Headlight polishing
 

I'm aware this subject has come up many times, but have two questions -



There has been an argument as to whether the headlight plastic lens had a protective coating from new. Having just used the 3M kit to clean them it appears there is no coating, unless it was polished off before I bought the car. Can one of the knowlegable confirm one way or the other.


Secondly, having polished the plactic lens, is it recommended to coat them with a protective coating, such as the "Glass Polish Surface Sealant Easy Clean Coating" recommended to buy from Amazon when getting the 3M kit.

Clean them well with panel wipe and coat with gloss clear coat.

I agree, except..


I recently carried out some experiments with a donated lens. I abraded it down to what I thought was the polycarbonate, sprayed it with the gloss clear coat and it went misty. My assumption was it had reacted with the original coating. Not knowing how thick the lens material might be, I had been too wary of abrading it.



My MKII when I have refaced them and this lens when I had refaced it, both had visible marks in the lenses, which I had attributed to marks on the inner surfaces - I was wrong, I think the marks were the remnants of the old coating.



I tried again on the same lens, a bit more enthusiastic, with 100 grit paper, then finished with finer and finer grits, finally polishing with Autosol. I sprayed it again, this time it ended up perfectly clear, but showed signs of what looked like cracks in the coating. I'm thinking now, that might be due to doing the spraying with the lens too warm in the sun?


I have left it out in the weather since then, deliberately to catch the sun, but there has been no deterioration at all. I'm reasonably happy to now tackle my MKII's headlight with the same process.

From the replies so far I'll not coat the polished lenses until after it has passed the mot.

So Harry thinks there was a coating on the lens originally. Certainly no sign of it when I worked on mine, the platic reacted exactly as the 3M instructions.

is there one make you recommend?

macafee2

Polycarbonate degrades under ultra violet light, so wherever it's used to make items that will get a lot of sunlight, it's protected with a stabiliser. The stabiliser is a compound that readily absorbs UV with little apparent effect. The stabiliser may be mixed into the molten polycarbonate prior to moulding or extrusion (eg roofing sheets) or applied as a separate layer, for example by spraying on. Headlamps are coated like this and the stabliser prevents UV degrading/embrittling the lens. The layer is sacrificial and eventually becomes itself degraded. That's what you abrade away during the headlamp treatment. The yellow layer can sometimes be seen quite distinctly during the abrading process. If the stabiliser isn't replaced, the lens itself will begin degrading immediately. In my experience, a re-polished but uncoated lens will become cloudy in 24 - 36 months with the car parked pernanently outside. UV stabiliser treatments have got a lot cheaper in recent months. I'd recommend anything that states 'UV' in the name or the information on it. Those finishing wipes that applies a film from a moist tissue will last from a few days to a few weeks at best.


TC

There are supposed Special Lens coating sprays out there ,


whether they are just laquer err.. pass ..

or the other option is to wrap the lenes with clear UV protection film.

C.

I polished the headlights on the CDT earlier this year using the RainX kit. The UV coating in the kit is a liquid which is sprayed on and then wiped. I don't expect that it will last more than a year or two but given how it is applied that really is not the end of the world.

My intention is to lightly clean the lenses using the compound in the kit every year and reapply the UV coating at the beginning of each summer. This should take no more than 15 minutes.

I reconditioned my lamps a couple of years ago and they looked like new. However, I didn't use a hard coat protection so they're now fogged over. I'll have to buff them up again, but this time I'll coat them with a clear/hard coat UV protectant. I've just received this today -


https://www.mediafire.com/convkey/01...ds2fcjjh6g.jpg


- from eBay: https://www.ebay.co.uk/itm/E-TECH-Re...72.m2749.l2649

Wipe-ons are only temporary. The only way is a hard laquer coating with UV inhibitors.

TC

I've tried odd things even those paint protector coatings like the 2 part Diamond Brite, but doesn't last :duh: