Optics & Photonics News

The wet-plate collodion process, invented by Frederick Scott Archer in 1851, was the method for making the types of photographs popular during the American Civil War.

Early types of positive prints

In the 1840s and 1850s, as politicians in the North and South hotly debated the issues leading up to the Civil War, Americans were introduced to the first popular type of photography: the daguerreotype.

Named for French inventor Louis Daguerre, the daguerreotype’s substrate, canvas or “film” was a silver-coated copper plate exposed to iodine fumes, then placed in the back of a camera and illuminated. When subsequently exposed to the fumes from heated mercury, the latent image would emerge as the silver would adhere to the regions of the plate that were exposed to light. The result was a unique, detailed positive print that could be seen only from certain angles.

Daguerreotypes fascinated Americans of the mid-19th century, and many of the photographers who would later chronicle the American Civil War got their start in the business making them. In major cities, the public flocked to galleries to see portraits of famous people. In the 1850s, the expense and impracticality of daguerreotypes led to their replacement by new types of photographic processes: the calotype, the ambrotype, the tintype (also known as the ferrotype) and the albumen print.

The calotype process uses silver-salted paper to make a
paper negative. In theory, one could make a large number of
positive copies by contact-printing the
negatives onto other sheets of light-sen-
sitive paper. In practice, calotype prints
lacked some of the fine detail of daguerre-
otypes. Also, sometimes the texture of
the negative paper would leave unwanted
marks on the positive print.

Wet-plate collodion process

The wet-plate collodion process, invented by Frederick Scott Archer in 1851, was the method for making the types of photographs popular during the American Civil War. The difference was in the substrate: ambrotypes, as well as commercial portrait and landscape prints, required glass-plate negatives, while tintypes were printed on black-lacquered iron (not tin).