A process that changed what people expected to see
Before photography, almost every picture was made by hand, and only wealthy people could afford a painted portrait. Within a generation of the announcement of the daguerreotype in 1839, ordinary families were able to buy a likeness of a relative, and newspapers and exhibitions were showing views of distant places and wars. This article is about the nineteenth-century chemistry that made that possible, and the changes in visual culture that followed.
The daguerreotype: a mirror with a memory
A daguerreotype was an image on a silver-coated copper plate, made light-sensitive by fumes of iodine and brought out by mercury vapor. It was extremely detailed, but it was a one-off. It could not be copied, was fragile under its glass cover, and its mirror surface made it awkward to view except at the right angle. Studios appeared in cities across Europe and North America in the 1840s, and portraits were their main business. They were built with large windows and skylights, because electric lighting was not yet practical for the purpose. Mercury vapor was a health hazard for photographers, which is well documented.
Glass negatives
Photographers wanted both the detail of the daguerreotype and the copying ability of William Henry Fox Talbot’s paper negatives. Glass offered a solution. It is transparent, smooth and chemically inert. In 1851, the English sculptor Frederick Scott Archer published the wet collodion process. The steps went roughly like this:
- A glass plate was coated with collodion, a syrupy solution made from guncotton (cellulose nitrate) dissolved in ether and alcohol, containing iodide salts.
- The plate was dipped in a silver nitrate bath to form light-sensitive silver iodide in the collodion film.
- While still damp, the plate was loaded into the camera and exposed.
- It was developed at once, typically with an iron-based developer, and fixed.
- The negative was then used to print positives on albumen paper, made with egg white, which gave fine detail.
The speed and sharpness of the result made it the dominant process for about thirty years. The need to work while the plate was wet meant that outdoor photographers carried a portable darkroom, often a tent or wagon. Some of the chemicals, such as ether, were flammable and required care.
Cheap portraits: cartes de visite and tintypes
Collodion also produced cheaper types of photograph. In the ambrotype, a thin negative on glass backed with black looks like a positive. In the tintype, also called ferrotype and introduced around 1856, the collodion was coated on a thin sheet of iron. Tintypes were inexpensive and durable, and were sold by street photographers and at fairs.
The carte de visite, patented in 1854 by the French photographer Andre Adolphe-Eugene Disdéri, placed several small portraits on one plate, reducing the cost per print. They were mounted on cards the size of a visiting card, and by the 1860s people were collecting them and exchanging them. Albums for storing these cards became a household item. Having one’s picture taken was no longer reserved for the rich.
Dry plates
The wet process was a nuisance, and the inventors of the 1870s looked for a plate that could be prepared in advance. In 1871, the English doctor Richard Leach Maddox suggested using gelatin to hold silver bromide on the plate. Later improvements, including a heat treatment to increase sensitivity credited to Charles Bennett in 1878, made gelatin dry plates fast enough for practical use. Factories could make them in quantity, photographers could buy them ready, and exposures dropped to fractions of a second. The result was an industry of manufacturing and a hobby for amateurs, which paved the way for George Eastman’s later roll film. This is an early example of industrial chemistry scaling up an invention.
War and news
Photographs began to shape how people understood events. Roger Fenton photographed the Crimean War in 1855, though the slow process meant that he mostly made posed views of camps and landscapes rather than action. During the American Civil War in the 1860s, teams working with Mathew Brady and photographers such as Alexander Gardner photographed battlefields and soldiers. An exhibition of photographs of the dead at Antietam in New York in 1862 reportedly affected viewers deeply, as it showed a reality that engravings had softened.
Printing a photograph in a newspaper was a separate problem, since presses used ink in solid areas. Early papers redrew photographs as engravings. The halftone process breaks an image into dots of varying size. A New York newspaper is reported to have printed a halftone photograph in 1880, and the method became common in print shops over the following decades. Halftones later became the standard for printing photographs in books, magazines and newspapers on presses fed by wood pulp paper.
Science and records
Photographic plates also became recording tools. Astronomers exposed glass plates through telescopes and built sky catalogs that remained in use for generations. Surveyors, archaeologists and police used photographs as records. When Wilhelm Roentgen discovered X-rays in 1895, he recorded the first images on photographic plates, and for years medical X-ray machines produced their pictures on glass or film. Photography also gave researchers a way to freeze fast motion.
Changes in visual culture
The effects were not only technical. People learned to see their own faces and those of distant strangers. Painters reacted in different ways, some adopting photographs as references, others moving away from literal likeness. Debates started about whether photography was art, a question that persisted for decades. The idea that a photograph provides evidence also took hold, though photographers in the nineteenth century already staged, retouched and combined images.
What to keep in mind
Dates for some innovations, such as the first tintype or the first halftone in a newspaper, vary between references. The broad outline, in which glass plates and cheap portraits made photography a mass medium, is well supported.