Speaker 1: Welcome to Brainstuff from half stuff works dot com, where
Speaker 1: smart happens him Marshall Brain with today's question, is there
Speaker 1: a way to make my sunglasses scratch resistant? Reflective sunglasses
Speaker 1: often have a mirrored look. The lenses in these sunglasses
Speaker 1: have a reflective coating applied in a very thin, sparse layer,
Speaker 1: so thin that it's called a half silvered surface. The
Speaker 1: name half silvered comes from the fact that at the
Speaker 1: molecular level there are reflective molecules speckled over the glass
Speaker 1: in an even film, but only about half of the
Speaker 1: glass is actually covered by these speckles. The half silvered
Speaker 1: surface will reflect about half the light that strikes it,
Speaker 1: letting the other half go straight through. Often the mirror
Speaker 1: coating is applied as a gradient gradually changes shades from
Speaker 1: top to bottom. This provides additional protection from light coming
Speaker 1: in from above, while allowing more light to come in
Speaker 1: from below or straight ahead. This means that if you're driving,
Speaker 1: the sun's rays are blocked, but you can still see
Speaker 1: the dashboard. Sometimes the coating is bigradient. It's shaded at
Speaker 1: the top and the bottom, but it's clear in the
Speaker 1: middle of a lens. The big problem with these half
Speaker 1: silvered sunglasses is that the coating is really easy to scratch,
Speaker 1: while the glass itself is naturally scratch resistant. The coatings
Speaker 1: apply to the glass as well as the most plastic
Speaker 1: lenses are not scratch resistant. To compensate for this, manufacturers
Speaker 1: have developed a variety of ways to apply optically clear,
Speaker 1: very hard films to lenses. These films are made of
Speaker 1: materials such as diamond, light carbon, and polycrystalline diamond. Through
Speaker 1: a process of ionization, a thin, but extremely strong film
Speaker 1: is created on the surface of the lens. This scratch
Speaker 1: resistant coading works well in most cases. For example, you
Speaker 1: can buy plastic lenses that are incredibly hard to scratch
Speaker 1: because of these codings. But manufacturers have not been able
Speaker 1: to successfully apply a scratch resistant layer on top of
Speaker 1: the reflective coating used in mirrored sunglasses. Therefore, the scratch
Speaker 1: resistant coding is applied first to protect the lens, and
Speaker 1: then the reflective coding is applied over it. What this
Speaker 1: means is that you have to take special care of
Speaker 1: your reflective sunglasses or they get scratched really easily. For
Speaker 1: more on this and thousands of other topics, Does that
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