowed as the donor keyboard cover, but still noticeably yellowed. I left each side/surface to bake for an hour, masking off the edges using decorators masking tape (nothing too tacky).
The results were better and quicker than I expected.
Hats off to Brian for his original post. “For he knows how to de-yellow, for he knows how to de-yellow …”
See Also: The Quick Brown Fix