# Is there a way to tell if sunglass lenses are "UV blocking" using common household materials? **URL:** \ **Category:** Factual Questions\ **Created:** [March 30, 2026, 9:41pm UTC](https://boards.straightdope.com/t/is-there-a-way-to-tell-if-sunglass-lenses-are-uv-blocking-using-common-household-materials/1028895 "2026-03-30T21:41:06Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Drum\_God](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drum_god/32/44_2.png) [@Drum\_God](https://boards.straightdope.com/u/Drum_God)\ **Post date:** [March 30, 2026, 9:41pm UTC](https://boards.straightdope.com/t/is-there-a-way-to-tell-if-sunglass-lenses-are-uv-blocking-using-common-household-materials/1028895/1 "2026-03-30T21:41:06Z")
I bought a pair of sunglasses while on vacation in Mexico. I am quite certain that the sunglasses are not made by the manufacturer indicated by the trademark on the glasses. (For one thing, the trademark was easily scraped off using my thumbnail.) So, I know that the glasses are counterfeit. Is there a way for me to determine if the lenses truly protect my eyes from unwanted UV light? ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [March 30, 2026, 10:17pm UTC](https://boards.straightdope.com/t/is-there-a-way-to-tell-if-sunglass-lenses-are-uv-blocking-using-common-household-materials/1028895/2 "2026-03-30T22:17:17Z")
You can get UV cards that change color when exposed to UV rays. I’d probably start with one of those, confirm it changes color in the sun, then see if it changes color if it’s covered with the sunglasses. ETA, I’m not vouching for this, it’s just the first one I saw. If you watch BigCliveDotCom on youtube, he uses these from time to time, but I couldn’t tell you what brand he uses/prefers. [https://www.amazon.com/QuantaDose-Light-Power-Visibility-Technology/dp/B08KZZ54BZ](https://www.amazon.com/QuantaDose-Light-Power-Visibility-Technology/dp/B08KZZ54BZ) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 30, 2026, 10:30pm UTC](https://boards.straightdope.com/t/is-there-a-way-to-tell-if-sunglass-lenses-are-uv-blocking-using-common-household-materials/1028895/3 "2026-03-30T22:30:41Z")
You also want to distinguish between different kinds of UV. UV-B, the higher frequency kind, is blocked by ordinary glass (and probably a lot of other materials). UV-A, which is more prevalent in sunlight, requires more special materials to block. ---
**Author:** ![ricepad](https://avatars.discourse-cdn.com/v4/letter/r/b38774/32.png) [@ricepad](https://boards.straightdope.com/u/ricepad)\ **Post date:** [March 30, 2026, 10:33pm UTC](https://boards.straightdope.com/t/is-there-a-way-to-tell-if-sunglass-lenses-are-uv-blocking-using-common-household-materials/1028895/4 "2026-03-30T22:33:03Z")
Blue Lizard brand sunscreen has either a label or a cap (I forget which) that changes color when exposed to UV light. I don’t know if it distinguishes between UVA and UVB or not, though. EDITED TO ASK: How much did these fake shades cost? It might be cheaper than some of the solutions recommended in this thread. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [March 30, 2026, 10:34pm UTC](https://boards.straightdope.com/t/is-there-a-way-to-tell-if-sunglass-lenses-are-uv-blocking-using-common-household-materials/1028895/5 "2026-03-30T22:34:06Z")
I would get a UV LED flashlight (they are really cheap these days), and use a “blued” t-shirt, or a piece of fluorescent paper, and see how much the lens attenuates the UV. I bought some amber UV-tinted goggles to use with a very high-power UV resin curing light, and I wanted to see how much UV they actually blocked, and this is what I did. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [March 30, 2026, 10:36pm UTC](https://boards.straightdope.com/t/is-there-a-way-to-tell-if-sunglass-lenses-are-uv-blocking-using-common-household-materials/1028895/6 "2026-03-30T22:36:54Z")
