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Tags blindness , glasses , light , sunglasses , sunlight , ultraviolet

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Old 6th June 2010, 12:41 PM   #1
Zelenius
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How to test sunglasses UV protection at home?

I'm skeptical of the claims made by many sunglass companies that claim their sunglasses provide 99% or 100% UV protection. Or they will say their glasses "block all UV light". There is almost never any independent verification of these claims. Some studies have shown many companies lie about their glasses UV protection - http://news.yahoo.com/s/livescience/...msstudyreveals

I also realize that darker lenses don't necessarily block more UV light than very lightly tinted glasses.

I realize optometrists and many eyeglass stores will have UV meters to test glasses to see how much UV light they let through, but I am interested in testing glasses myself. Is there a way to safely do this at home? I may borrow a UV flashlight from a friend just to test my sunglasses. I have very sensitive eyes, and some older relatives of mine have serious eye problems. So I want to do everything I can this summer to protect my eyes. Any suggestions?
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Old 6th June 2010, 01:06 PM   #2
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Your article is a dead link.
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Old 6th June 2010, 01:07 PM   #3
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You can buy UV meters on ebay for less than twenty dollars.
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Old 6th June 2010, 02:04 PM   #4
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I wonder if Radio Shack sells a UV "photovoltaic cell"? Probably cost $1. That and a voltmeter, and you would have UV meter... Calibrate it in and out of a window.

And Yes, you are right, it's usually the lens material that has the inherent spectrum limitation, NOT the tint. Clear glass blocks UV very well, the amber in beer bottles blocks visible BLUE light, preventing skunkiness. Link: http://realbeer.com/spencer/bottle.html

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Last edited by casebro; 6th June 2010 at 02:10 PM.
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Old 6th June 2010, 02:54 PM   #5
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Originally Posted by Harpyja View Post
Your article is a dead link.
I know how it happened too:

First he posted this on Social Issues & Current Events, where the displayed text for his link was automatically shortened with dots inserted within the text, which is something that vBulletin software does when URLs exceed a certain size.

Then he realized that he picked the wrong forum and made the mistake of copying and pasting his displayed first post onto a new thread in this forum instead of clicking the edit button and copying his actual entered text instead.

Unfortunately we can't recover his original link from the first post because he edited that to say "... please delete thread....".
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Old 6th June 2010, 04:55 PM   #6
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Originally Posted by Zelenius View Post
I realize optometrists and many eyeglass stores will have UV meters to test glasses to see how much UV light they let through, but I am interested in testing glasses myself. Is there a way to safely do this at home? I may borrow a UV flashlight from a friend just to test my sunglasses. I have very sensitive eyes, and some older relatives of mine have serious eye problems. So I want to do everything I can this summer to protect my eyes. Any suggestions?
Borrow the UV flashlight, turn the lights out at home, and shine the UV light on everything you have until you find something fluorescent (that is, something which glows in the dark when you shine UV light on it -- I think they tend to call those kind of fluorescent colours "fluro" here in Australia, "Day-Glo" in the UK and "Neon" in the US). Highlighters are often fluorescent.

Then you shine the UV flashlight through the lens of the glasses, and see if the object still glows in the dark.

Not a precise way of checking to see if the sunglasses filter UV light -- it won't tell you if it's filtering all of it or just some of it, but at least you can test if they're actually doing something or not, and it won't cost you a cent to try.

Originally Posted by casebro View Post
And Yes, you are right, it's usually the lens material that has the inherent spectrum limitation, NOT the tint. Clear glass blocks UV very well, the amber in beer bottles blocks visible BLUE light, preventing skunkiness.
Actually, clear glass blocks low-IR, not UV. I have a "blacklight" (UV) globe at home, and the UV very definitely passes through clear glass.
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Old 6th June 2010, 06:05 PM   #7
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Blacklights are usually UV-A, the least harmful range. More highly desired protection is UV-B and -C.

From <http://almashriq.hiof.no/lebanon/600...drc/01-09.html > "Ordinary glass is opaque to radiation in the UV-B and UV-C regions" but will transmit 90% in the black-light UVA range.

From other reading in the last few minutes, it's nearly impossible to get sunburned through an automobile windshield, easier through the side windows.

So, don't worry about your eyes while driving? Or indoors. Which leaves ummm how much time spent outside?
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Old 6th June 2010, 07:27 PM   #8
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I don't know anything about home UV testing, but polycarbonate plastic -- used for safety glasses, break-resistant lenses in regular glasses, bulletproof teller windows, etc. -- blocks almost all UV light. When I need sunglasses, I often buy tinted safety glasses at places like Home Depot. They are made of polycarbonate, they have to meet federal (ANSI) standards, they usually wrap around your eyes (giving you more protection), they're sturdy, and they're cheap -- as little as five or six bucks. (Of course, they don't say Gucci or Prada, but then when you lose them you don't kick yourself.)

http://www.allaboutvision.com/lenses/polycarb.htm

Also possibly helpful:
http://www.straightdope.com/columns/...traviolet-rays
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Old 6th June 2010, 07:42 PM   #9
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Here's the link to the article about sunglasses that don't block most UV light - http://news.yahoo.com/s/livescience/...msstudyreveals

Thanks for the advice. I'll see if I can borrow the UV light and look for something fluorescent, or even invest in a UV meter if I can find one that is cheap enough.
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Old 6th June 2010, 10:16 PM   #10
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Originally Posted by Zelenius View Post
Here's the link to the article about sunglasses that don't block most UV light - http://news.yahoo.com/s/livescience/...msstudyreveals
Thanks for the link. I'll have to reference this thread the next time a free market fanatic tries to explain how efficient industries regulate themselves.
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Old 7th June 2010, 06:27 AM   #11
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Originally Posted by casebro View Post
I wonder if Radio Shack sells a UV "photovoltaic cell"? Probably cost $1. That and a voltmeter, and you would have UV meter... Calibrate it in and out of a window.

And Yes, you are right, it's usually the lens material that has the inherent spectrum limitation, NOT the tint. Clear glass blocks UV very well, the amber in beer bottles blocks visible BLUE light, preventing skunkiness. Link: http://realbeer.com/spencer/bottle.html

Plastics I dunno

Radio Shack does sell mini photovoltaic cells. So what you're saying is to connect a voltmeter to a photovoltaic cell, shine a UV light through the sunglasses onto the photovoltaic cell, and if any UV light passes through the sunglasses, the voltmeter will indicate it? Thanks.
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Old 7th June 2010, 08:03 AM   #12
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Originally Posted by Zelenius View Post
Radio Shack does sell mini photovoltaic cells. So what you're saying is to connect a voltmeter to a photovoltaic cell, shine a UV light through the sunglasses onto the photovoltaic cell, and if any UV light passes through the sunglasses, the voltmeter will indicate it? Thanks.
Don't bet on it. PV-Cells respond best in red to orange light (Scientific American.)

Last edited by MortFurd; 7th June 2010 at 08:05 AM.
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Old 12th June 2010, 05:22 AM   #13
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Last edited by Ladewig; 12th June 2010 at 05:37 AM.
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Old 12th June 2010, 08:28 AM   #14
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There are hordes of UV testing cards out there, most of them fairly inexpensive.

UV filtration is no big deal. Ordinary glass drops about 95% of it. I always giggle at how optical windows are sold to camera people as 'UV Filters' when what they are used for is to protect the front lens.

A couple of decades ago, a 'Only seen on TV' commercial for cheap sunglasses tried to imply that regular sunglasses don't block the UV. They do, actually. It was a wonderful bit of deceptive advertising.
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