Date   : Wed, 01 Nov 2006 12:07:31 -0000
From   : faz@... (neil f)
Subject: de-yellowing cases?

 

> -----Original Message-----
> From: bbc-micro-bounces+faz=nildram.co.uk@... 
> [mailto:bbc-micro-bounces+faz=nildram.co.uk@...
> ] On Behalf Of Charlie.Robson@...
> Sent: Wednesday, November 01, 2006 11:03 AM
> To: bbc-micro@...
> Subject: [BBC-Micro] de-yellowing cases?
> 
> 
> Hi all.
> 
> Has anyone thought about, attempted, suceeded/failed in 
> de-yellowing a beeb case?
> 
> I'm guessing the answer is somewhere between 'age is a 
> terrible thing' and 'how long is a piece of string'.
> 
> Is the yellowing an unavoidable part of the beeb aging 
> process? Does it depend on environment? Or a bit in the
middle?
> 
> <big hug>
> 
> Charlie

It's largely a function of exposure to light (UV). Beebs that
have had something parked on them for a long period (year or
more) will show a lighter 'shadow' where the light was masked
out. Beebs left in strong sunlight (windowsills etc) will yellow
deeply compared to those kept under a cover. Boxed Beebs kept in
the dark yellow only imperceptibly. 

Most (all?) plastics exhibit this yellowing after prolonged
exposure to UV. The yellowing is likely to be down at the
molecular level so I don't think you can remove it chemically,
only by scouring off the top surface - which will obviously
change the texture of the plastic too. I suspect if anyone had
found a solution we'd all have heard of it by now.

-Neil F.