Headlight restore - 1) pitting 2) to lacquer or not?

I did my video on sanding mine some time back. No degradation so far.


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I can't understand all the discussion about lacquer. Car's colour coats are flatted and then lacquered, and, generally, that lacquer lasts for years. Why would headlights be any different?
Mac.
 
I've had good results using a machine polisher with G3 cutting compound. Never used wet and dry, seems slot of work for the same finish. But then I guess it is a proper polisher and not the tiny ones you see people use.
 
I can't understand all the discussion about lacquer. Car's colour coats are flatted and then lacquered, and, generally, that lacquer lasts for years. Why would headlights be any different?
Mac.
I kind of understand what you mean but my very limited knowledge kind of tells me that the lacquer used in the paint shops is nothing like the stuff we can buy on the shelf at our local car accessories shop, the stuff they use would probably cost us mere mortals a small fortune for a litre and we could not apply it in the conditions that they do.
 
I kind of understand what you mean but my very limited knowledge kind of tells me that the lacquer used in the paint shops is nothing like the stuff we can buy on the shelf at our local car accessories shop, the stuff they use would probably cost us mere mortals a small fortune for a litre and we could not apply it in the conditions that they do.
I've used 2k lacquers, yes they are expensive but some paint shops can mix it in an aerosol for around £15. It doesn't cure until it hits the atmosphere so you dont get a can of hardened lacquer (if you leave it a while it will!) However the headlights being polycarb and having light from both the bulb and ultraviolet clouds the plastic. We sometimes use 6mm polycarb in race windscreens, but they are sent away when being made to have a fine almost glass like coating applied so wipers run smoothly and the material does not cloud. Rather expensive as well - a polycarb screen with anti fog was IIRC £900.... Getting back to the point, I'm due to polish my lights soon so will see if there's any clear knocking about and give it a coat.
 
Lacquer is seen as protection, but this is only part of the story. The sanding process, using finer and finer grades of wet'n dry paper is to remove the surface damage, scratches, crazing and milkyness, not to achieve a clear "as new" finish. After sanding, the surface should be smooth, but not too smooth, like the colour coat on flatted paintwork. This flatted surface provides the key for the lacquer to bond to the polycarbonate. The lacquer will turn the flatted surface clear, just as it transforms the flat colour coat on paintwork.
Maybe some of the problems experienced with lacquer only lasting a short time is due to the over enthusiasm at the sanding stage, to achieve a clear finish before lacquering, rather than preparing the surface for lacquerIng.
If you can find a local body shop who will do it for you, I'd think that would be a good idea.
Mac.
 
I haven't read whole thread so I don't know if this has been mentioned before.

ALL headlights are clear coted from factory!

If you watch carefully during sanding, you will see and feel the difference between areas with bare plastic and coated ones.When you are sending it down, you have to sand coat completely down on whole surface. Otherwise it will do "maps" which look terrible. Also not every car has same clear coat. Some are really easy to remove (e.g. Passat 3C) and some are pain in the a** (e.g. first XC90).

Using cross hatched pattern is key feature once you use every grit only in one direction and always perpendicular to previous one. Only this way you will be able if you have sanded enough to get rid of the gauges from previous grit or not (e.g. in the first post on the right I can see this has not been done properly). Also when you are restoring headlights you have to keep in mind that defections in the plastic are not only on the surface but usually go into the plastic. Then you have to know if some defects are possible to remove or not and what the cost is (amount of removed material). Something is doable, something "propably" yes and something definitely not (you would make the plastic too thin). To judge this you have to do few pairs of headlights. For example in the first post on the left side it seems it could have been possible to sand it off or it could have been too deep ("second category").

In the laquer topic - as PlasticMac wrote. Don't over do it. Sand it to 1500 - 2000 grit max and then apply laquer. If you go crazy like 3000, 5000 or more it won't have anything to bond on and the laquer start to peel in some time...
 
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