Ambrotype is wet plate collodion process on glass that is backed with black paint. The glass plate was actually in the camera, while being exposed and processed. It is not printed on glass. This makes every ambrotype unique and special. In museums are many ambrotypes even 150 years old in perfect condition and also this ambrotype was made by museum standards. The ambrotype is varnished with traditional sandarac varnish. You can see the making of video while I was working on this ambrotype (LINK). The ambrotype is in a handmade wooden case and fastened with wires.