ambrotype

The ambrotype, also known as a collodion positive in the United Kingdom, is a positive photograph on glass made by a variant of the wet plate collodion process. As a cheaper alternative to the French daguerreotype, ambrotypes came to replace them. Like a print on paper, it is viewed by reflected light. Like the daguerreotype or the prints produced by a Polaroid camera, each is a unique original that could only be duplicated by using a camera to copy it.

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 During the 1860s it was superseded by the tintype, a similar photograph on thin black-lacquered iron, hard to distinguish from an ambrotype if under glass.

The term ambrotype comes from Ancient Greek: ἄμβροτος ambrotos, "immortal", and τύπος typos, "impression".