The thing is, almost all sunglasses will block harmful UV rays. The hard part is making materials that _transmit_ harmful UV rays. I know – I’ve had tp do it. Virtually all plastics and glasses block light below 300 nm, and most block it below 400 nm. Here’s the transmission of acrylic, for instance. It stops at 400 nm. > **[Optical Transmission Properties of Acrylic](https://www.sanatron.com/blog/optical-transmission-properties-of-acrylic.php?srsltid=AfmBOoqFGhWxQUCBQnpWeploJsYHCHBt8Prdm1q8iMTO8Qtrv7y3gR6L)** “UV acrylic” transmits below 400 nm, but you have to pay extra for it. Here’s a bunch of different plastics. Note that, except for the UV acrylic, they stop at 400 nm: > **[Transmission Curves for Polymer Optics](https://gandh.com/news-and-resources/transmission-curves-for-polymer-optics)** > > Transmission is a parameter of optical performance. For polymer optics, transmission is limited by Fresnel reflection, scatter and material absorption. Here’s PMMA (plexiglas) [https://www.semanticscholar.org/paper/Transmission-curves-of-plexiglass-(PMMA)-and-grease-Joram/3fb7da82d518652028dae523ac50f448870bc443/figure/0](https://www.semanticscholar.org/paper/Transmission-curves-of-plexiglass-(PMMA)-and-grease-Joram/3fb7da82d518652028dae523ac50f448870bc443/figure/0) Polycarbonate (the stuff my eyeglasses are made of) stops at 390 nm > **[OptiCampus.com - Spectral Transmittance Charts](https://opticampus.opti.vision/tools/transmittance.php)** > > OptiCampus Online Optical Continuing Education ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [March 30, 2026, 10:38pm UTC](https://boards.straightdope.com/t/is-there-a-way-to-tell-if-sunglass-lenses-are-uv-blocking-using-common-household-materials/1028895/7 "2026-03-30T22:38:54Z")
Virtually all sunglasses block beloe 380 nm > **[Transmission Characteristics of Sunglasses and Tinted Windows](https://www.gmp.ch/spectroscopy-applications/transmission-characteristics-of-sunglasses-and-tinted-windows)** > > To evaluate a range of eyewear options, we tested six samples ranging from discount store sunglasses to luxury brand eyewear... ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 30, 2026, 10:53pm UTC](https://boards.straightdope.com/t/is-there-a-way-to-tell-if-sunglass-lenses-are-uv-blocking-using-common-household-materials/1028895/8 "2026-03-30T22:53:19Z")
> [@CalMeacham](#): > > Here’s the transmission of acrylic, for instance. It stops at 400 nm. > [@CalMeacham](#): > > Here’s PMMA (plexiglas) I had thought that plexiglass was just the most common brand name for acrylic. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [March 30, 2026, 11:05pm UTC](https://boards.straightdope.com/t/is-there-a-way-to-tell-if-sunglass-lenses-are-uv-blocking-using-common-household-materials/1028895/9 "2026-03-30T23:05:25Z")
So said another way, purported special UV blocking features of sunglasses are pure marketing ouffery devoid of substance. In other news, Dasani sells the wettest water. ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [March 31, 2026, 3:06pm UTC](https://boards.straightdope.com/t/is-there-a-way-to-tell-if-sunglass-lenses-are-uv-blocking-using-common-household-materials/1028895/10 "2026-03-31T15:06:04Z")
> [@Joey\_P](#): > > You can get UV cards that change color when exposed to UV rays. I’ve got one, that’s the way to go. It has sections that react to different freq/wavelengths to distinguish, say, UV-A vs C. It was a couple bucks on Amazon at the time, more now! I confess I first misunderstood how they worked and thought it laggily charged up like glow in the dark phosphors. I was leaving it in direct sunbeams for a minute and rushing it inside to see the reaction: none found. Then, I tried it in a UV-C chamber and found the same unreacted card when I took it out for inspection. [https://www.amazon.com/QUANTADOSE®-Multi-Wavelength-Bi-Luminescent-Reusable-Professional/dp/B0BK1772JY/](https://www.amazon.com/QUANTADOSE%C2%AE-Multi-Wavelength-Bi-Luminescent-Reusable-Professional/dp/B0BK1772JY/)