Silver Gelatin
Silver gelatin photographs were developed in 1871 when English photographer and physician Richard Leach Maddox came up with the idea of replacing the toxic solutions used in the wet plate collodion process with a common candy making ingredient of the time: gelatin. By suspending the light-sensitive elements of the wet plate process in gelatin, Maddox had found a safer and easier process. In 1874, the first silver-gelatin print papers were produced and became popular with photographers of the time. However, it wasn’t until 1890 when commercially available developing-out printing paper was standardized that mass production began globally.
Process
By 1894, a breakthrough was discovered: The application of a thin coating of barium sulfate on print paper increased the smoothness and reflectiveness of the cotton paper underneath. This “baryta” layer proved key to the success of the silver gelatin process by creating a whiter and smoother surface to apply the light-sensitive silver halides suspended in a gelatin solution. When a negative was used to create an image in the silver halides, the image was fixed after exposure to create a rich photographic print with good durability and high image detail.
Portrait of Florence La Due in 1912. Florence was a vaudeville performer and wife of the Calgary Stampede founder, Guy Weadick. A photographer’s mark has been pressed into the corner of the photo. Glenbow Library and Archives, UCalgary: PA-829-52.
Silver Gelatin photograph of movie star Hoot Gibson in Alberta. Photos printed on thin paper as this one was, were generally intended to be mounted in a rigid folder. Glenbow Library and Archives, UCalgary: PA-829-14.
How it is used
This process is still very much in use today and continues to be refined within the photographic printing community.
Movie star Hoot Gibson (8th cowboy from left) and friends in Alberta. This thin-papered gelatin print is slightly yellowed but the image remains strong. Glenbow Library and Archives, UCalgary: PA-829-24.
Deterioration characteristics
Despite the overall durability of the process, silver-gelatin prints are susceptible to reactions with oxygen in the air which can result in the image becoming faded and yellowed over time. The paper backing is a food source for insect pests and improper storage can result in mould and brittleness. Changes in temperature and relative humidity can cause prints to curl or crack. Storing photos in the dark with consistent temperature and relative humidity will protect against these threats to their longevity.
Digging a water well on a northern Alberta farmstead. This photo shows cracking of the emulsion and paper support typical of deteriorated silver gelatin emulsion photographs. Glenbow Library and Archives, UCalgary: PA-893-43.