Unlike conventional works of art, photographs are created by the actions of light and chemicals. For more than 160 years, countless photographs have been made by a variety of complex processes, many of which have faded away due to their inherent instability or overexposure to high levels of light, heat, humidity, and/or pollution. Photograph conservators work with scientists and historians to understand how these delicate works were made and why some images have changed over time, as well as to design procedures to stabilize photographs and improve their appearance. Conservators and scientists also work closely with exhibition designers to ensure that the images are protected from the damage that can be caused by display.
Photographs can be made with many different materials. The black image in a black-and-white photograph can consist of any number of substances, such as microscopic amounts of silver, platinum, pigment, or dye. This image material may reside directly on a paper support or it may rest in a transparent layer, such as gelatin, coated onto paper, glass, plastic film, or metal. Photographs can even be made on wood, leather, or textiles; as part of a multimedia work. They may also have cases, mounts, or frames that are integral to the work. Color photographs are made by extremely complex processes, which makes their care especially complicated and challenging for conservators.
Photograph conservators are called upon to explain why the images look the way they do, provide advice to prevent changes and to repair damage. These tasks require in-depth technical understanding of photographic materials and the causes and manners of physical and chemical change, as well as the skills to perform successful treatments. Conservation treatments might include flattening prints, removing tape, or mending tears. More challenging problems might require careful testing and scientific investigations to achieve lasting improvement of a photograph. The advice we give most often to preserve photographs for future generations is to handle them with care, house them in high-quality enclosures, store them in a cool, dry, dark environment, and display them in subdued light.