Archival Glossary

Archival Glossary

A.N.S.I - Abbreviation for American National Standards Institute.

accelerated ailing tests - A process using elevated temperature and humidity to simulate the natural aging process on material samples.

acetates - Material composed of cellulose combined with acetic and sulfuric acids used in making various products including photographic films and packaging sheets. Tri-acetates are archival; di- acetates are not.

acid - In chemistry, a substance capable of forming hydrogen ions when dissolved in water. Acids can weaken cellulose in paper, board, and cloth, leading to embrittlement. Acids may be introduced in the manufacture of papers and may be left in intentionally (as in certain sizings) or incidentally (insufficient bleaching). Acids may also be introduced by migration from other materials or from atmospheric pollution. See also pH and acid migration.

acid migration - The transfer of acid from an acidic material to a less acidic or pH neutral material. This may occur directly, when the two materials are in intimate contact. For instance, acid may migrate from boards, endpapers, and protective tissues, as well as the paper covers of books and pamphlets, to the less acidic paper of the text.

acid-free paper - In principle, papers which contain no free acid and have a pH value of 7.0 or greater. Such papers may be produced from cotton fibers or chemical wood pulps, or virtually any other fiber. However free of acid the paper may be after manufacture the paper must also not have aluminum sulfate (alum) sizing applied to the surface. Unless the paper has been buffered with a substance capable of neutralizing acids, (calcium carbonate) overtime pollution in the atmosphere will make the paper acidic. The term “Acid Free” does not necessarily mean the paper is safe to use in archival applications. Look for additional specification on what the paper is made of, cotton or purified wood pulp, buffering content and neutral or alkaline sizing is used.

acid-neutralizing paper - A type of paper which contains an alkaline neutralizer intended to absorb any acidity that may appear in the environment of a book or work of art on paper.

acrylic - A plastic noted for transparency, light weight, weather resistance, color fastness and rigidity. In addition to these qualities, acrylics are important in preservation because of their stability, or resistance to chemical change over time, a characteristic not common to all plastics. acrylics are available in sheets, films, and resin adhesives. Some common trade names for the sheet form are: Perspex, Lucite and Plexi-Glass.

acrylic impregnated buckram - A heavy gauge covering cloth used- in book binding and presentation cases. Acrylic fillers are added to the buckram cloth to inhibit moisture and dirt from attacking the binding, providing a cleaner and longer lasting case. Typically used on public library and text books, and on portfolio box and binders.

actinic - (as in actinic light) Light radiation in the visible and UV spectrum that causes chemical changes and reactions, especially to photographic emulsions.

adhesive - A substance capable of holding materials together by surface attachment. It includes such materials as glue, mucilage, and paste. Archival adhesives have a neutral pH and are sulfur- free.

albumen prints - An antiquarian photographic printing process most popular from the 1850s to the 1890s utilizing the whites of eggs (albumen) instead of gelatin--in current use--to form the emulsion.

alkali - A caustic substance having a pH above 7. It has the quality of neutralizing acid.

alkaline - Alkaline substances have a pH over 7.0. They may be added to a material to neutralize acids or as an alkaline reserve or buffer for the purpose of counteracting acids that may form in the future. A buffer may be added during manufacture or during the process of deacidification. While a number of chemicals may be used as buffers, the most common are magnesium carbonate and calcium carbonate.

alkaline reserve - Buffer or reserve of an alkaline substance added to paper to counteract acid. Usually 3 percent precipitated calcium or magnesium carbonate by weight of paper.

alpha cellulose - A form of cellulose derived from cotton. The presence of high percentages (87%+) of alpha cellulose in paper or board is one indication of its stability or longevity. Non-cellulosic components of wood are believed to contribute to the degradation of paper and board.

alternative process - Typically, processes not involving popular black and white/gelatin silver emulsions available commercially, but rather processes that require the artist to mix and hand coat emulsions onto a support (paper, cloth, etc.) by hand. Examples include cyanotype, kallitype, VanDyke, and gum bichromate processes.

alum - Aluminum sulfate used with rosin to size paper, giving it water-resistant properties. Alum sized paper is acidic and therefore undesirable for archival applications.

anti-Newton Ring Glass - Specially coated glass designed to eliminate the optical phenomena of Newton Rings, a rainbow. ring effect caused by air pockets trapped between two layers of transparent materials, as in glass or mylar.

anti-tarnish adhesive - Adhesive whose properties will not adversely affect the surface of a metal, especially silver.

aperture - An opening, as in that of a photographic lens, which may be adjusted in measured pre-set diameters to control the amount of light in exposing light sensitive film. Used in tandem with a shutter and its various shutter speeds to control the effect of depth of field in recording an image (latent) on film.

archival processing - Photographic processing procedures designed to result in maximum permanence and stability of negatives and prints through a series of precise fixing, washing, and toning baths. Following thorough washing, photographs are treated with a gold solution or a toner, such as selenium. Archival processing requires the use of fiber-based rather than resin-coated papers. Archival processing alone will not insure archival quality; adherence to precise storage and handling procedures (as specified by the American National Standards Institute) is also required.

archival rinse - A washing agent used to assist in the maximum removal of residual fixer (hypo), silver sulfur compounds, and other harmful chemistry that would adversely effect image permanence on emulsions and paper board fibers. Also, shortens rinsing time and water consumption for some degree of permanence

archival; archivally sound - A non-technical term that suggests that a material or product is permanent, durable, or chemically stable, and that it can therefore safely be used for preservation purposes. the phrase is not quantifiable; no standards exist that describe how long an "archival" or “archivally sound" material will last.

archives - The non-current records of an organization or institution preserved because of the continuing value (see also collection). 2) The agency responsible for selecting, preserving, and making available archival materials.

atmospheric acid contaminations - Adverse contamination of object surfaces (as in photographic prints, drawings or paintings) caused by acidic particles and elements suspended in the immediate air environment or atmosphere.