The headlight "restoration" I did last year when I first bought the car (ie. the Meguiars headlight polish kit) was only ever going to be a stop gap at best as there were several problems with the lens. As eventually happens to every headlight that uses a polycarbonate lens, the factory UV sealant was visibly breaking down causing some cloudiness/yellowing plus 11 years of road use had taken their toll leaving some pitting and sandblasting. My lights certainly weren't the worst I've ever seen, but they weren't in the greatest shape and the wear was causing some light diffraction and scatter. Thus, inspired by this thread on Dubberz, I decided to do a full and proper restoration of the lens (which also gave me a convenient excuse to finally replace the old tired outer lens gaskets with the replacements I bought last fall).

The main components of any standard restoration are sanding off the old sealant and top plastic layer to expose a fresh surface then polish it back to clarity. Many people do this by hand, starting with dry sanding at 150 - 300 grit for heavily damaged surfaces and moving on to wet sanding down to 3000 grit before polishing with a plastic rubbing compound. Personally I'm lazy and the thought of hand sanding sounded pretty labour intensive so I choose to go the route of the 3M Headlight Restoration System which provides 3 grit levels (500 dry, 800 dry and 3000 wet) plus the polishing compound and is designed to work on a household drill.

This was the starting point. Not too bad but any gains from the polishing from last summer had long since disappeared. As a result the lens was a bit clouded and quite pitted.



The dry sanding with 500 grit took the longest to complete as the purpose of this step is to remove all the remaining factory sealant as well as the pitting in the lens itself. The goal here is to achieve a smooth surface with a uniform appearance of frosted glass.



The 800 grit stage was MUCH faster and easier than the 500, the purpose is just to reduce 500 grit the scratches from the previous step to finer scratches. Again the goal is a smooth uniform surface that looks like slightly less frosted glass.



The P3000 grit foam disc is a wet sanding step meant to dramatically reduce the 800 grit scratches from the last step. You need to constantly apply water to the lens surface, when finished the lens should be quite clear, only a slightly noticeable cloudiness from fine scratches should remain.



Finally we buff and polish the lens using the foam polishing pad and polishing compound. After this stage the lens should be restored to full clarity and should look factory new. As you can see, there is a SIGNIFICANT difference between the restored and non-restored headlights!





Unfortunately all that work will quickly be undone if the fresh surface is not protected, and while you can use wax to help, the best solution is to apply a UV sealant like the lenses had from the factory. Most sealants are not available in Canada due to environmental regulations, do I chose to follow the recipe in the above thread to mix mine own from a 50:50 ratio of Miniwax Helmspar Clear Gloss urethane-based varnish and mineral spirits. You don't need to mix much sealant, 3 tbls of helmspar and 3 tbls of mineral spirits was way more than enough to do these lights.

The application was relatively simple, a very thin coat of sealant applied over the entire lens surface following a through cleaning with raw mineral spirits. I used a blue shop towel folded down to a 1.5" square as an applicator pad. Basically you want to soak the end of the applicator in the sealant almost to the point of dripping then wipe it across the lens in even overlapping strokes. I did take several attempts to perfect the technique, but the sealant is very forgiving and is easily removed with mineral spirits if you make a mistake and need to start over. Due to the long wide shape of the C5 headlights I found the best method was to run in short wipes from the top to the bottom of the lens instead of trying to go length wise across the lens. I did also apply sealant all around the outside edge of the lens before installing the new gaskets.

This is the completely restored headlight. The sealant is self-leveling so it fills in most of the extremely fine scratches that the polishing stage doesn't completely remove and adds a deep glossy finish to the lens in the same manner that clear coat does with paint. I used my bathroom (with the window open and clear fan on) as a paint booth, the sealant dried to the touch in about 2 hours with the heater cranked to max. I re-installed the headlights after about 4 or 5 hours of curing time.



The finished product, I am very pleased with how well this process turned out. The cutoff from my HID's is much sharper and less diffused, plus the light output is whiter and nominally stronger as the yellowing had been tinting the lens and the diffraction eliminated.