Historical Processes: Carbon and Carbro Prints

The years between the mid-19th and mid-20th centuries were some of the most inventive for photographic processes. As the camera began to be taken seriously as an expressive tool, photographers started exploring the creative possibilities offered by various printing processes, including pigment-based printing techniques such as carbon printing and later carbro printing.

Above photograph: Harry Warnecke, Inauguration of Franklin Delano Roosevelt, 1937, 1937, carbro print. Courtesy of the National Portrait Gallery, Smithsonian Institution

The earliest experiments into pigment printing using carbon trace back to the French chemist Alphonse-Louise Poitevin, who, in 1859, patented a method of creating photographs using a carbon, potassium dichromate, and gelatin emulsion. Although his experiments set important precedents for a range of future photographic processes, Poitevin’s images were contrasty, because the process lacked the ability to render fine detail. Five years later, British scientist and inventor Joseph Swan refined Poitevin’s process and patented a tissue-based carbon printing method with a more complete tonal range.

While the carbon printing process derives its name from the carbon black used in its earliest form, Swan also created sepia and purple-brown offshoots, foreshadowing the wide range of colors that would later become available. In 1868, Swan sold his patent to John Robert Johnson and Ernest Edwards, who, together, formed the Autotype Printing and Publishing Company. Although embraced by a handful of early apostles of art photography, carbon printing was initially celebrated as a novel means of reproducing artworks and illustrating books. As commercial interest grew, dozens of colors became available for creative applications.

In brief, the carbon print process begins by coating a backing paper with gelatin mixed with pigment to produce a “carbon tissue.” This medium is sensitized to light using a solution of potassium dichromate and allowed to dry in the dark. Once dry, the carbon tissue is exposed by contact printing with a negative on top. The gelatin hardens in areas exposed to the light. After exposure, the paper is soaked in cold water along with a second sheet of paper. Both sheets are removed from the water and pressed together like a sandwich before being soaked in warm water. The original backing paper is carefully peeled away, and unexposed gelatin washes to reveal an image in relief on the new receiving paper. The resulting image is laterally reversed and must be transferred a second time to correct for this inversion. Though produced through a laborious process, carbon prints are among the most archivally stable photographic prints that can be created.

It was only a matter of time before photographers latched onto the unique aesthetic and textured emulsions of the carbon print. Among early adopters was British photographer Julia Margaret Cameron, whose penchant for soft lenses meshed well with the sketch-like prints made possible by the technique. Still, carbon printing was not widely adopted by photographers until decades later when Alfred Stieglitz advocated its use to fellow Pictorialists, who were eager to explore less conventional approaches to image making. From the late 19th century onward, carbon printing became an attractive medium for photographers looking to create permanent prints in a variety of tones.

In 1905, Thomas Manly presented a variation on the carbon printing process capable of producing color images: carbro (CARbon + BROmide) printing, which involves pairing pigmented sheets of dichromated gelatin with filtered bromide prints.

A subtractive color process, carbro printing requires three separation negatives to be made using color filters. Each negative is used to make a bromide print, which is then squeezed together with its corresponding pigmented carbon tissue: cyan, magenta, or yellow. The carbon tissue reacts to the silver in the bromide print, causing the gelatin to harden in proportion to the silver density across the image. The carbon tissues are removed from the print and washed to get rid of any unreacted gelatin before being carefully aligned on a support medium to form a single image. When inspecting an uncropped carbro print, you will notice the layered color tissues at the edge of the image.

An especially labor-intensive process, carbro printing, like carbon printing, results in extremely stable photographs over time. The technique was adopted by artists ranging from Nickolas Murray to Man Ray in the early 20th century. Beyond the art world, carbro printing was used by documentary and portrait photographers eager to create color images. The process would be phased out by midcentury on account of the rise of the more user-friendly dye imbibition printing process for making color photographs.

Have you experimented with carbon or carbro printing? Have you seen prints made using this process in person? Share your thoughts in the Comments section, below. And don’t forget to check out Explora’s Classic Cameras Series, where you can learn about more historical processes as well as the stories behind some of our favorite cameras!