Welcome to Brainstuff from half stuff works dot com, where smart happens him Marshall Brain with today's question, is there a way to make my sunglasses scratch resistant? Reflective sunglasses often have a mirrored look. The lenses in these sunglasses have a reflective coating applied in a very thin, sparse layer,
so thin that it's called a half silvered surface. The name half silvered comes from the fact that at the molecular level there are reflective molecules speckled over the glass in an even film, but only about half of the glass is actually covered by these speckles. The half silvered surface will reflect about half the light that strikes it, letting the other half go straight through. Often the mirror coating is applied as a gradient gradually changes shades from
top to bottom. This provides additional protection from light coming in from above, while allowing more light to come in from below or straight ahead. This means that if you're driving, the sun's rays are blocked, but you can still see the dashboard. Sometimes the coating is bigradient. It's shaded at the top and the bottom, but it's clear in the middle of a lens. The big problem with these half silvered sunglasses is that the coating is really easy to scratch,
while the glass itself is naturally scratch resistant. The coatings apply to the glass as well as the most plastic lenses are not scratch resistant. To compensate for this, manufacturers have developed a variety of ways to apply optically clear, very hard films to lenses. These films are made of materials such as diamond, light carbon, and polycrystalline diamond. Through a process of ionization, a thin, but extremely strong film is created on the surface of the lens. This scratch
resistant coading works well in most cases. For example, you can buy plastic lenses that are incredibly hard to scratch because of these codings. But manufacturers have not been able to successfully apply a scratch resistant layer on top of the reflective coating used in mirrored sunglasses. Therefore, the scratch resistant coding is applied first to protect the lens, and then the reflective coding is applied over it. What this means is that you have to take special care of
your reflective sunglasses or they get scratched really easily. For more on this and thousands of other topics, Does that house stuff works dot Com and don't forget to check out the Brainstuff blog on the house stuff works dot com home page. You can also follow brain Stuff on Facebook or Twitter at brain stuff HSW. The house Stuff Works I Find app has arrived down at it today on iTunes