ANSI – Abbreviation for the American National Standards Institute.

Acid-free – Materials that have a pH of 7.0 or higher.  Sometimes used incorrectly as a synonym for alkaline or buffered. Such materials may be produced or buffered.  They may be produced from virtually any cellulose fiber source (cotton and wood, among others), if proper measures are taken during manufacturing. Active acid from bleaching, aluminum sulfate from sizing, or pollutants in the atmosphere may lead to the formation of acid unless the paper or board has been buffered with an alkaline substance.

Archival – A non-technical term that suggests that a material or product is permanent, durable, or chemically-stable, and that it can therefore be safely used for preservation purposes.  The phrase is not quantifiable: no standards exist that describe how long an “archival” or “Archivally-Sound” material will last.

Buffering – The addition of alkaline agents such as calcium or magnesium carbonate during the papermaking process in order to counteract the effect of acidic contamination.  The degree of buffering (usually 2-3%) is measured by percentage of paper weight.  See alkaline.

Calcium Carbonate – An alkaline chemical used as a buffer in papers and boards. 

Chromogenic dyes – Dyes or color produced in a color print by a colorless dye pre-cursor embedded in the photographic emulsion combined with a dye coupler I, the developer solution. The interaction of the two after the exposure to light produces a color print. Prints are produced from color negatives. 

Conservation – A term used to describe a physical or chemical treatment of an original image to restore its original condition and appearance.

CRI rating – Abbreviation for Color Rendering Index.  Represents a numerical rating (95 being the standard) for overall brightness and evenness of a viewing light field, as in a light table.

De-Acidification – A common term for a chemical treatment that neutralizes acid in a material such as paper and deposits an alkaline buffer to counteract future acid attack.  While de-acidification increases the chemical stability of paper, it does not restore strength or flexibility to brittle materials. See also pH.

Desiccant – Any agent, particularly a silica gel, that removes gaseous water from the air and reduces relative humidity.  Desiccants can be used in sealed enclosures to protect photographs from humidity. Since silica gels can be made to give up their absorbed moisture by heating, desiccants may be reused. 

Emulsion – The light-sensitive coating on photographic film or printing paper.

Lignin – An acid organic substance found in wood pulp. It is removed in the chemical pulping process, but it is not removed in the manufacture of low-grade papers made of ground wood pulp, such as newsprint. 

Non-buffered – As in non-buffered paper, pulp which is not impregnated with buffering agents such as calcium carbonate.  Some buffering agents have adverse effects on various types of photographic prints.

PAT (Photographic Activity Test) – Accelerated aging test using a specialized photo-emulsion in contact with a paper sample at elevated temperature and humidity levels to simulate the natural aging process. It is used to check the archival quality of various papers and paper products.

pH Neutral – Exhibiting neither acid nor alkaline qualities. 7.0 on the pH scale.

Polypropylene (extruded and case) – A chemically stable, highly flexible, transparent, or translucent plastic with a low melting point.  Used in preservation to make sleeves for photographic materials, when made with no surface coatings or additives.

Preservation – Action taken to retard or prevent deterioration or damage.
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