Does Glass Block UV Light? Let’s Find Out!

glass block uv light

The answer is Yes and No – stay with me here and I will explain. First of all, there’s a popular saying “you can’t get a sunburn through a glass”, you’ve heard the saying or might have even said it yourself right? Well, the truth is you might not get a sunburn, but it’s a far cry from reality to assume you’re safe from the effects of UV rays once you’re behind a glass or window.

Glass does block UV light, but not entirely. A regular window blocks UVB light very well, but UVA manages to go through it. And that would mean your skin might get affected in the long run.


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We ran together three sequences of the Sun taken in three different extreme ultraviolet wavelengths by our Solar Dynamic Observatory (SDO) to better illustrate how features that appear in one sequence are difficult, if not impossible, to see in the others (Mar. 20-21, 2018). In the red sequence, we can see very small jets of solar material burst from the Sun’s surface and some small prominences, bright features extending outward, at the edge, which are not easily discerned in the other two sequences. In the second clip, we can readily observe a coronal hole, the large and dark region where the Sun's magnetic field is open to interplanetary space, though it is difficult to distinguish in the others. In the third clip, we can see strands of plasma waving above the surface, especially above the one small, but bright, active region near the right edge. These are just three of the 10 extreme ultraviolet wavelengths in which SDO images the Sun every 12 seconds every day. That's a lot of data and a lot of science! Credit: NASA/Solar Dynamics Observatory #nasa #space #sun #solar #sdo #light #earth #solarsystem #science #video #ultraviolet #uv #uvlight #picoftheday

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Before continuing here’s what you need to know about these UV light:

What does UV mean?

UV is the acronym of Ultra-Violet light, this is a term used to describe a relatively wide spectrum of wavelength ranging from 400nm to 100nm. It is basically the invisible part of the electromagnetic spectrum; falling between the violet visible light and x-rays.

There’re different types of UV rays, but our interest is in the UVA and UVB types. These two are the ones posing a major health risk for you if ignored.


What has UV got to do with your health?

Remember those irritating reddish spots on your skin when you stay out under the sun for long without wearing a sunscreen? – Sunburn? That’s right. You didn’t just develop them – this UV light caused them and if left untreated could lead to skin cancer.

That’s not all – do you know, even without stepping out to the sun that is consistently staying under a shade, maybe behind a glass – your skin can still get damaged by this same UV? Albeit by a different type.

The thing is: UVB causes sunburn and possibly leads to skincare while UVA causes skin wrinkles and aging.


Does glass play any role in protecting against UV?

Yes, staying behind a glass or window surely helps to provide a level of protection against UV light – there’s a reason for this. Remember UVA and UVB? Window glasses generally absorb UVBs effectively preventing sunburns and skin cancer while UVAs easily penetrate through the windows and affect the skin.

Though the intensity and amount of UVA which passes through these windows can be minimized using specially treated glasses. Hence for an ordinary clear glass, about 75 percent of UVA passes through while for Tinted and reflective glasses, about 25 – 50 percent of the rays go through still.

However, a specially designed glass such as laminated and UV-blocking coated glass can provide sufficient protection against the effects of both UVA and UVB. By effectively blocking out 95 – 99 percent of all UV light.

Hence, even while sitting behind a window, don’t take it for granted that the glass is protecting you from UV – in this case, it’s just half-truth.

And yes, you can use a makeup mirror without worrying whether you’ll get a sunburn or not. Usually, mirrors are coated with a layer of aluminum on the back of the glass, which absorbs the UV rays, therefore, the light reflected should be inoffensive to your eyes or skin. Check out this post in which we’re covering the best-lighted makeup mirrors.


How to protect yourself against UV light in your car

More and more people are spending a greater portion of their time in cars – this is a feature of modern life and the trend is not slowing down anytime soon.

The result of this is the continual exposure of one side of the face to the UV light – leading to sun damage of one side of the face. (This is why you see some individuals with one side of their faces having more wrinkles than the other side, leathering, sagging, and even skin cancer on one side of their face)

This effect is clearly illustrated with the case of this man as posted on Huffington Post, who had a gradual, asymptomatic wrinkling of the skin on the left side of his face, after exposing this side of his face to the sun for over 28 years as a delivery truck driver.

So how do you protect yourself from UV while in a car?

The thing with car windows is: the windshield is usually built with laminated glass that blocks out most of the UV light but the rear and side windows are made from non-laminated glass. Leaving those places open for penetration by UVA. So get your auto mechanic to add tinting to your glass windows – this helps to reduce the UVA penetration to about 15 – 30 percent.

However, make sure the tinted glass compliances with the minimum visible light transmittance – which is about 70 percent in the United States.

Other protective measures to ensure you stay sun-safe in your car include wearing protective clothing such as long-sleeved shirts, UV-blocking sunglasses, hats with brims and long pants. All these measures, when followed, will ensure you’re safe from the adverse effects of the UV lights.


In Conclusion

We believe you’ve learned it is not enough to stay behind a glass window whether in your car or home and think you’re safe from the effects of UVs – especially UVA: which penetrates through glasses and causes skin aging. Even when in your home or inside a car, precautionary measures should be taken to keep you sun-safe and this includes wearing protective wears and using blinds for your home glass windows and tinting your car windows.

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Passionate about everything that shines, settled down on UV(ultraviolet) lights. I'm motivated and with a mission to help people live a better life!

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  1. So it’s safe to run a UVB light inside of a glass aquarium as long as the top is sealed, too? I don’t want to be giving my kids skin cancer inside of our own house.

    • Hey Christy,

      UVB is more dangerous than UVA light. My suggestion for you would be to use UVA lights and make sure that the aquarium uses laminated or UV-blocking coated glass since it’s absorbing more than 90% of the light. Place the UVA light strategically inside the aquarium and you all should be safe!



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