Ambrotypes
The ambrotype is a positive photograph on glass and is a variation of the wet plate collodion process. Like a print on paper, it is viewed by reflected light. Each print is a unique original. The ambrotype was introduced in the 1850s. During the 1860s it was superseded by the tintype, a similar photograph on thin black-lacquered iron, hard to distinguish from an ambrotype if under glass.