Experiment on headlight restoring methods

[The Whispering Gallery]

Does any data exist that compares various methods of headlamp lens restoration to that of brand new, OEM headlights, quantified by the percent of light transmitted through the lenses? If not, I'm thinking about doing such an experiment.

I would propose to test several samples cut from an old headlamp lens (ideally one that is flat), restoring them by completely sanding off the damaged factory UV-protection layer, and then applying some of the commonly used restoration coatings, such as spar urethane, automotive clear coat, etc, according to the "established procedures." I would also test an unrestored sample of the old lens and ideally a sample of a brand new lens, characterizing all samples with the UV-vis spectrometer to which I have access.

Previously, I restored my headlights with some automotive clear coat with pretty good results (to my eyes), but I'd really like to quantify how close (or far) a restoration comes to approaching the quality of a new headlamp lens. I realize that there are some other reasons besides how well the lens transmits light, such as degradation of the materials on the headlamp internals, that a new headlight would have better performance than an old one.

I'd be willing to purchase the junkyard headlamp and coating materials, but does anyone know where I can get some small samples of a new lens for cheap?

 

[Lynx_Arc]

One way to get samples of a new lens is to contact a fire station. Around here when there is an accident they clean up some of the debris and I'm sure at times there are broken lenses in that debris.

 

[fastgun]

Please do post if you undertake this. Headlight restoration will continue to be a growing trend for years to come.
On other sites there is an on going observation of how well an Optilens headlight weathers compared to a helmsman spar coated one.
The fella is in Hawaii and has the headlight on the roof of his house 24/7.. His criteria is just how they look compared to a new one.
If you would test for light transmission that would be interesting.

 

[The Whispering Gallery]

One way to get samples of a new lens is to contact a fire station. Around here when there is an accident they clean up some of the debris and I'm sure at times there are broken lenses in that debris.

Interesting, had not thought of that. I'll see if my local fire station can help me out.

Please do post if you undertake this. Headlight restoration will continue to be a growing trend for years to come.
On other sites there is an on going observation of how well an Optilens headlight weathers compared to a helmsman spar coated one.
The fella is in Hawaii and has the headlight on the roof of his house 24/7.. His criteria is just how they look compared to a new one.
If you would test for light transmission that would be interesting.

I will definitely post if I get results. I did purchase some Lightrite as well for my own headlamps so I can include that in the test. Perhaps I can find someone to send me a small sample of Optilens as well since it is a bit expensive to purchase just for this test. I was also thinking about leaving the samples outside and testing them periodically for long-term comparison.

It would be really nice to have old and new headlamps from the same model.

 

[Alaric Darconville]

Does any data exist that compares various methods of headlamp lens restoration to that of brand new, OEM headlights, quantified by the percent of light transmitted through the lenses? If not, I'm thinking about doing such an experiment.

It's not just the percent of light, it's also things like if the lens is malformed by polishing such that it takes on multiple changes in diopter across the surface of the lens, such that a ray of light passing through the lens, instead of proceeding straight out the lens, is actually refracted and changes direction. The amount of light passing through the lens is the same-- but it's now not in the right beam pattern. *Probably* not a bunch to worry about, but still-- a polished lens is never quite the same as a new one, especially when polishing required sanding off the rest of the UV protective coating.

 

[The Whispering Gallery]

It's not just the percent of light, it's also things like if the lens is malformed by polishing such that it takes on multiple changes in diopter across the surface of the lens, such that a ray of light passing through the lens, instead of proceeding straight out the lens, is actually refracted and changes direction. The amount of light passing through the lens is the same-- but it's now not in the right beam pattern. *Probably* not a bunch to worry about, but still-- a polished lens is never quite the same as a new one, especially when polishing required sanding off the rest of the UV protective coating.

Yeah I was just thinking about that issue as well, which of course could only be characterized by comparing the beam pattern/photometric test of the full refinished headlamp and new headlamp. Not something that could be quantified with a transmission test of a small sample. I'll still do the test though if I can get a sample of a new lens since I'm curious to know what is the absolute best you can hope for when refinishing.

 

[Alaric Darconville]

Yeah I was just thinking about that issue as well, which of course could only be characterized by comparing the beam pattern/photometric test of the full refinished headlamp and new headlamp. Not something that could be quantified with a transmission test of a small sample.

And probably also really only affects the more careless "restores".

 

[fastgun]

Alaric's last post speaks truth.
It is amazingly easy to melt beyond repair a headlight lens with an orbital sander/polisher even with a finishing pad.
The better choice for most users may be the random orbital polishers as these will stop rotating long before they will do harm.
Even hand sanding can bring amazing results both good and bad depending on the person not the tool. The draw back has been a suitable final coat that will prevent the need to redo the polish. However, there are products on the market that are lasting for several years. For the cost of one of the least expensive, crummy, aftermarket, junk headlights a person can restore both of their factory headlights and obtain clarity for years.

With reasonable care and effort to learn the correct methods, I suspect that the seasonal summer to winter temperature changes cause more variance to a headlight lens than a decent restoration. But reasonable care and decent restoration are not standardized terms.