Sun's rays dim lenses over time

By Doug McAllister

Q. I enjoy you informative column and hope you can offer some advice about plastic headlight lenses. The headlight lenses on my 2001 Honda Odyssey have clouded over the years, and I have had them professionally restored/polished to make them clear. I have also done the restoration polishing twice myself. While I have been successful in restoring the lenses to almost new condition each time, my questions are:

1) What causes the lenses to cloud over time? Is it UV exposure, chemical exposure or something else?

2) Is there something I can do to prevent, reduce or mitigate the cause of the plastic getting cloudy?

3) Since the headlight restoration product I use (Rain-X Headlight Restorer) acts like a mild abrasive, is there a limit to how many times I can use this product until I wear out or damage the headlight lens to the point where polishing will not work anymore?

I have two newer cars in the family that have not shown any headlight lens clouding yet, and I would like to do what I can to avoid having to keep on polishing the lenses. What do you suggest?

A. Great questions. It is primarily the UV exposure that degrades the plastic lenses. When they are new there is a coating on them that inhibits the exposure but it wears off over time.

The natural impact from sand and road grime does not help, either. When we do the headlight restoration, we use three or four grades of abrasive with the final sanding being extremely fine (3000 grit). We do the sanding with orbital pneumatic tools that run at different speeds. We then finish if off with a polish that has a UV inhibitor.

We have had good luck with this process and it seems to last so I am not sure why you have had to do them so often. I am sure the farther you sand into the plastic the less effective it will be.

The best thing you can do for headlight lenses that are still in good shape is to keep them clean and waxed. This will help protect them as best you can. Taking the time or spending the money to clean up those cloudy lenses is well worth it; not only will you have better vision at night but it makes the whole car look much better.

I hope this helps.

• Douglas Automotive is at 417 W. Main St., Barrington; 123 Virginia Road, Crystal Lake; and 416 Northwest Hwy., Fox River Grove. For information, visit douglasautomotive.com. Send questions to underthehood@dailyherald.com.