An ordinary ambrotype is a photograph made using a collodion (cellulose nitrate) binder on a glass support. The resulting image is actually white, so it looks like a negative. In order for the image to look like a positive, the back of the glass is coated with a dark paint or lacquer or a piece of dark paper or fabric is put behind it.
I knew the one ambrotype that I purchased was a typical ambrotype, since I could see where some of the lacquer was chipped off. The other ambrotype, I really liked the image, and I had a feeling that maybe it was a ruby ambrotype. A ruby ambrotype doesn't need black lacquer or black paper or anything because it was made on a sheet of dark glass.
I dismantled everything once I returned home, to my mini-suction cup. Somebody had attached dark fragments from 35mm film rolls on the back with like medical tape. On September 22, 2006. Which was interesting. I decided to remove it (for a couple reasons, one on which is that it is my object now - ha!). It didn't need anything black behind it anyway, because it was a ruby ambrotype. I could tell as soon as I removed the brass frame - I could see the edge of the glass.
Sweet! (The circle in the middle is my camera lense reflecting off the glass). My classmate Lisa analyzed a bunch of these during our second year in school, and it turns out that the compound used to make this color is manganese.
You were so worth that $30 Creepy-Eyed Dude.