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In the mid-1850s, American photographers, from the celebrated Mathew Brady to the little-known itinerant LWF Mark, embraced a new photographic medium known as the ambrotype. Taking its name from the Greek ambrotos (meaning immortal or improverished) and typos (image or impression), an ambrotype was created when an underexposed collodion negative on glass was made to appear as a positive image when viewed against a dark background.
The process that made the ambrotype possible was formulated in 1851 by Englishman Frederick Scott Archer, who discovered that a syrupy mixture of collodion (guncotton dissolved in ether and alcohol) and potassium iodide could be flowed over a glass plate to create an emulsion. This emulsion was then made light sensitive by immersing the plate in a bath of silver nitrate. If the sensitized plate was placed in a camera while still damp, exposed, and then immediately developed, fixed, and washed, the result was a milky-toned negative on glass. Although this process allowed photographic images to be printed on paper, many photographers initially adopted it to create positive pictures on glass.
The ambrotype was introduced in the United States in 1854, where aspects of its production were governed by patents issued to James A Cutting. Many photographers paid licensing fees to Cutting, whose name appears on the brass mats of countless American ambrotypes. Cheaper to produce than daguerreotypes and packaged in attractive presentation cases, ambrotypes remained popular in this country for nearly a decade. |