So I have this piece of art on the wall with a lot of bright color, and I want to protect it from fading. On the wall 90 degrees away from the wall hanging, I have two glass balcony doors and 3 skylights above them. Direct sunlight never falls on the art: I do get a little sliver of direct sunlight in the morning the falls on the wall next to it.
But a lot of reflected light makes it in through all that window area. Is putting a UV-filtering window treatment (an adhesive film) on them worthwhile? Am I picking up as much scattered UV as I am other wavelengths?
I have a couple of incandescent floods lighting the art, and I have put a UV filter in front of them. But those wondows would be a lot more hassle, not to mention difficult to do without botching in some way or another.
If you look at direct atmospheric scattering, the amount of scattering increases with frequency, up to the frequencies that are blocked.
[parenthesis]
That’s why the sky is blue. The shorter wavelength part of the spectrum is scattered more by the atmosphere than the longer, so that the from the rays of sunshine passing overhead the blue part gets deflected, while the sunset looks red, for the person standing further to the east…
[/parenthesis]
It sounds however as if you’re ore interested in the scattering from the walls/floors/ceiling. I believe that that depends strongly on the surface coating. I have read about studies done on various paints, but I have no direct knowledge of it. I suppose you could call your interior decorator and ask for the albedo of the paint in the 300nm range.
Popup has it right about scattering (The scattering coefficient goes as the inverse fourth power of the wavelength, so UV light, having shorter wavelengths than visible light, does scatter more). But I don’t know if this will have any measurable difference for your picture protection.
In particular, I’d like to note that virtually all glass and plastic blocks light that has wavelengths of 300 nm or below. Some glasses and plastics start blocking at even longer wavelengths. Light below 300 nm is UV. People vary in their definition of UV, but you can;t push it very far up the scale, because you get into visible light very soon. I’ve always been a bit confused about claims that only certain sunglasse are “UV blockers”. The real trick is to find glass or plastic that will transmit UV.
If you’re worried about your art, by all means get extra protection. It might be the stuff in the low 300s that degrades your work. But most of the UV is alreadsy blocked by your windows plus the glass over your art.
