On 14/07/2019 16:40, newshound wrote:
On 14/07/2019 09:27, Spike wrote:
On 13/07/2019 20:02, Harry Bloomfield wrote:

Lots of modern car headlights have this issue. Polycarbonate absorbs
UV, which crazes the out surfaces. So surface removal works, but when
manufactured, they had some sort of UV proofing coating. That coating
eventually wears away, leaving the polycarbonate with little
protection. Fine abrasive polishing brings the clarity, but with none
of the original protection, they very quickly degrade again.

Ideally, what is needed is a DIY clear spray, which is proof against UV
to protect the polycarbonate lens once it has been restored.

I've used this stuff for many years on the appropriate parts of my
motorcycle:

https://www.amazon.co.uk/Armor-All-G.../dp/B0001OZH1C

A semi-gloss version is also available.

That looks useful, and not silly money, and claims to include a UV
filter. I think I would still worry slightly that it might "attack"
polycarbonate (in spite of saying safe on plastic).

My machine's 30 years old next year, and the plastic and rubber parts
are just fine. The headlamp lens is glass but the other lenses are
plastic and they are just as they came out of the factory. Armor-All is
I believe water-based rather than VOC'd and has the appearance of cow's
milk.

I think I might be happier with this

https://www.amazon.co.uk/3M-39173-Qu...20534429&psc=1

3M is a top company, I've done research using their materials; that
product looks OK. My personal preference is not to abrade the lens
surface but to use a UV filter/blocker and slow the deterioration.

--
Spike