An anti-reflective (AR) eyeglass coating can improve vision dramatically, especially in snow, but when the coating is scratched, it impairs vision. The coating isn't supposed to be removable, but you can get it off. The process depends on whether the glasses have plastic or glass lenses. You use a glass etching compound on plastic lenses, but when it comes to glass lenses, you mechanically scrape off the coating after softening it with isopropyl alcohol.
AR Coatings Adhere by an Electrostatic Bond
An AR coating is a microscopically thin layer of metal oxides that is applied to the lenses in a vacuum. The coating materials are carried by a stream of electrons, creating an electrostatic bond that is much stronger than a mechanical one, such as would exist if the coating were applied with adhesive. Any effort to remove coating applied by this process by scraping or abrasion is likely to damage the lens.
Electrostatic coatings are used in the auto industry to create long-lasting finishes, and when a refinisher has to remove one, the options include abrasion, caustic strippers and electrostatic conversion. Although the last option sounds promising, there's no evidence that anyone has ever tried it for glasses or that it would work. That leaves the first two options, although you obviously need different materials to remove coatings from glasses than you do from metal.
Removing an AR Coating From Plastic Lenses
Because polycarbonate lenses are not glass, you can use a glass etching compound to remove the AR coating without damaging the lenses. The most popular etching compound used for this purpose contains sulfuric acid, but if you find a product that contains hydrofluoric acid, it also works, according to a lens manufacturer. Just wipe the product on the lens using a nonabrasive cloth, give it time to work and then wipe it off and clean the lenses with soap and water. Whenever you use a commercial product, read the instructions before you actually apply it.
Removing an AR Coating From Glass Lenses
When it comes to glass lenses, the options for removing a scratched AR coating narrow to one: mechanical abrasion or scraping. You need a plastic scraper because a metal one is sure to scratch the glass. A plastic stove scraper makes an ideal tool.
Before you actually get down to scraping, it's important to soften the coating. One way to do this is to soak the glasses for at least 10 minutes in a 90 percent solution of alcohol diluted with a small amount of water. Although 10 minutes is the minimum soaking time, the job of scraping may be easier if you increase it to 30 minutes or an hour. Once the coating is soft, it shouldn't take any more than 10 minutes to scrape it off with the plastic scraper. Be sure to clean the lenses with soap and water when you're done.
About the Author
Chris Deziel holds a Bachelor's degree in physics and a Master's degree in Humanities, He has taught science, math and English at the university level, both in his native Canada and in Japan. He began writing online in 2010, offering information in scientific, cultural and practical topics. His writing covers science, math and home improvement and design, as well as religion and the oriental healing arts.