Car headlamp lens polishing

Harry Bloomfield formulated the question :

You need a UV protective coating on them once you've cleaned them but so far I'm not sure what to use or which is the best, so I'll be watching this thread with interest.

Toothpaste is good, followed by a silicone wax. If you use stick on 'deflectors' for driving in Europe, the glue can damage the plastic, I use protectors if possible and stick the defectors on those. Clean the glue residue off ASAP and rise with water.

The lacquer probably isn't a good idea, the solvent may damage the plastic.

My CRV had protectors on, one was 'nicked' (why one?) and the lens under them are as good as new except for a bit near the top, after 11 years. My MX5, new in 1999, has protectors, and its lenses are as good as new under them.

I believe they're polycarbonate, yes. As to a solution to the yellowing/hazing, don't know, sorry.

I used clear nail varnish on one set of headlamps. Worked for a couple of years, then I replaced the housings with new. Cost was minimal.

Have you checked the usual suspects like Google and Ebay for a polishing kit? I've seen them on sale somewhere, but luckily have never needed one.

The thing I'd try first is good 'ol Brasso. Or Autosol.

I am just waiting for the gf to smash the OS headlamp into something so that I have an excuse to swap it and make it look as good as the NS one that she smashed last week.

It was not her fault - even though the fence post that broke the headlight was there 10 years before she was born it was still not her fault as it did not give way.

The same fencepost also gave her cars OS rear cluster lights a good kicking last year.

I used toothpaste. It got the car through the MOT. It is a silly problem which I could do without. I think new replacements would have been quite expensive for a car nearly 14 tears old at the time.

Also - If I have a nice newish car - how can I prevent - or delay this dererioration?

Dave Plowman (News) explained :

Polishing them up, to a clear finish is not the issue, I have done that

- the problem is to find something UV proof to spray on after polishing, to delay it happening again.

Suntan cream ;-)

One part of this appears to be designed for the job, But what chemicals are involved I have no idea.

Presumably it takes a few years to happen? Or is there some form of chemical change which means it will happen more quickly a second time if polished clear?

I've seen a similar thing with car paint. Goes dull, and a compound and polish makes it look good again - but only for a short while.

New headlights have a uv protecting layer. Polished ones don't.

NT

I think the lenses just age just like those corrugated sheets do. A friend seems to get through Citroen ones on a hearly basis. I find it hard to believe they cannot make a material which lasts without going milky yellow or brittle in the normal climate. I have to conclude that its just that they don't want to make them last. Brian

Harry Bloomfield presented the following explanation :

I know Harry's asking about how to keep them bright after the restoration and so am I, but to take the restoration aspect first, it happens because of oxidisation. If the oxidisation is extremely light then you may just get away with the toothpaste method but it really does only work when the problem is very slight.

Most cases of oxidisation will require something much better than toothpaste and the 3M Headlight Restoration Kit is considered one of the best

I've got that kit but I haven't done the job yet because I haven't so far found a suitable UV protector spray to coat them with afterwards. There is absolutely no point in putting the effort in to get great results if you don't coat them with a UV protector afterwards because in a month or two they'll just be as bad again.

When the lens is manufactured a protective layer is built in at the factory and it could take 10 years or more for it to break down and become yellowed. When you polish out the oxidisation you're basically removing the factory protective layer so you need something to replace it after restoration. Most of the YouTube vids I've watched about the process are american and we can't get hold of the UV protector(s) I've seen them using, here in the UK as far as I know.

So, basically we're still looking for that elusive spray.

Pete Zahut has brought this to us :

Exactly right, which is where I am at, at the moment. My lens had not yellowed, the had become slightly opaque - wet a finger and dab it on the lens and it would show clear.

Pete Zahut wrote on 08/08/2017 :

A bit of research seems to suggest that 2K UV proof top coat is the best stuff to use. One manufacturer of such a spray, even advertises it for that purpose.

This

I have used Meguiars one step before. They do a two step kit which includes a UV protection spray:

I havent used it myself.

Alan