Photograph Conservation Terminology
STRUCTURE AND CONDITION TERMS
Baryta: A mixture of barium sulfate in gelatin applied between a paper substrate and photographic binder or emulsion layer.
Binder or Emulsion: Any applied layer of material that contains the image-forming particles, typically albumen (egg white), collodion, gelatin, or gum arabic. (Note: some photographs do not include a binder or emulsion, such as salted-paper prints and platinum prints.)
Chemical stains: Discoloration or stains in the photographic image that are usually oxidation/reduction of the image-forming metal caused by residual processing chemicals.
Fiber-based paper: A primary support for photographic prints made of paper. The term is almost exclusively applied to gelatin silver prints to distinguish traditional paper supports from resin-coated paper supports.
Foxing: Small orange-brown stains in a paper that are the product of microorganisms or iron inclusions. These stains typically occur in large numbers scattered over an entire paper sheet or board.
Glass deterioration: Deterioration of glass caused by exposure to high humidity. It may appear as droplets or cloudiness on uncoated glass, or cause flaking of binders and emulsions.
Image: The information presented by a photograph separate from its physical being. Image loss or edge loss: An area where the binder or emulsion is missing but the substrate remains.
Media: The image forming material (typically silver, platinum, iron, pigment, dye) bound directly to the substrate or contained in a binder or emulsion. The media produces the image by scattering or absorbing incident light.
Photographic grade gelatin: A highly purified form of gelatin used for the emulsion on photographic film, paper, and plates.
Primary support: The substrate which holds the photographic media and binder or emulsion, if present. Is typically paper, glass, plastic film or metal.
Process: A specific combination of components (image material, binder or emulsion, support) such as gelatin silver developed-out paper (DOP) print, platinum print, or chromogenic color negative. Also, the specific method(s) employed to produce a photograph.
Resin-coated paper: A photographic print support of thin machine-made paper coated with polyethylene plastic on both sides. White titanium dioxide pigment is added to the polyethylene coating beneath the emulsion so that it functions as the baryta layer on fiber- based papers.
Retouching: Any artist media (graphite, watercolor, dyes) applied to a photograph at the time of its production to disguise a flaw or enhance an area of the image.
Secondary support: A substrate, most commonly paperboard and referred to as a ‘mount,’ that a photograph is adhered to for physical support and/or aesthetics purposes. Commercial mounts for photographs are often a standard size, such as the carte-de-visite.
Sheen: The overall appearance of the photographic surface: matte, glossy, semi-glossy, or ferrotyped (extreme gloss achieved by drying a photograph against a highly polished metal surface).
Silver mirroring: A metallic sheen in areas of high image density that is produced when silver ions from an oxidized image particle migrate to the surface of an emulsion.
Spotting: The retouching of small printed-in flaws.
Tertiary support: An additional substrate to which the secondary support is adhered.
Undulation or Cockling: An edge curl or overall waviness to a photographic print often caused by exposure to moisture.
Wove Paper: A handmade or machine-made paper with no laid or chain lines. When used as the primary support for photographs, this paper is typically made of cotton rag or highly purified wood pulp.
Aqueous surface cleaning: The removal of embedded dirt from the binder or emulsion using the local application of an aqueous solution, often deionized water with or without a surfactant or organic solvent.
Blotter washing: The washing of a photograph with water sensitive component(s) by placing it on a dampened paper or fabric support. This method removes soluble discoloration or deterioration products via capillary action through the verso.
Consolidation: The application of gelatin (or other appropriate adhesive) to secure loose or damaged photographic binder or emulsion.
Filling: The bridging of a loss in the support using a quality material with similar color, surface, and thickness to the surrounding area.
Humidification: The controlled and gentle introduction of moisture to relax a photograph with a paper support, and permit flattening.
Immersion Washing: The use of deionized water, occasionally in combination with solvents or surfactants, to bathe a photograph. The purpose of washing is to remove or reduce soluble deterioration products such as acidity or discoloration.
Inpainting: The application of artist media over an isolating layer to improve the visual aesthetics of the image, typically in an area of loss.
Isolating Layer: The application of a barrier of photographic grade gelatin or other appropriate material to separate inpainting media from the original object.
Light bleaching: The application of controlled light simultaneously with water to reduce stains and overall discoloration that cannot be achieved by washing in water alone. Both immersion and blotter washing techniques may be employed in this process.
Lining: The addition of an overall, reversible secondary support to the verso of a photograph.
Mending: The local joining of splits or tears in the support of a photograph using a non- yellowing, reversible adhesive. This may include the addition of paper to reinforce the area locally on the verso.
Photographic Activity Test (PAT): A test to determine if a storage/housing material will interact negatively with photographs. If a material has passed the PAT, it is safe to put it in direct or close contact with a photograph. Materials which have failed the PAT are likely to cause deterioration and should not be used.