Restoration Help


I just read about this today. IIRC, there have been inquiries about how to clean old calcs in the past. Perhaps this will help a few of you:


A friend of mine used this on a junky HP21 of mine while he was doing his Vic-20 and I am impressed with the results.

My HP21 was nowhere as discoloured as his Vic-20, but the difference is significant.

I have photos if anyone is interested.


Here are the images I have at present.

Tim's Vic-20 prior to Retr0brite. This had been stored by a previous owner inverted, on a desk in the sun with stuff piled on it. It looks dirty, but this is actually yellowing of the plastic.

I delivered the HP21 to Tim a couple of hours after he had started his Vic-20 case "cooking". His case is partially done here.

He tool a close-up of the HP21 to show the foam on it. We have a bloody great hole in our ozone layer here, so this probably works better/faster than for northern hemisphere people.

Tim only gave them 3 or 4 hours rather than the all day that is recommended. He used a 6% H2O2.

Here are 2 HP21s. They both looked pretty much the same colour previously. The one on the left is now almost completely un-yellow.

I might try a similar trick on the keys of this HP21. They're not that yellowed, but it would be valuable to know if the keys will be affected. This HP21 has a number of serious cosmetic problems already, so it won't be a huge loss for me if it goes pear shaped.


What effect did it have on the feet?


It wasn't put on the feet. The stuff is a gel or a foam and can be applied pretty much where you want to put it.

If this calculator were a good one I would have taken the other feet off, or masked them with something. (you may be able to see a masked label on the Vic-20)

Maybe I'll subject the feet (and other parts -- e.g. metal parts) to this stuff to see what happens.

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