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If you’ve ever felt the pain of putting on sunglasses after letting them sit in a hot car, you’ve probably become a little more careful about where you leave your shades. But besides burning yourself, did you know that leaving your sunglasses in hot places can lead to other problems? In fact, letting your glasses get too hot can seriously affect your lenses and permanently damage them.
To understand how heat can harm your sunglasses, we first need to take a look at how your sunglass lenses are made.
Polarized lenses contain a special film that allows light to pass through the lens while simultaneously blocking glare. When polarized lenses are made, the film in the lens is cured using heat. If the lens and film are heated up again, it can cause issues. The polarized lenses will also have a scratch coating to protect the lens against scratching. The lens tends to stretch when it is heated up, but the film and scratch coating doesn’t expand at the same rate. This can cause the film or scratch coating to crack.
Sunglasses may have an anti-reflective coating with even less flexibility. The sunglasses with an anti-reflective coating are more susceptible to heat; they contain thin layers of glass that will not stretch. This ultimately leads to cracking and breaking.
No matter what type of sunglasses you have, leaving them in sun is never a good idea and definitely not recommended. Making sure you don’t leave your sunglasses in your car on a hot day is an easy way to preserve your lenses. In fact, even on days when the temperature is only 60 degrees, the temperature inside your car can easily reach 100 degrees. And on hot, summer days that reach temperatures of 100 degrees, your car can heat up to 140 degrees in just 15 minutes! But cars aren’t the only place that can overheat your sunglasses. Leaving sunglasses next to the pool on a hot day can lead to high lens temperatures. Another common problem is taking glasses off during a trip to the steam room and leaving them near the heat source.
As the temperatures start to warm up this summer, remember to shield your shades from the heat, so they can continue to protect your eyes all summer long.