# Glass that keeps pictures from fading in the sun **URL:** \ **Category:** Factual Questions\ **Created:** [December 14, 2021, 7:31pm UTC](https://boards.straightdope.com/t/glass-that-keeps-pictures-from-fading-in-the-sun/956068 "2021-12-14T19:31:51Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [December 14, 2021, 7:31pm UTC](https://boards.straightdope.com/t/glass-that-keeps-pictures-from-fading-in-the-sun/956068/1 "2021-12-14T19:31:51Z")
Is there a way to tell if the glass over a painting is the UV blocking glass? Something that can be done from home without taking it to a frame shop to check? May require some specialized equipment to look at the light spectrums coming through the glass I think. But maybe there is a simple way. Thanks. ---
**Author:** ![racer72](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/racer72/32/3075_2.png) [@racer72](https://boards.straightdope.com/u/racer72)\ **Post date:** [December 14, 2021, 7:55pm UTC](https://boards.straightdope.com/t/glass-that-keeps-pictures-from-fading-in-the-sun/956068/2 "2021-12-14T19:55:43Z")
Glass should never be placed over most paintings, especially oil paintings. Saw this on an episode of Antiques Roadshow. A woman had a painting from the 1850’s that had been placed under glass in the 1930’s. The glass ruined the brush strokes in some areas, in other areas, the glass caused heat to build up and caused the paint to melt. Her potential $5000 painting was worth about $600. The appraiser said the painting could possibly be restored but will never be worth it’s true value. [Here is a site](https://framers.com/picture-framing-glass-types/) that should have all the info you need. ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [December 14, 2021, 8:03pm UTC](https://boards.straightdope.com/t/glass-that-keeps-pictures-from-fading-in-the-sun/956068/3 "2021-12-14T20:03:37Z")
> [@racer72](#): > > Glass should never be placed over most paintings, especially oil paintings. Saw this on an episode of Antiques Roadshow. A woman had a painting from the 1850’s that had been placed under glass in the 1930’s. The glass ruined the brush strokes in some areas, in other areas, the glass caused heat to build up and caused the paint to melt. Her potential $5000 painting was worth about $600. The appraiser said the painting could possibly be restored but will never be worth it’s true value. But your example doesn’t pertain to UV protected glass at all. There isn’t any evidence that UV glass, with proper side ventilation, will damage a painting. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [December 14, 2021, 8:28pm UTC](https://boards.straightdope.com/t/glass-that-keeps-pictures-from-fading-in-the-sun/956068/4 "2021-12-14T20:28:36Z")
> [@enipla](#): > > Is there a way to tell if the glass over a painting is the UV blocking glass? Something that can be done from home without taking it to a frame shop to check? > > May require some specialized equipment to look at the light spectrums coming through the glass I think. But maybe there is a simple way. > > Thanks. You’ll need a **[black light (i.e. a UV source)](https://www.amazon.com/s?k=black+light&ref=nb_sb_noss_2)** and some **[fluorescent paper](https://www.amazon.com/s?k=fluorescent+paper&ref=nb_sb_noss_1)** (i.e. paper that emits visible-wavelength light when illuminated with UV). In a dark room, shine the UV light directly at the paper and get a sense of how bright the paper is. Now put the paper behind the glass, light it up, and see how bright it is (or isn’t). The darker it is, the less UV light is getting through the glass to make the paper fluoresce, at least for the particular wavelength(s) being emitted by your chosen source. Anything more rigorous than that would require knowledge of what wavelengths are being emitted by your source, and a sensor that can measure irradiation as a function of wavelength. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [December 14, 2021, 10:43pm UTC](https://boards.straightdope.com/t/glass-that-keeps-pictures-from-fading-in-the-sun/956068/5 "2021-12-14T22:43:21Z")
Machine\_Elf - that’s a bit more than I want to dig into. But was curious if there was a simple test. Cool test though. Had black light posters a… umm… few years ago. So I do understand your explanation. And interesting Racer72. Oil paints, probably really, really never ‘dry’ or fix. ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [December 15, 2021, 7:02am UTC](https://boards.straightdope.com/t/glass-that-keeps-pictures-from-fading-in-the-sun/956068/6 "2021-12-15T07:02:56Z")
I asked a somewhat related question earlier in the year. I still have the posters in hiding. > [@Household UV-blocking glass testing](https://boards.straightdope.com/t/household-uv-blocking-glass-testing/931739): > > I’ve got some posters that are matted and under glass. However, I don’t know if the glass has anti-ultraviolet light properties and I don’t want to display them until I’m sure they’re safe. Is there a way I can test with household items? ---
**Author:** ![Kent\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kent_clark/32/105_2.png) [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)\ **Post date:** [December 15, 2021, 4:19pm UTC](https://boards.straightdope.com/t/glass-that-keeps-pictures-from-fading-in-the-sun/956068/7 "2021-12-15T16:19:25Z")
Nevermind ---
**Author:** ![garygnu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garygnu/32/2924_2.png) [@garygnu](https://boards.straightdope.com/u/garygnu)\ **Post date:** [December 15, 2021, 8:01pm UTC](https://boards.straightdope.com/t/glass-that-keeps-pictures-from-fading-in-the-sun/956068/8 "2021-12-15T20:01:58Z")
I worked as a picture framer so long I could tell just by looking at the glass. Not that it’s hard to see, the UV coating has a distinctive sheen to it. However, that side is normally placed on the inside, but you can still see it from the correct angles. Ar a very low angle it should have a very slight rainbow effect. UV plexiglass is more difficult to ID, but it, too, has a peculiar look to it. One unlikely solution is sometimes a promotional sticker for the UV glass brand is placed on the back of the frame job. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [December 15, 2021, 8:40pm UTC](https://boards.straightdope.com/t/glass-that-keeps-pictures-from-fading-in-the-sun/956068/9 "2021-12-15T20:40:31Z")
Thanks Gary. I think it has a sheen. I will look.