Ambrotype

An ambrotype is a photograph in which a weak negative on glass appears positive against a dark background. The image consists of silver in a collodion layer. It is a direct image on the plate, not an ordinary paper photograph mounted behind glass.

The background may be dark varnish or a dark material behind the glass. Portraits were often placed in small cases or frames, and some were hand-coloured. A hinged case alone does not identify the process: several early photograph types could have similar housings.

Common confusions

A tintype uses iron rather than glass as its support. A daguerreotype has a different structure with a silver-plated copper support. Ambrotypes and tintypes can be difficult to distinguish when the support is concealed. A modern paper photograph of an ambrotype is a reproduction, not the original plate.

Documentation and handling

Do not remove the plate from its case merely to identify the material, or touch the image surface. The glass can break and the surface is vulnerable. Retain the housing, inscriptions and known family history as part of its provenance.

Practical example: photograph an open portrait case without loosening the plate, and record inscriptions separately. Also consider light damage. Seek professional assessment of uncertain processes or damage before cleaning.

To offer older photographs for sale, send OBA images and known background information.