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Variant of the wet plate collodion process

The ambrotype, also known as a collodion positive in the UK, is a positive photograph on glass made by a variant of the wet plate collodion process.

Following the invention of daguerreotypes, cheaper than the French invention, 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.

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 During the 1860s it was superseded by the tintype, a similar photograph on thin black-lacquered iron, hard to distinguish from an ambrotype if under glass.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

Process

One side of a clean glass plate was coated with a thin layer of iodizedcollodion, then dipped in a silver nitrate solution. The plate was