De-yellowing results

Tothwolf tothwolf at
Fri Aug 28 12:22:13 CDT 2015

On Fri, 28 Aug 2015, Ali wrote:

>> Ah! That explains my lack of results. I soaked the keys for five or six 
>> hours. They got clean, but didn't change color very much. Sounds like I 
>> pulled them out too soon. Several days, you say?
> Has anyone tried a glass/plexi-glass bath w/ UV lights? It might get 
> expensive if you want UV lights that are dimmable (to control strength) 
> but UV lights and ballasts are not that expensive. A simple timer and 
> maybe a reflective surface on the enclosure and you are good to go. Then 
> real experiments can be done by varying exposure time and concentration 
> of the solution to see if there is a happy medium. Problem is you need 
> someone with lots of yellowed parts that they don't mind experimenting 
> on/ruining in the process.

Glass blocks UV light. This is why EPROMS were made with quartz windows 
even though glass would have been much cheaper. Regular acrylic plastic 
will block UV as well, but special types are available that allow 
transmission of UV (such as for sun room roof panels and tanning beds).

Keep in mind also that short wave UV-C (such as a germicidal lamp) is 
dangerous to work around, which is why devices such as EPROM erasers 
generally have a mechanical interlock to disable the lamp when open. UV-A 
(blacklight) is much safer, and would probably give about the same results 
as having something out in the sun (UV-C is blocked by the atmosphere 
while UV-A isn't).

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