Does window glass filter out UV light?

[Muse]

I wonder this a lot. I have some items on a ledge in front of my kitchen window and wonder if I shouldn't put plastic items that will degrade from UV light where they'll get the afternoon sun through the west facing windows. The windows in there have been there for probably 30-40 years, maybe more. They're clear "glass." Are any plastic items susceptible to UV damage going to suffer? Is there an easy way I can test this?

 

[Key West]

Plain window doesn't block UV.

You ever walk down shops with showcase windows and the posters inside it has the colors all dulled? That's because of UV.

 

[Mark R]

Glass filters out a lot of UV - but not all. Conventional glass is almost totally opaque to UVB and C. However, it is partially transparent to UVA.

UVA is much less damaging than UVB and C - but is still damaging enough to degrade susceptible materials.

Very suspceptible materials - such as dyes and inks - are actually sensitive to visible blue and violet light - and will be degraded even with total UV block. Museums, archives, rare book shops, etc. - will either board up windows, or place yellow filters in the windows to reduce the amount of blue and UV light coming in to the minimum.

 

[Wyndru]

That sucks, I hope we didn't damage our newborn's skin. This week she was inside in the sun quite a bit, because the doctor said UV rays would not penetrate the panes of glass. She had newborn jaundice, and the doc recommended that we place her in the sun (indoors) each day for a few hours.

 

[Key West]

That sucks, I hope we didn't damage our newborn's skin. This week she was inside in the sun quite a bit, because the doctor said UV rays would not penetrate the panes of glass. She had newborn jaundice, and the doc recommended that we place her in the sun (indoors) each day for a few hours.

god what a dumbass doctor. I wouldn't listen to anything outside of his field. A plain transparent window doesn't block UV ray.

It's a common sense. I got sunburn on my left arm just from being in my friend's car even with 5% factory tint.

 

[Mark R]

That sucks, I hope we didn't damage our newborn's skin. This week she was inside in the sun quite a bit, because the doctor said UV rays would not penetrate the panes of glass. She had newborn jaundice, and the doc recommended that we place her in the sun (indoors) each day for a few hours.

Some do penetrate - but a lot of UV is filtered out (practically all of the more harmful UV is filtered). You can't get tanned or sun-burned behind glass - even if you lie directly under a window, because the glass filters out so much UV that you can't get a harmful dose of it.

It's unlikely that even new-born skin is delicate enough to be harmed by the filtered light behind glass. And the visible blue light may have done good by degrading the jaundice toxin (which is a yellow dye - and like other dyes is degraded by blue light).

 

[Key West]

Some do penetrate - but a lot of UV is filtered out (practically all of the more harmful UV is filtered). You can't get tanned or sun-burned behind glass - even if you lie directly under a window, because the glass filters out so much UV that you can't get a harmful dose of it.

It's unlikely that even new-born skin is delicate enough to be harmed by the filtered light behind glass. And the visible blue light may have done good by degrading the jaundice toxin (which is a yellow dye - and like other dyes is degraded by blue light).

Then explain my post above.

 

[Wyndru]

Some do penetrate - but a lot of UV is filtered out (practically all of the more harmful UV is filtered). You can't get tanned or sun-burned behind glass - even if you lie directly under a window, because the glass filters out so much UV that you can't get a harmful dose of it.

It's unlikely that even new-born skin is delicate enough to be harmed by the filtered light behind glass. And the visible blue light may have done good by degrading the jaundice toxin (which is a yellow dye - and like other dyes is degraded by blue light).

I hope that's the case, thanks for the info.

Oh, and sorry for the threadjacking OP, I basically spit out my coffee when I saw the replies about UV making it through glass.

 

[Muse]

Glass filters out a lot of UV - but not all. Conventional glass is almost totally opaque to UVB and C. However, it is partially transparent to UVA.

UVA is much less damaging than UVB and C - but is still damaging enough to degrade susceptible materials.

Very susceptible materials - such as dyes and inks - are actually sensitive to visible blue and violet light - and will be degraded even with total UV block. Museums, archives, rare book shops, etc. - will either board up windows, or place yellow filters in the windows to reduce the amount of blue and UV light coming in to the minimum.

