Photography Collection at Georgetown University Library

The English scientist William Henry Fox Talbot (1800-1977) developed salted paper prints, essentially a “printing-out” process, in 1834-35, and it became widely available by 1839. The salted paper technique was initially used to create his sunlight exposed drawings known as “photograms," made by placing feathers, lace or other materials onto paper treated  with silver chloride and exposing it in ultraviolet light. After processing, the image resulted in a negative where the feather had blocked the effects of the light on the paper. The related technique known as calotype or talbotype created a translucent paper negative that could produce multiple positive images from simple contact printing. Calotype differed from salted paper in the chemicals employed (silver iodide, with acetic and gallic acid) and the physical process, which was developed-out instead of printed-out. 

Using paper as a negative resulted in a slightly grainy of fuzzy effect as the paper fiber blurred the image. By 1855, calotype fell out of use as tastes shifted towards the glossier paper and sharper focus images of albumen prints.

The platinum process was patented in 1873 by the British inventor William Wills, and further developed by 1879 when he established the Platinotype Company that made prepared printing papers commercially available.The platinum process is relatively simple but involves complex chemical interactions. The chemistry is based on the light sensitivity of a compound known as ferric (or iron) oxalate. It becomes reduced in ultraviolet light to a ferrous oxalate and reacts with platinum to reduce it to elemental platinum, or palladium. Paper is coated with these chemicals and the exposed image made from contact with a negative is held in the metal fibers embedded in the paper. These prints are therefore less sharp overall and have a matte finish. By varying the amount of platinum and the addition of varying oxidizing agents, these prints can range in tone from a warm sepia to a cool purple-black, and no two prints are exactly the same. Platinum is one of the most durable of metals and platinum prints have the longest lifespan of any photographic media. By the time of World War I, however, platinum came in high demand for war production rendering it more scarce and expensive. The gelatin silver process gradually supplanted the use of platinum in printing papers, and by 1937 the Platinotype Company closed.

The process of albumen prints, or albumen silver prints, was published in 1847 by Louis Désiré Blanquart-Evrard and soon became the most commercially-viable means of capturing a photographic image on paper from a negative. The paper was coated with a solution of albumen (found in egg white), sensitized with silver nitrate, and used primarily with wet-plate collodion negatives and for a short time with dry-plate negatives. Popular throughout the second half of the nineteenth century, albumen prints have a characteristic warm tonality and were commonly used in cartes de visites, portraits of famous people mounted onto cards that were popularly sold, traded, and collected in Victorian photo albums.

Most twentieth-century black and white photographs are gelatin silver prints. They rely on the special properties inherent in baryta paper, which became available to the public around 1900 through the Eastman Kodak Company. Baryta paper has a coating of white pigment mixed with gelatin. The pigment coating allows the developed image to be sharper in focus, with greater detail visible. In the gelatin silver process, a solution of silver salts suspended in gelatin is applied to the baryta paper and exposed in a darkroom to ultraviolet light through a negative. The paper is developed-out through immersion in chemicals, then rinsed and dried.

Digital photography is a completely different form of image making than darkroom photography. Digital cameras including cell phone cameras allow users to create, store and manipulate images composed of data recorded in pixels. Software tools such as Photoshop allow users to alter, combine and transform digital images well beyond the limits of traditional photography. Consumers began using digital cameras in the mid 1990s, and by 2002 they outnumbered the sales of analog cameras. In 2012 the widespread use of digital images led to the bankruptcy of Eastman Kodak.