Retro Bright Science and Philosophy
If you hang around the computer restoration world, pretty quickly, you will hear about Retro Bright. Retro Bright is a process of bleaching old, yellowed plastic back to its original or near-original color. The yellowing in old plastic happens due to a chemical reaction in ABS plastic to heat and light. I won’t attempt to explain the chemistry, and thankfully I don’t have to because there is an excellent paper on how and why it happens at the link.
https://hackaday.com/wp-content/uploads/2021/01/The-Retrobright-Mystery.pdf
Some old computer plastics are affected more than others. In my experience, the worst are Apple II’s, Osbornes, and Atari’s, which change to a horrible yellow cooler.
Here is photo of before and after photos of my Osborne I plastic case.
Other systems like the Compaq Computers use different ABS formulas for the keyboard, which can look spectacularly bad!
There is some debate online if you ‘should’ Retro Bright parts. The arguments against it seem to fall into three camps.
the computer/part is old, and it should be respected for its patina.
Retro Bright makes the plastic more brittle
It won’t last anyway and will come back with time.
Personally, I don’t accept the patina argument as I think of patina as something more like ‘well worn .’ For instance, if the keyboard keycaps have worn down due to use, that’s patina; that’s history; that key was typed on a long time and deserves its due. By contrast, a computer could have just sat in the sun on a desk, never used, and turn yellow. Yellowing is a chemical process that happens to plastic without any use.
Some will say that Retro Bright will make the plastic more brittle. This isn’t the case, as Retro Bright should only affect the outer surface of the plastic. If the plastic has structural issues, I encourage you to read the paper however.
The third argument against Retro Bright is that the yellow color will come back anyway. Strictly speaking, this is true, but it will take decades if the computer is well cared for after restoration.
Personally, I fall in the camp of returning the functionality and appearance as close to the original as possible. I believe that gives service to how the designers of computers and people who loved the computer remember it. It also makes the machines more approachable to younger people who never initially saw them. An excellent example of visual differences can be found in my Osborne I writeup and my Compaq Portable I writeup.
When I started restoring computers, I found it helpful to write down my Restoration Philosophy. It appears at the top of the site.
In my second post, I’ll describe how I do Retro Bright. I have found tried and true methods and absolutely destructive methods that have ruined parts!