Headlight sealing after restoration?

jhakken said:
Any thoughts on the combined usage of a paint sealant and one of the dedicated plastic UV protectants? I wondered if one could top the sealant but I have no idea about the polymer chemistry that might be involved.
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My thought is that is what the "Spar" urethanes are. They are already chock full of UV blockers because they are designed to protect wood exposed to full sun. Similarly, they are designed to keep salt water and other filth away from the wood. This is pretty much what we want for a headlight protectant too.



The main question is what kind of a bond the urethane will be able to maintain with the headlight plastic. I suspect that the best way to use these is to rough up the headlight slightly with some sandpaper, clean the dust off thoroughly by washing with water, then wiping with alcohol, and then apply the urethane. That will give the urethane some texture to hang onto, rather than the smooth, polished polycarbonate which is what most people are painting. On the flip side, it might result in bubbles at the scratch lines, which would be bad.



I also wonder how well the urethane will stand up to the temperature cycles it is going to be exposed to while it is plastered over a headlight. Only time can answer that, and the web is suspiciously silent on that point.
 
another qx4 said:
I recently restored a pair of headlights. They weren't in terrible condition but showed signs of hazing and yellowing. I used 2000 grit sand paper then SSR 2.5 with a 4" pad on a PC. It turned out great.



Now the question is... What is the best and more durable way to seal the headlights? I am sure that the headlights came with some sort of protective coating which deteriorated over time. I'm looking for more than just a simple LSP one would use on paint because it doesn't seem like it would do an adequate job on plastic headlights.... Or does it?
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You're right. When the headlight was manufactured, a protective coating was sprayed on then baked or UV cured. The coating has two purposes;



Protect the polycarbonate from ultra violet, and seal the poly from moisture.



Polycarbonate is very porous and easily damaged by UV. It is this protective coating that breaks down causing yellowing and fogging.



We use a chemical stripper which removes the damaged material (mostly silicone) then apply a new protective coating (very similar to the original).



We only sand about 20% of the time and only for retail or used car sales. Most of our work is commercial in nature and the customer does not want or need to pay extra for a crystal clear restoration.



Without replacing the removed damaged coating, the exposed polycarbonate will discolor and is not easily repairable. Personally, I wouldn't do any restoration without putting a protective coating back on because it won't last. We warrant our restorations for 2 years.



Hope this helps.



Ray6
 
after reading the link about Spar Urethane mixed with Mineral Spiritrs, i was curious... can these be premixed in a bottle and stored indefinitely? Im sure both come in larger containers that may make carrying them around, or mixing them on the spot difficult. it would be much easier to premix a small container of it and keep it with you... especialy if you're mobile.



i dont see that it would have any negative side effects, but perhaps someone with a bit more knowledge on those products would know better.



also, they repeatedly talk about a "blue shop towel". are these the blue sheets that come on a roll, like regular paper towels?
 
Aekon said:
after reading the link about Spar Urethane mixed with Mineral Spiritrs, i was curious... can these be premixed in a bottle and stored indefinitely? Im sure both come in larger containers that may make carrying them around, or mixing them on the spot difficult. it would be much easier to premix a small container of it and keep it with you... especialy if you're mobile.
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I would imagine it would keep for quite a while in a small metal paint can - no light gets in, it seals well, and there is no plastic inside that could be dissolved by the mineral spirits. If you could fill the empty space with nitrogen it would probably last forever in that, but since it will almost certainly have air in it instead, fill it most of the way up to reduce the amount of oxygen present in the can.
 
ray6 said:
You're right. When the headlight was manufactured, a protective coating was sprayed on then baked or UV cured. The coating has two purposes;



Protect the polycarbonate from ultra violet, and seal the poly from moisture.



Polycarbonate is very porous and easily damaged by UV. It is this protective coating that breaks down causing yellowing and fogging.



We use a chemical stripper which removes the damaged material (mostly silicone) then apply a new protective coating (very similar to the original).



We only sand about 20% of the time and only for retail or used car sales. Most of our work is commercial in nature and the customer does not want or need to pay extra for a crystal clear restoration.



Without replacing the removed damaged coating, the exposed polycarbonate will discolor and is not easily repairable. Personally, I wouldn't do any restoration without putting a protective coating back on because it won't last. We warrant our restorations for 2 years.



Hope this helps.



Ray6
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Good info Ray, but a headlight reconditioning company I do business with (Northern Lights in Michigan)says that when doing light resoration of a lens it's best to use several grades of sandpaper to remove as much of the damaged lens material away before just lightly final buffing and recoating. They say excess buffing will cause crazing and overheating of the platic which isn't advised. They mentioned that this OEM UV coating is very thin & soft (~1 mil) and most of time when techs buff lights they end up removing this coating and prematurely decreasing the life of the light - i.e ruining it.



As an Auto Appraiser for an Insurance company, any time I see a light that's damaged I either replace it or send it to Northern Lights to have them restore it back to OEM specs. If I write or allow a shop to buff a light and it fails prematurely, it would fall back on me for allowing an improper repair.
 
The GE products now seem to come from a company called Momentive, with a really slow web site. This document describes in general terms their hardcoat

products, including those for headlights:



http://www.momentive.com/momentiveI...ta Sheets/Hardcoat Selector Guide MB.indd.pdf



For the heat cured products the best seems to be AS4700, with AS4000 and SHC4002 not nearly as strong but about equal to each other. Also equivalent to these two are two UV cured products: PHC857 and UVHC3000. THis is from the chart on the second page.



