35% is quite strong, so you can get away with small amounts. It's hard to say how much, because it also depends on the amount of yellowing, the amount of uv light/sun and how long you want to wait for the process to complete.

I mostly work with 6 or 12% and then using maybe 100ml on 1 liter? Might be even less.

Hezus wrote on 2023-02-20, 21:50:

35% is quite strong, so you can get away with small amounts. It's hard to say how much, because it also depends on the amount of yellowing, the amount of uv light/sun and how long you want to wait for the process to complete.

I mostly work with 6 or 12% and then using maybe 100ml on 1 liter? Might be even less.

Thanks for the reply. So can hydrogen peroxide damage the plastic in higher amounts?

dominusprog wrote on 2023-02-20, 22:14:

Hezus wrote on 2023-02-20, 21:50:

35% is quite strong, so you can get away with small amounts. It's hard to say how much, because it also depends on the amount of yellowing, the amount of uv light/sun and how long you want to wait for the process to complete.

I mostly work with 6 or 12% and then using maybe 100ml on 1 liter? Might be even less.

Thanks for the reply. So can hydrogen peroxide damage the plastic in higher amounts?

Yes, it will bleach them in varying amounts depending on the different types of plastic, if it's done by submersion. If you really must retrobright something, I'd recommend RMC Neil's demonstration of the vapor retrobrighting method that someone else discovered, check "RMC Amiga 1000 trash to treasure" on YouTube, the safest method so far (contactless with the plastic), and most economical as well.

It's been a recurring fact (that I too experienced in all my numerous jobs) that all types of plastic eventually re-yellow after six months up to a year and a half, even when stored and kept with no direct sunlight or heat, or in total darkness. However it re-yellows to lighter tones than before, and balances the shade throughout, erasing different patches of yellow along the surface. So depending on the piece, in these specific cases it may be worth it. But of course feel free to experiment if that's what you really want.

Personally, for everything else, don't bother. Between money, time and effort the results after some time just aren't worth it. Clean your stuff, keep it from direct sunlight and enjoy it

It's very pleasing to see the results of retrobright in videos and also when you start doing it yourself. However, as mentioned above: it's not a permanent solution. The yellowing will come back eventually. Going through the process over and over to keep your hardware looking fresh gets tiresome after a while, especially if you have a lot of stuff. There's also no telling what the peroxide will do to the plastics over long periods of time.

I've actually resorted to just painting instead of retrobrite. I won't paint things I like to keep in original state but it works well for more generic items that you might not care for as much.

Thanks for the info, much appreciated. I'll add two part of water to make it 12% and try both regular and vapor methods.

There are rumors that there is no need for any chemicals at all. It is enough to place your yellowed plastic case ... under direct sunlight. Yes, it sounds stupid, but there are evidences that sun the same time causes yellowing for new plastic cases and retrobrights already yellowed ones. The difference between the conventional method with chemicals and this one is the time it takes. The latter one takes way much longer.

ThinkpadIL wrote on 2023-02-22, 15:36:

There are rumors that there is no need for any chemicals at all. It is enough to place your yellowed plastic case ... under direct sunlight. Yes, it sounds stupid, but there are evidences that sun the same time causes yellowing for new plastic cases and retrobrights already yellowed ones. The difference between the conventional method with chemicals and this one is the time it takes. The latter one takes way much longer.

Well, as far as I know, the UV light only provides the energy for molecules to break and lose their hydrogen atoms.