Photograph Conservation Terminology

A glossary of photograph conservation terminology.

Structure and condition terms:

Primary support: The photographic image, binder, and substrate (see definition below).

Secondary support: A 19th-century paperboard mount found on cabinet cards, carte-de-visites, or other photographic objects, to which the photograph is mounted overall or at each of the four corners with an adhesive. In 20th-century photography, this term can be applied to any window mats, paperboards, or mounts used to support a photograph by means of hinging, overall adhesion, or dry mounting.

Tertiary support: A paperboard that has a mounted photograph attached to it. An example of this would be a cabinet card hinged to a window mat.

Process: A term used to describe a specific photograph method used to produce the image, such as silver gelatin developed-out paper (DOP) print, albumen print, platinum print, etc.

Media: The image material (silver, platinum, iron, pigment) contained in the binder, if applicable. (Note: some photographic processes do not contain a binder, such as salted-paper prints and platinum prints.)

Emulsion or Binder: Any applied layer of material that contains the image-forming photographic metal, typically albumen (egg binder), collodion, gelatin, or gum arabic.

Substrate: Used to describe the particular support that holds the photographic image, typically metal, glass, paper, or

Baryta: A layer of barium sulfate applied between the paper substrate and the photographic image that provides an opaque layer of material that allows for a glossy photographic image.

Photographic-grade gelatin: A highly purified form of gelatin used in the production of photographic paper and film that is non-yellowing.

Wove photographic paper: A handmade or machine-made paper with no laid or chain lines, typically made of 100% cotton rag or highly purified wood pulp paper with added stabilizers.

Sheen: The overall appearance of the photographic surface: matte, glossy, semi-glossy, or ferrotyped (extreme gloss achieved by a heated drum or metal plate).

Historic retouching: Any artist media (graphite, watercolor, Spot-Tone) that was applied to a photographic print at the time of its production to disguise a flaw or enhance an area of the photographic image.

Surface grime: Dirt, dust, and other accumulations that sit on the surface of the photographic image or within the binder of the photographic image. 

Image loss or edge loss: An area where the emulsion is missing but the substrate still remains.

Emulsion cracks: Fine cracks that form in the emulsion/binder that cause a disruption in the image surface or a partial lifting (delamination) of the emulsion from the support.

Chemical stains: Damages or stains in the photographic image, usually caused by poor chemical processing or oxidation/reduction of the image forming metal.

Undulation: An edge curl or overall waviness to a photographic paper caused by exposure to moisture.

Isolating layer: A barrier layer of photographic-grade gelatin or other appropriate material that separates any inpainting media from the original photograph.

Treatment terms:

Aqueous surface cleaning: The removal of embedded dirt within the emulsion using an aqueous solution (deionized water with or without a surfactant) applied by swabs.

Consolidation: The brush application of gelatin (or other appropriate consolidant) used to secure loose, damaged, or missing photographic emulsion.

Immersion washing: To use deionized water, occasionally in combination with other solvents or surfactants, to bathe a photographic print. The purpose of washing is to remove or reduce soluble deterioration products such as acidity or discoloration from the paper support and emulsion.

Blotter washing: To wash a photographic image with sensitive media on the recto using a dampened paper or fabric support. This removes soluble deterioration products via capillary action through the verso only.

Light bleaching: The simultaneous use of controlled light and water to reduce stains and overall yellowing that cannot be achieved by washing in water alone. Both immersion and blotter washing techniques can be employed in this process.

Mending: To locally join splits or tears in the paper support of a photograph using a non-yellowing, reversible adhesive.

Lining: To provide an overall, reversible secondary support to the verso of a photograph.

Humidification: The controlled and gentle introduction of moisture within a contained environment that allows the photographic emulsion and paper support to simultaneously relax in order to be flattened overall.

Inpainting: The application of an artist media over an isolating layer that improves the visual aesthetics of the image.

Photographic Activity Test (PAT): An independent test done to determine if a storage/housing material will interact negatively with the image-forming material of a photograph. If a material has passed the PAT, it is safe to put it in direct contact with a photograph. Materials that have not passed the PAT will cause deterioration of the photographic silver and should not be used when housing/storing photographic material.