Values for the light transmittance of glass I would like to ask if somebody knows where is it possible to find percentages for light transmittance of different unusual glasses such as matte, glossy, stained glass, etc.?
 A: A partial answer, which I will try to expand later.
There is a PDF file at Pilkington Glass which runs to 200 pages. 
but scroll down about 15 pages to their stats for each glass type.
I would then suggest you keep a note of the different glass names and go to the Pilkington main site and see what their glass samples actually look like.
Best of luck with it.
A: Glass transmission is characterized by how much light, at a particular wavelength, passes through an uncoated, plane parallel piece of that glass of a specific thickness. Got that? Whew! The types of glass you are speaking of, matt, glossy, stained etc., have nothing to do with basic glass transmission because in your case, it's not the glass that is affecting the transmission but the surface treatment or bulk properties (stained glass). Schott Glass has a catalog on stained glass and gives those transmissions, but for other things like frosted glass, translucent glass etc, you need to get specific. Did this glass come from a particular manufacturer? If so, then you need to call them up to see what type of glass is used (Bk7 etc.), and what how their surface treatments affect transmission (usually scatter or absorption). When light enters a piece of glass, you typically get a Fresnel reflection off of each surface, some absorption in transmission, and some scatter from each surface due to rms surface roughness. The actual TRANSMISSION usually accounts for Fresnel reflection and absorption only, not scatter. I hope this helps. You need to break down your question and really define what you have, what you want to learn about it and so forth. If someone just took sandpaper to a glass window, then there will not be any specs on transmission with that scatter taken into account.
