Until the ambrotype came along in 1851, when an Englishman named Frederick Scott Archer developed an inexpensive technique to expose photographic images on thin sheets of glass, the daguerreotype was the only type of photograph available. Made of copper plates faced with silver, daguerreotypes were expensive and fragile, which is why they were housed in sealed cases to keep their polished surfaces from tarnishing due to contact with fresh air.
In 1854, an American named James Cutting filed three patents for new ambrotype processes—in a curious footnote, Cutting changed his middle name from Anson to Ambrose, perhaps to more closely associate himself with ambrotypes in the same way that Louis-Jacques-Mandé Daguerre was linked by his name to daguerreotypes. Like daguerreotypes and some of the tintypes that came a bit later, ambrotypes were also cased to protect them. It’s not that their surfaces were as sensitive as those of daguerreotypes. Rather, it was the glass ambrotype itself that was at risk.
Hinged cases, usually made of wood and covered in leather, did the trick. The ambrotype was placed within this case in layers, somewhat like a sandwich. There was the ambrotype (with or without a black background, which was required to keep the image from resembling a negative), topped by a layer of brass matting to frame the image and protect it from another layer of glass on top of that. Holding these pieces together was the preserver, also made of brass, all of which was then secured in the case, which was lined with velvet or silk.
The heyday of ambrotypes in the United States was brief, from 1854 to 1865, when uncased tintypes took over. Since early tintypes were also cased in the same way as daguerreotypes and ambrotypes, and because ambrotypes and tintypes look quite similar because they use the same collodion and silver solution to expose the photograph, ambrotype collectors will sometimes place a magnet on a cased photo—if it stays put, then the image behind the glass is a tintype.
Cases are a good way to date an ambrotype, daguerreotype, or tintype. Wood cases were used from roughly 1840 to 1865. While the vast majority of these were covered in leather, some were covered in paper. In both examples, the cases were decorated (often only on the front) and then shellacked or varnished. Beginning around 1856, thermoplastic Union Cases, so-named for the way in which heated shellac made a “union” with its wooden base, were introduced by Samuel Peck. A couple of years later, in 1858, the fronts and backs of wood cases were also produced from pressed wood chips or papier-mâché. These cases featured embossed designs on their fronts, although the relief was not as deep as on the Union Cases.
The liners inside the cases can also help you date an ambrotype. Early liners were made out of plain silk, while those from 1845-on were made of velvet, often embossed with floral or other designs. By 1855, photo studios and case makers were adding their names, and even their addresses, to the embossed image. The brass mats inside the sandwich offer different clues. For example, oval mats were used throughout the era of cased photos, with octagon mats used early and ornate shapes generally coming later. Surface textures on the mats ranged from pebbly and sandy to smooth, while stamped and foil-like mats were in vogue toward to end of the case era (patriotic stamped designs were, of course, popular during the Civil War). As with the mats, preservers got more ornate the closer you get to 1865.
As for the glass bearing the image, these included double-pane glass (one of Cutting’s patents), a purplish-black “ruby” glass, and thin single panes of clear glass, whose backs were either painted with pitch or backed with black cloth or paper. Double-pane glass was used from 1854 to 1858, single sheets were in vogue from 1856 to 1864, and the ruby glass appeared around 1857.