Restore HP-29C yellowed case

[Graham D. Wilson]

Does anyone have actual experience restoring a Woodstock case to its original cream colour and be able tell me how they did it? The plastic housing of my 29C has become quite yellow over time, despite being stored away from UV light.

Thanks
Graham

[PANAMATIK]

See this thread: http://www.hpmuseum.org/forum/thread-4211.html

You have to clean the case very carefully and rinse with distilled water. The main problem with bleaching is that there can occur irregular patterns with different brightness. Don't bleach too long, this inceases the possibility of irregulartity. Sunlight is not necessary, but it accelerates the process.

Bernhard

[Dave Frederickson]

Mr Clean Magic Eraser, an alternative to Retr0brite.

https://groups.io/g/hpseries80/wiki/Upgr...oam-Sponge

[BobVA]

Or you might pick up an inexpensive "parts or repair" Woodstock and swap the shells.

[Kees Bouw]

Hi,

Take a look at http://www.retr0bright.com. Looks spectacular, I don't have any experience myself though. I don't mind seeing that a calculator has aged, it's like getting grey hair.

Kees.

[Graham D. Wilson]

Thanks everyone. I'll proceed very carefully, if at all, to try and restore the case of my most favourite HP calculator, which works as well as the day it was bought in 1979.

Maybe yellowing plastic was a reason why HP chose black and brown cases for the calculators that came after the Woodstocks...