A photograph is the result of a unique set of choices the artist makes. One of the most important decisions involves what materials (or mediums) to use when printing. Photographers employ different kinds of surfaces—metal, paper, glass, and flexible film—that are treated with light-sensitive chemicals to record images. These chemicals affect surface texture, sharpness of detail, color, and tone. Two of the first types of photographic mediums to gain prominence were daguerreotypes and salted paper prints.

Daguerreotypes

Popular from 1839 until about 1860, daguerreotypes were named for their French inventor, Louis-Jacques Mandé-Daguerre (1787–1851). His process formed highly detailed images on a sheet of copper, very thinly plated with silver and sealed behind glass. Portrait of Edgar Allan Poe (shown below), exemplifies the ability of daguerreotypes to depict a singular, nuanced impression, for which the images were particularly prized.
Portrait of Edgar Allan Poe, late May–early June 1849, unknown photographer. Daguerreotype; 4 13/16 inches high x 3 1/2 inches wide (The J. Paul Getty Museum, 84.XT.957)
The process of making daguerreotypes began with an extremely thorough cleaning and polishing of the silver-plated sheet. Next the shiny plate was suspended over iodine in a closed container. Rising vapors from the iodine would unite with the silver to produce a light-sensitive surface coating of silver iodide. The sensitized plate, inside a lightproof holder, was transferred to a camera and, in the earliest days, exposed to light for as long as twenty-five minutes. The plate was then developed by placing it in a container suspended over a heated dish of mercury, the vapor from which reacted with the exposed silver iodide to produce an image in an amalgam of silver mercury. The image was fixed (made permanent) by immersion in a solution of salt or hyposulfite of soda, and toned with gold chloride to improve its color, definition, and permanence. Information on Daguerre’s technique quickly spread from country to country. As the public became captivated by the sensation of seeing portraits that appeared more lifelike than painted or drawn images, daguerreotype studios soon sprung up across Europe and the United States.
Highly vulnerable to physical damage from abrasion and chemical damage from tarnishing, daguerreotypes were usually protected with a metal mat and a covering sheet of glass. This construction was then sealed with tape and fitted into a book-like case made of leather-covered wood or an early form of plastic (compressed sawdust and resin). Cases were often lined with dark velvet (shown below). As the finished daguerreotype image lies on the surface of a highly polished plate, it must be held at an angle to minimize reflections. The experience of viewing a daguerreotype is intimate. Holding this image of Poe gives the sensation of staring directly into his eyes, yet the surface of the plate is mirrored so you see yourself staring back.
Portrait of Two Uniformed Men (Two Travelers), 1852–55, John Frederich Polycarpus von Schneidau. Half-plate daguerreotype image; (inside mat) 4 1/2 inches high x 3 5/16 inches wide, (case, closed) 6 inches high x 4 3/4 inches wide (The J. Paul Getty Museum, 84.XT.1565.29)
The lifelike detail that daguerreotypes offered was well suited for portraiture, and the rich, black tones and mirror-like surface facilitated a sharp, positive image. Grayish-white tones were often modified with delicate application of color, heightening the image’s sense of realism. Refinements of technique and equipment considerably reduced exposure times and made the daguerreotype wildly popular until the middle of the 1850s, despite its relative expense.

Negative-positive photography: salted paper prints

William Henry Fox Talbot (1800–77) developed a process that produced a paper negative, from which photographic images on paper were printed. Popular until roughly 1860, early paper prints were made on high-quality writing paper, which gave the prints a matte surface with visible paper texture (shown below). During this time, photographers who created paper photographs using negative-positive techniques competed with daguerreotype photographers for attention. Although daguerreotypes were more detailed, they had to be made one at a time and were each unique. The process introduced by Talbot offered the opportunity to produce multiple prints from a single negative.
Carriages and Parisian Town Houses, 1843, William Henry Fox Talbot. Salted paper print from a paper negative; 6 5/8 inches high x 6 13/16 inches wide (The J. Paul Getty Museum, 84.XM.478.6)
In the early 1840s, Talbot refined a negative-positive process that produced photographic images on salted paper. Now generally referred to as a salted paper print, it was made by sensitizing a sheet of paper in a solution of salt (sodium chloride), and then coating it on one side with silver nitrate. Light-sensitive silver chloride formed on the paper. After drying, the paper was put sensitive side up directly beneath a negative (an image in which the lightest areas of the photographed subject appear darkest and the darkest areas appear lightest) and under a sheet of glass in a printing frame. This paper-negative-glass sandwich was exposed, glass side up, outdoors in sunlight. The photographer determined the length of exposure, up to two hours, by visual inspection. When the print had reached the desired intensity, it was removed from the frame and fixed with sodium thiosulfate—at that time called hyposulfite of soda (“hypo”)—which stopped the chemical reactions. It was then thoroughly washed and dried.
The Letter, 1843–47, David Octavius Hill and Robert Adamson. Salted paper print; 8 inches high x 5 5/8 inches wide (The J. Paul Getty Museum, 84.XM.966.10)
The use of sodium chloride (table salt) and silver nitrate encouraged a warm color range, from reddish brown to purplish grey, and shadows were soft (shown at the left). The print could be toned with gold chloride for greater permanence and richer tone. A finished salt print is subdued in tone, reddish brown in color, and has no surface gloss. If toned, it is purplish brown; if faded, yellowish brown. Its highlights are usually as white as its paper support.
Daguerreotypes and salted paper prints were popular throughout the mid-1800s, but neither was able to fully eclipse the other. The daguerreotype process offered higher resolution, while the negative-positive process offered reproducibility. One was hand-held, while the other could be easily mailed or included in books. As further experimentation with photographic media advanced, photographers continued to seek methods that would combine and extend the best features of each practice. Both daguerreotypes and salted paper prints, though still created periodically, were supplanted by albumen silver prints, a new photographic medium of choice.

Resources
Adapted from Looking at Photographs: A Guide to Technical Terms by Gordon Baldwin. Los Angeles: J. Paul Getty Museum, 1991.
Learn more about the daguerreotype process in the video Early photography: making daguerreotypes.