If you have in mind see the solar eclipse this August 12you may have already started searching approved glasses. Many shops they have jumped on the car and they are launching offers at a very reduced price. Although the truth is that, honestly, it is not necessary to lower the cost much, since the price of eclipse glasses is extremely cheap. And of course, for some people, it is very shocking, since they insist actively and passively that conventional sunglasses do not work for us, but how can my 100-euro Ray-Ban not be worth it and some cardboard glasses that cost me 3 are worth it?
With this, as with many things in life, we see that price is not everything. They are not lying to us when they tell us that sunglasses are worthless. They also don’t scam us by selling us eclipse glasses for only 3 euros. The inflated prices of brand name sunglasses can sometimes hurt us like a scam, although everyone is free to set the prices for their brand that they see fit. But let’s focus on the science of approved glasses. How can something so technically necessary be so cheap to produce?
There is not so much technical complexity. Eclipse glasses are designed to be used once in a very long time, if at all. Normally, the person who wears them just look at the sky and, at most, around it. You don’t have to drive, walk, or read anything. You just stop and look at the Sun. For this reason, all you need is a very basic frame, sometimes made of cardboard, and two filters, one for each eye.
Sunglasses, on the other hand, must be functional, which requires greater technical complexity. If they are graduated, It is necessary that they have an adequate curvature. This is not necessary in itself for non-prescription sunglasses, but it is often also done to give them a more enveloping effect, especially if they are aimed at sports. On the other hand, the glass of the sunglasses is carved, polished and treated to improve visibility and prevent scratches. For this reason, their manufacture is more expensive, while the price of eclipse glasses is very low.
Simple but essential filters. The really important thing about approved eclipse glasses is that they have good filters. These must comply with the regulations EN ISO 12312-2:2015which ensures that no more than 0.00032% of visible sunlight is allowed to pass through. Sunglasses, on the other hand, are designed to avoid indirect damage, but not to look directly at the Sun, so a transmittance of 3% is sufficient in the highest protection categories.
The filters used to achieve this great light blocking in eclipse glasses are manufactured with a black polymer or resin with carbon particles. The most used polymer is reflective Mylar.. Then, on top of the polymer, they have thin layers of aluminum, chrome or silver, which help optimize filtering. They are not difficult materials to obtain in the necessary quantities, so the final price is not exorbitant.
There is no exclusivity, another reason for the price of eclipse glasses. Even if cheap materials are used, the filter still costs money. The thing is that, unlike what usually happens with sunglasses, eclipse glasses are usually produced on very large scales. Exclusivity is not sought nor does anything happen because there are many identical glasses. That, in the end, reduces costs a lot.
Furthermore, with sunglasses we often pay for the brand and that is something that, logically, does not matter with glasses approved for viewing the eclipse.
Even given as gifts. Producing these glasses is so cheap that some brands, businesses and institutions are already giving them away to ensure that we all see the eclipse on August 12 safely. In Spain, this will be the first of three eclipses in three consecutive years; So, contrary to usual, you will need these glasses again very soon. Whatever you buy, don’t get rid of them. Of course, if you see that the filter is broken or scratched, the protective metal layers may be damaged and good filtering is no longer guaranteed. In that case, buy others. After all, they are justifiably very cheap.
Image | Magnific/NASA
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