I use this foam cleaner it really works great on beige computers.

https://cpc.farnell.com/pro-power-chemicals/p … osol/dp/SA01881

You spray it on and leave it for a few minutes and scrub with a damp microfibre cloth. It has made multiple old machines literally look like new. It does strip the colour off Pentium 3 badges though I've found so I now keep it away from stickers.

A magic eraser sponge is also really good for more stubborn marks, these are essential if you are restoring beige plastics.

For retro brighting I use a peroxide mousse and cover with cling film and leave in the sun for a day or 2. It will go yellow again so it's only a quick fix really. Does look amazing for a while though!

Adding to retro brighting, if the plastic parts aren’t like huge case parts, but smaller bezels, keycaps and keyboard plastics, micro computer cases etc., the best way IMO is to make a few percent strong peroxide water solution in a transparent plastic storage box so that you can submerge the part in the solution instead of using paste. It guarantees an even result and minimizes the risk of striping etc. Put the box in sunlight and you can increase sun’s effect with aluminum foil under and ”behind” the box so that maximum amount of UV is reflected to the parts.

Just putting the parts to sunlight works too, it just takes considerably longer than with peroxide. Last time I tested only using sun was with very yellowed VIC-20 case. It needed grilling for couple of days (I’d estimate 14-15 hours alltogether), but it came out very well. With peroxide couple or few hours is usually enough.

Before retro retrobrighting is extremely important that all the parts are washed and very clean or the results will be easily uneven.

CharlieFoxtrot wrote on 2026-08-06, 19:42:

Adding to retro brighting, if the plastic parts aren’t like huge case parts, but smaller bezels, keycaps and keyboard plastics, micro computer cases etc., the best way IMO is to make a few percent strong peroxide water solution in a transparent plastic storage box so that you can submerge the part in the solution instead of using paste. It guarantees an even result and minimizes the risk of striping etc. Put the box in sunlight and you can increase sun’s effect with aluminum foil under and ”behind” the box so that maximum amount of UV is reflected to the parts.

Just putting the parts to sunlight works too, it just takes considerably longer than with peroxide. Last time I tested only using sun was with very yellowed VIC-20 case. It needed grilling for couple of days (I’d estimate 14-15 hours alltogether), but it came out very well. With peroxide couple or few hours is usually enough.

Before retro retrobrighting is extremely important that all the parts are washed and very clean or the results will be easily uneven.

There is a newer version of retrobrighting for large parts called vaporbrighting, it uses a lot less hydrogen peroxide than submersion, by new I mean from 4 years ago

I don’t think I want to try retro bright just yet as I hear it does NOT last long.
The old beige computers I have are not that bad. They just look a little yellow.
I want to try some type of cleaner or foam that is available in the USA
I can buy from amazon or other online store.

Intel486dx33 wrote on 2026-08-07, 15:35:

I don’t think I want to try retro bright just yet as I hear it does NOT last long. The old beige computers I have are not that b […]
Show full quote

I don’t think I want to try retro bright just yet as I hear it does NOT last long.
The old beige computers I have are not that bad. They just look a little yellow.
I want to try some type of cleaner or foam that is available in the USA
I can buy from amazon or other online store.

i used mr clean sponges then afteward i use clear varnish on it so it keeps it grey color

I was hoping for some type of spray or liquid that I could just
Wipe on with a rag or sponge and it would clean all the dirt
And stains on the case.
I don’t want to take the computers apart and retro bright them
I just want to remove all the yellowing.
You would think there would be a liquid or jell to do this ?

Intel486dx33 wrote on 2026-08-07, 23:45:

I was hoping for some type of spray or liquid that I could just Wipe on with a rag or sponge and it would clean all the dirt And […]
Show full quote

I was hoping for some type of spray or liquid that I could just
Wipe on with a rag or sponge and it would clean all the dirt
And stains on the case.
I don’t want to take the computers apart and retro bright them
I just want to remove all the yellowing.
You would think there would be a liquid or jell to do this ?

You can't wipe off the yellowing - it's inside the plastic not on the surface. The chemistry of the plastic changes over time, and hydrogen peroxide with exposure to UV is the chemical which removes the colouring without removing any material (If only for a couple of years).

You can buy off the shelf sprays with the right chemicals, but you are still supposed to disassemble the plastics and leave them in the sun (for UV exposure) with the spray applied.

The one exception to this I have come across if if the device was in an environment with a heavy smoker, nicotine stains can look very similar to typical yellowing and can be removed with regular cleaning.But if that's the case you can really smell it.

I mostly use just Dawn Powerwash and warm water these days. It doesn't harm the plastic even if you scrub with intensity.

Magic erasers work great for painted metal cases. Only in extreme cases do I use it on plastic and very lightly, lest you risk making a shiny smooth spot where you just scrubbed.

The only ways to restore a yellowed case that I know of are:

1) Retro-brighting with hydrogen peroxide. But as others have noted this is a temporary solution. I have a retro-brighted case that gradually became yellow again after about a year.

2) Painting the case. I've only seen examples with spray paint, though airbrushing would be preferred because you can apply finer coats. Painting a case will change its texture and feel.

3) Recreating the plastic case parts with modern plastic techniques (e.g. 3D printing). This is the most labor intensive and expensive option since it involves 3D modeling and a fairly large 3D printer to accommodate the size of parts needed.

Alternatively, you can always learn to love the yellow plastic and not worry about it.