The conservation and restoration of photographs is the study of the physical care and treatment of photographic materials. It covers both efforts undertaken by photograph conservators, librarians, archivists, and museum curators who manage photograph collections at a variety of cultural heritage institutions, as well as steps taken to preserve collections of personal and family photographs. It is an umbrella term that includes both preventative preservation activities such as environmental control and conservation techniques that involve treating individual items. Both preservation and conservation require an in-depth understanding of how photographs are made, and the causes and prevention of deterioration. Conservator-restorers use this knowledge to treat photographic materials, stabilizing them from further deterioration, and sometimes restoring them for aesthetic purposes.
While conservation can improve the appearance of a photograph, image quality is not the primary purpose of conservation. Conservators will try to improve the visual appearance of a photograph as much as possible, while also ensuring its long-term survival and adhering the profession's ethical standards. Photograph conservators also play a role in the field of connoisseurship. Their understanding of the physical object and its structure makes them uniquely suited to a technical examination of the photograph, which can reveal clues about how, when, and where it was made.
Photograph preservation is distinguished from digital or optical restoration, which is concerned with creating and editing a digital copy of the original image rather than treating the original photographic material. Photograph preservation does not normally include moving image materials, which by their nature require a very different approach. Film preservation concerns itself with these materials.
Photographic processes Physical photographs usually consist of three components: the final image material (e.g. silver, platinum, dyes, or pigments), the transparent binder layer (e.g. albumen, collodion, or gelatin) in which the final image material is suspended, and the primary support (e.g. paper, glass, metal, or plastic). These components affect the susceptibility of photos to damage and the preservation and conservation methods required.American Institute for Conservation of Historic and Artistic Works (AIC), Caring for Your Treasures, accessed August 12, 2011, http://www.conservation-us.org/_data/n_0001/resources/live/photographs.pdf. Photograph preservation and conservation are also concerned with the negatives from which most old photographic prints are made. Most negatives are either glass plate or film-based.
Timeline
Source:Unless otherwise noted, material in this section comes from the following sources: Joanna Norman, "Photographic Collections Management", Journal of Educational Media and Library Sciences 39, no. 4 (2002): 365-69; Bruce Warren, Photography (Minneapolis/St. Paul: West Pub. Co., 1993); 임양환, (검프린트에서 디지털 네거티브까지)특수사진 인화기법 (서울: 타임스페이스, 2005).
1816: HeliographyThe first person who succeeded in producing a paper negative of the camera image was Joseph Nicephore Niepce. He coated pewter plates with bitumen (an asphaltic varnish that hardens with exposure to light) and put them in a Camera Obscura. After exposure to sunlight for a long time, the parts that were exposed to light became hard and the parts that were not could be washed off with lavender oil.
1837: DaguerreotypeThe daguerreotype process (named after Louis Jacques Mande Daguerre) produces a unique image, as there is no negative created. After coating a copper plate with light-sensitive silver iodide, the plate is exposed to an image for over 20 minutes and then treated with fumes from heated mercury. The longer the exposure to light, the more mercury fumes are adsorbed by the silver iodide. After the plate is washed with salt water, the image appears, reversed. This was the earliest photographic process to gain popularity in America.Debbie Hess Norris, "The Proper Storage and Display of a Photographic Collection", The Book and Paper Annual 2 (1983), accessed August 12, 2011, http://cool.conservation-us.org/coolaic/sg/bpg/annual/v02/bp02-08.html. It was used until around 1860.Gary Albright and Monique Fischer, Types of Photographs, Preservation Leaflets (Northeast Document Conservation Center), accessed August 12, 2011, http://www.nedcc.org/resources/leaflets/5Photographs/02TypesOfPhotos.php .
1839: Salt printThis was the dominant form of paper print until Albumen prints were introduced in 1850. Salt prints were made using both paper and glass negatives.
1841: CalotypeWilliam Henry Fox Talbot invented the negative-positive system of photography commonly used today. He first developed the Talbotype, which used silver chloride to sensitize paper. After improving the process by using silver iodide, he renamed it Calotype. The process could produce many positive images, but they were not as sharp because they were printed on fibrous paper rather than glass.
1842: Cyanotype (Ferro-plusiate, Blue process)This process forms blue-colored images through a reaction to iron salts. John Herschel studied it in order to reproduce his complicated math formulas and memos. Other processes that fall into this category include Kallitype, Vandyketype, and Platinum printing.
1850: Albumen printThis process, introduced by Louis Désiré Blanquart-Evrard, was the most common kind of print in the latter half of the nineteenth century. Beautiful sepia gradation images were created by using albumen and silver chloride. The surfaces of prints made with this process were glossy because of the egg whites which were layered heavily to prevent the originally thin prints from curling, cracking, or tearing easily. This type of print was especially common for studio portraits and landscape or stereoviews.
