In my building, there are ceiling and wall fixtures that use fluorescent bulbs. The cover of them is just a sheet of glass and there is a large square in the middle that is painted white. My question is, does the painted side go toward the bulbs or is the painted side supposed to be pointed toward the outside, away from the bulbs?
I have seen a coat of semi-translucent paint on the inside of a fixture before. My understanding was that the paint was to help dim the direct brightness of the bulb by making the cover more opaque. The paint was put on the inside to help prevent it being worn away, which is how I would place the glass. I've seen the paint chipped off the glass before, and putting it towards the bulb may help prevent this. (plus its easier to clean and looks better?)
I have never seen "inward" paint on a fixture before, flat cover or otherwise. This is interesting. I do think you should flip one around and observe the difference. Just thinking from a physical viewpoint, I would imagine it would create a very slight difference (inward being duller) in the ambiance of the light...though I doubt the "central" block of the light would change much other than the universal dullness achieved by the inward facing paint. Of course none of this takes into account the type/transparency of the paint, glass, fixture, etc. Interesting nonetheless.
Source: lots of google searching and personal contemplation.