Ive had my commodore amiga 500 computer since 1989 and when i purchased it, it was a crisp clean cream color. But after getting it out of the attic after a few years, it appeared to have completely changed color. It was now a more of a patchy yellow color that looked quite discusting. The keyboard was even worse. It now appeared to be brown. Yuck!!! Ive always looked after my computers and this not was how i expected it to look. The condition of the case looked as if it had been abused over the years and had never been cleaned.
It appears on closer inspection that its not dirty at all, but the plastic has actually darkened in color. This is due to light and heat exposure over time.
After hours of research on the internet it seems its possible to reverse this damage with something as simple as hair bleach. Yeah the kind my girlfriend puts in her hair to make it blonder. So I did some experiments….
I removed the top part of the case and coated it in a thick layer of hair bleaching peroxide. This here is the exact stuff…
So I completely covered the amigas case in it, wrapped some foil around a large tray to make it as reflective as possible and put it out in the sun for about 4 hours. Here is a picture of the case before I put the peroxide on it. As you can see it looks like shit.
So after about 4 hours I brought it in and rinsed of the peroxide so I could have a closer look to see if it worked at all.
As you can see from this next picture, there is a definite improvement. The shitty brown color is definatly beginning to fade away to reveal the original color of the plastic.
So looking that this result I am confident that another go at it with fresh peroxide and maybe a whole day in the sun, this amiga could look as good as new again.
The next part that looked awful was the keyboard.
I removed all of the keycaps for this next job because I didn’t want to get peroxide on the pcb.
So in conclusion to the question; Can whiten plastic that has yellowed? The answer is a definite YES! and its easily possible with some hair bleach and at least 4 hours of bright sunshine. After more experimentation the more time in the sun, the better the result.
For a more detailed example of restoring yellowed plastic, have a read of my Commodore 64c restoration project here