Today, digital photography has become the predominant way people produce and consume images. But not long ago, photography was a fully analog process, requiring light-sensitive film and paper, wet chemistry and complex darkroom equipment. While digital photographs offer many advantages in terms of speed, adaptability and cost, there is a sense in which something indefinable is lost in a crisp, perfectly rendered digital print—just as a digital music file fails, for some sensitive ears, to capture the richness of analog sound.
The photographs shown here began as digital captures, which have been converted to negatives and printed on an ink-jet printer. But all of the final prints were made using a variety of historic or “alternative” processes that were originally developed in the 19th century. These processes were chosen because of their unique contribution to the visual quality of the print, including its surface texture, tonal range and color space. Because they have such a strong effect on the photograph’s final appearance they are a vital part of the work, as are the subjects of the pictures.
The black-and-white images are salted paper prints which have been toned with a gold solution. Developed in the 1830’s by William Henry Fox Talbot, salt prints were the dominant photographic printing process of the mid-19th century. In this process, a sheet of Bristol paper is coated with a layer of gelatin and salt (sodium or ammonium chloride), and then a thin coating of silver nitrate, which renders it light-sensitive. The sensitized sheet is then placed in contact with a negative and exposed to bright light for up to 30 minutes, forming a visible image. After a brief wash in salt water, it is toned with auric (gold) chloride, which gives the finished print a somewhat cooler tone with deep, rich blacks. Finally, the print is treated with “fixer” (sodium thiosulfate) to remove the unexposed silver compounds and prevent the image from fading; it is then washed in water for archival permanence.
The cyanotype process, invented by British scientist John Herschel in the 1840’s, takes advantage of the light-sensitive properties of iron salts to produce a “blueprint” image with exposure to strong UV light. It was used by pioneering photographers Anna Atkins and others, and is still used by contemporary artists today. Cyanotypes can be printed on different surfaces, including paper and glass, and can be toned to produce a range of colors.
The multi-color images are made using multiple layers of gum bichromate over cyanotype, printed on heavy (300 g/m2) watercolor paper sized with gelatin. The gum process was perfected in the 1850’s with contributions from a number of experimenters, notably Scottish inventor Mungo Ponton and French chemist Alphonse Louis Poitevin. The process reached its zenith around the turn of the 20th century, when it was embraced by pictorialist photographers including Edward Steichen and Robert Demachy.
In the first step of the process, artist paper is coated with a colloidal layer of gum arabic, tinted with watercolor paint and sensitized with chromium salts (ammonium or potassium dichromate). It is then placed in contact with a negative and exposed to bright UV light. This causes the parts of the image where light reaches the gelatin to be hardened, while the other areas remain soft. After exposure the soft areas are washed away, revealing fine details in the picture. Several layers of different colors can be built up, one over another, to produce a full-color image. This enables the gummist to control the process at every step, choosing hue and intensity as well as manipulating the surface of the print.