[Coco] Possible remedy for old yellow

[Robert Gault]

Bob wrote:

> So I was looking at this old yellowing plastic and it struck me. How about some
> whitening toothpaste? I would think it would be perfect for the job, maybe even
> help preserve the plastic...? Anyone tried this already?
> 
> OTOH, I have some athletic shoe cleaning gel in a brush/bottle that did a
> pretty good job itself. I did the top half of my CoCo3P case with it and it's
> noticeably whiter than the bottom half now, maybe not quite as white as new. It
> was the least yellowed 3 case I had, except the really white one I have boxed
> up... didn't want to hack that case.
> 
> Now my curiosity's piqued though, I'll have get some of that toothpaste and
> test it on some severely yellowed equipment.
> 
> Bob
> 
> 
> 

Speaking as a chemist and knowing something about plastics, the 
yellowing is usually caused by the oxidation of the UV and anti-oxidant 
inhibitors in the top layer of the plastic exposed to air and light. If 
the whitener is a bleach (ie. oxidizer), it usually make things worse.

If the yellowing was caused by deposition of dirt on the plastic, then a 
bleach or even a mild abrasive would clean things up.

Your tooth paste uses peroxides as a whitening agent. They could just 
accelerate whatever damage caused yellowing in the first place.

Since I don't know what happened to your cases, they may indeed clean 
up. Prudence would caution testing on small non visible portions of the 
case.