This is the most knowledgeable post. I just read a lot of the Wikipedia article on Ultraviolet. Well written and extensive:

http://en.wikipedia.org/wiki/Ultraviolet

I'm still not sure about putting plastic items in front of those windows. I think the answer may be that they're ~90% protected, but not totally protected, something fuzzy like that.

 

[Muse]

I hope that's the case, thanks for the info.

Oh, and sorry for the threadjacking OP, I basically spit out my coffee when I saw the replies about UV making it through glass.

No problem. You might want to read that Wikipedia article I linked in the last post. It will probably ease your anxiety considerably. IMO, your doctor probably knows what he/she is talking about in terms of that recommendation.

 

[Key West]

No problem. You might want to read that Wikipedia article I linked in the last post. It will probably ease your anxiety considerably. IMO, your doctor probably knows what he/she is talking about in terms of that recommendation.

Hm. Can you explain my experience if conventional glass blocks UV rays?

*All movie posters behind a glass are faded after prolonged exposure
*I was in my friend's car in the backseat with windows up and AC up. My left arm was on the arm rest exposed to the sun. The drive was about 3 hours. I got a mild sunburn on that arm and nowhere else. I was also not out for the rest of the day.

 

[Colt45]

It blocks the strong stuff at least, UVC. probably somewhat less effective the closer you go to visible light.

Otherwise you'd get sunburn from fluorescent lights (the quicksilver gives off UVC when ionized), I would think, although I suppose the phosphor alone would stop a fair bit...

Here's an old mercury arc rectifier, good for an arse-ton of current (DC trains and all sorts of stuff like that were originally powered via these things). Anyway, if the glass didn't block the UV, it would ah heck your eyes.

IIRC, the UV fluoro tubes (for germicide, erasing EPROM, etc) use fused quartz envelopes, specifically because it can pass UV, whereas normal glass cannot, or at the least very poorly.

 

[ElFenix]

Hm. Can you explain my experience if conventional glass blocks UV rays?

*All movie posters behind a glass are faded after prolonged exposure
*I was in my friend's car in the backseat with windows up and AC up. My left arm was on the arm rest exposed to the sun. The drive was about 3 hours. I got a mild sunburn on that arm and nowhere else. I was also not out for the rest of the day.

if you'd have been exposed to full sun for 3 hours you'd be scraping your skin off that arm rest.

 

[Key West]

if you'd have been exposed to full sun for 3 hours you'd be scraping your skin off that arm rest.

Not really. I have olive skin and am out on the beach without sun block for much longer than that.

Now to on-topic:

1. OP's doc says 'leave baby on direct sunlight for couple hours under windows cuz UV is blocked'

2. That's enough to give me a burn on my adult skin. Would you do that to your baby?

3. Doctor was wrong. I sure wouldn't leave my baby in direct sunlight for several hours a day because it's shielded by plane glass.

 

[zCypher]

if you'd have been exposed to full sun for 3 hours you'd be scraping your skin off that arm rest.

I spend most of my time indoors, am not dark skinned, and I spent several hours in the sun two days during this past week without even burning at all. Something tells me that scraping your skin off the arm rest is slightly exaggerated, just slightly. lol

 

[uclaLabrat]

Normal glass (borosilicate and the like) has a UV cutoff at about 300 nm or so, so UV above that passes just fine. Quartz has a UV cutoff somewhere in the 200-220 nm range IIRC, so it is used in things like mercury lamps (UV peak at 254 nm) for photolysis or whatever.

 

[Muse]

Hm. Can you explain my experience if conventional glass blocks UV rays?

*All movie posters behind a glass are faded after prolonged exposure
*I was in my friend's car in the backseat with windows up and AC up. My left arm was on the arm rest exposed to the sun. The drive was about 3 hours. I got a mild sunburn on that arm and nowhere else. I was also not out for the rest of the day.

As mentioned above, inks are extra sensitive.

As also mentioned above, the blockage of UV by window glass isn't entire. Read the linked Wikipedia article for technical details. Some UV got through the window, enough to sunburn your arm some. If the window had been open the burn would have been much worse.

 

[matas]

oh so you do get tan through a window(glass).