The UV ones can go right on the plastic, but the thermal ones need a primer, for instance:



Momentive Performance Materials



The primer seems to be pretty easy to apply. The hard coat is a lot pickier. The thermally cured ones need 10 - 60 minutes at 130C under carefully controlled humidity and very clean conditions. The UV ones need a strong UV source.



Assuming one could actually obtain this stuff in small quantities the primer seems within the realm of driveway application. The hardcoat, probably not. To do that right would likely require some sort of dedicated chamber for application.



That's just GE products though. If somebody has a lot of time on their hands (it's 109 pages), please troll through:



http://esales.lgmma.com:2104/html/pdf/k/AMECA.pdf



which is a list of everything that is approved for headlight repair, and see if there is anything in there that is easier to apply.
 
what about using the 3m clear protection film after a headlight restore. im not sure of its UV resistant properties, but that would create a lifelong seal... no?
 
I've seen people do it, but I don't think you could wrap all lights completely. I wonder if the manufacturer approves of their product being applied to lighting due to safety issues. Not to mention the temps some lights can get.
 
i have a 3m tint on my headlights... its been on for 2 yrs. no problems. but i dont see have the clear would have any safety side effects at all. its not obstructing the light... and if anything i think its more guaranteed to give an even finish where as the urethane mix could go on thicker and thinner in some sports and cause some odd light refraction.
 
From the 3M site: FAQs



Q. Can Scotchgard™ Paint Protection Film be used on headlights, foglights or windshields?

A. No, the Department of Transportation does not allow any film of any kind to be put on headlights, foglights or windshields.
 
In my opinion you just high speed the crap out of them....You DONT need to seal them with anything. I turn them to clear glass if they arent too far gone. All plastic will re-age with time. You wont be able to do anything about that. If the lens is yellow it needs replacing. Just the facts.
 
Believe it or not, I used this 3M Headlight Restoration kit in combination with wet sanding, to restore the headlights on my wife's 2002 Grand-Am, and it worked great.
  1. I wet-sanded the headlights by hand over the course of two days, starting with 800, 1000, 1500, 2000, and 2500 grit sandpapers in that order.
  2. I didn't use any of the sandpaper discs that came with the kit, except for the 3000 grit foam padded disc that it came with for the last sanding step.
  3. After using the 3000 padded sand paper disc with the a cordless drill, I then used the 3in foam pad that comes with the kit, with 3M rubbing compound to get rid of any sanding marks left over, and make the headlights as clear as possible.
  4. I washed the 3in pad and let it dry over night, before repeating usage of the 3in pad, but this time I used Attwood Fiberglass Restorer
  5. Once again, washed and dried the pad, and repeated again, using Attwood Marine Cleaner Wax.
  6. Then as the last step, I gave it a couple of coats of Collinite #885, followed by a couple of coats of Collinite #925.
  7. Every now and then I QD her headlights, and give them another coat of Collinite #925 to help maintain them.
This was all done this past June, and her headlights are still looking pretty good. They were literally yellow around the time I decided to give it a try to restore them. When I was done they were clear as new. Was a royal pain in the ***, and was very time consuming, but the way I saw it, it was worth doing it right the first time, and not having to worry about it again for a while. So far, so good.



:xyxthumbs





Here's a link to the kit I used, and also a video on the same page demonstrating it:



Shop 3M: 3M Headlight Lens Restoration System, 39008
 
David Fermani said:
Good info - that's what I thought.
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Seriously, that tidbit proves absolutely nothing outside of being a legal disclaimer.



The USDOT doesn't officially allow the vast majority of mods and upgrades that auto enthusiasts perform upon their vehicles. Doesn't mean such things don't yield a net gain in whatever area they pertain to. Just means they don't meet an inane spec that could very well be several decades old. And I'm NOT referring to LED washer nozzles, blue turn signal bulbs, et al.



In a lot of areas of design, the USDOT is an organization with archaic regs that inadvertently keep vehicle development behind the European-standard curve. Ironically, one such area is that of lighting design.



Our cars would be a hair cheaper and faster, as well as significantly easier on the eyes, if the USDOT basically disappeared, in favor of adopting the official euro regulations.



By 3M acknowledging that their film is disallowed for headlight and windshield use, they are basically just bowing down to a federal decision that was made before the modern era of PPF films. The current stuff is used all the time on headlights and windshields applications with no long-term ill-effects.
 
It's about liability. If you get into an accident and the light that had film on it got destroyed and required replacement, your insurance company would be wrong for authorizing or paying to have the film put back on because of this "legal disclaimer". Same does for manufacturer guidelines/recommendations.
 
Klasse SG seems to dry very fast on plastic for some reason and doesn't streak. I learned this from testing it on my mirrors and later started doing it on the headlights after every wash. It'll be dry enough to remove in just an hour or so, depending on humidity. You can even do the wipe on wipe off method of SG application, that's super easy on plastic! Almost fool proof. Pretty soon you'll have multiple coats on the lenses.
 
well couldnt you argue the same thing about them saying 'who put all this urethane on your headlights... that probably caused your accident' ?



the same thing goes for the tinted/colored license plate covers. says right on them check you local laws before using. no one does... they just put them on. i did to. i was unlucky enough to get nailed for it though while i cop was telling me all the other things wrong with my car. but, 99.9% of people get away with it.
 
sal329 said:
Im not sure what the "best" is but I use 3 coats of FK 1000p
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I'm lazy today, and didn't read the whole thread, so if this has already been covered, I apologize...



Anyway, just wanted to say that I'm with sal329. 1000P is great on headlights. I try to stay with sealants on headlights, as they are capable of withstanding the heat from the headlight better than waxes, IME/O.
 
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