1851: Wet collodion process and AmbrotypeFrederick Scott Archer developed the wet collodion processes, which used a thick glass plate unevenly hand-coated with a collodion-based, light-sensitive emulsion. Collodion, which means ‘glue’ in Greek, is nitrocellulose dissolved in ether and ethanol. The Ambrotype, an adaptation of the wet collodion process, was developed by Archer and Peter W. Fry. It involved placing a dark background behind the glass so that the negative image would look positive, and was popular in America until around 1870.
1855: Gum printing Orange colored dichromate has photosensitivity when it is mixed with colloids such as gum arabic, albumen, or gelatin. Using that feature, Alphonse Poitevin invented the gum printing process. It gained in popularity after 1898, and again in 1960s and 1970s because of its unique look.
1858: Tintype (also called Ferrotype and Melainotype) In this photographic process the emulsion was painted directly onto a japanned (varnish finish) iron plate. it was much cheaper and sturdier than the Ambrotype and Daguerreotype.
1861: RGB additive color modelApplied physician James Clerk Maxwell made the first color photo by mixing red, green, and blue light.
1871: Gelatin dry plateRichard L. Maddox discovered that gelatin could be a carrier for silver salts. By 1879, the gelatin dry plate had replaced the collodion wet plate. It was a revolutionary innovation in photography since it needed less light exposure, was usable when dry, meaning photographers no longer needed to pack and carry dangerous liquids, and could be standardized because it could be factory produced.
1873: Platinum printing (Platinotype)William Willis patented platinum printing in Britain. The process rapidly spread and became a dominant method in Europe and America by 1894 since it had a visibly different color tone compared to albumen and gelatin silver prints.
Late 1880s: Gelatin silver printThis has been the major photograph printing process since the late 1880s up to the present. Prints consist of paper coated with an emulsion of silver halide in gelatin. The surface is generally smooth; under magnification, the print appears to sparkle.Diane DeCesare Ross, "An Overview of the Care of Silver-Based Photographic Prints and Negatives," Mississippi Libraries 65, no. 2 (Summer 2001): 42.
1889: KallitypeDr. W. W. J. Nicol invented and refined the Kallitype. Vandyketype, or Single Kalliitype, is the simplest type of Kalltype and creates beautiful brown images.
1889: Film negativesCellulose nitrate film was developed by Eastman Kodak in 1889 and refined in 1903. It is made of silver gelatin on a cellulose nitrate base. The negatives are flammable and therefore can be dangerous. Nitrate sheet film was used widely though the 1930s, while nitrate roll film was used through the 1950s. The nitrate base was replaced with cellulose acetate in 1923. By 1937, Cellulose diacetate was used as the base, and beginning in 1947 Cellulose triacetate was used.Paul Messier, "Preserving Your Collection of Film-Based Negatives" (Rocky Mountain Conservation Center, 1993), accessed August 12, 2011, http://cool.conservation-us.org/byauth/messier/negrmcc.html. Polyester film was introduced around 1960.International Federation of Library Associations and Institutions (IFLA) Core Programme Preservation and Conservation, Care, Handling and Storage of Photographs: Information Leaflet, (1992, revised and updated 2002), accessed August 12, 2011, https://www.loc.gov/preservation/resources/care/photolea.html.
1935: Color photographsKodak introduced color film and transparencies in 1935. The first process was called Kodachrome.Henry Wilhelm, "Monitoring the Fading and Staining of Color Photographic Prints," Journal of the American Institute for Conservation 21, no. 1 (1981), accessed August 12, 2011, http://cool.conservation-us.org/jaic/articles/jaic21-01-003.html. Ektachrome, introduced in the late 1940s, became equally popular. There are now a variety of color processes that use different materials; most consist of dyes (cyan, magenta, and yellow, each of which have different absorption peaks) suspended in a gelatin layer.Mary Fahey, The Care and Preservation of Photographic Prints (Dearborn, MI: The Henry Ford), accessed August 12, 2011, http://www.thehenryford.org/research/caring/prints.aspx .
Photograph stability Photograph stability refers to the ability of prints and film to remain visibly unchanged over periods of time. Different photographic processes yield varying degrees of stability. In addition, different materials may have dark-storage stability which differs from their stability in light.
Kodachrome An extreme case with slides was stability under the intense light of projection. When stored in darkness, Kodachrome's long-term stability under suitable conditions is superior to other types of color film. Images on Kodachrome slides over fifty years old retain accurate color and density. Kodachrome film stored in darkness is largely responsible for excellent color footage of World War II, for example. It has been calculated that the yellow dye in Kodachrome, the least stable, would suffer a 20% loss of dye in 185 years. This is because developed Kodachrome does not retain unused color couplers. However, Kodachrome's color stability under bright light, especially during projection, is inferior to substantive slide films. Kodachrome's fade time under projection is about one hour, compared to Fujichrome's two and a half hours. Thus, old Kodachrome slides should be exposed to light only when copying to another medium.