Ambrotype

The ambrotype is a direct-positive photographic process, adapted from the wet collodion process, in which a glass plate is deliberately underexposed to produce a pale negative image. When that glass plate is backed with a dark material such as black varnish, paper or velvet, the pale negative image reads to the eye as a positive photograph. Ambrotypes largely displaced the daguerreotype during the 1850s because they were cheaper and faster to produce and, unlike a daguerreotype's reflective metal surface, did not need to be tilted at a precise angle to be seen clearly, though like the daguerreotype each ambrotype remains a single unique image on its own glass plate rather than a print made from a reusable negative. In 1854, James Ambrose Cutting of Boston took out several patents on the process, and by the late 1850s the ambrotype had overtaken the daguerreotype in popularity before itself being displaced by the tintype during the 1860s.