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GLOSSARY
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A
absorption, absorb
The chemical action by which a liquid or gas is drawn into the permeable structure of a solid or fluid. This contrasts with adsorption, where the substances are simply held on the surface of the solid material. See also Adsorb, adsorption.
accept
To formally receive legal and physical custody of an item-usually a donation-for the purpose of including it in the collection. Donations and purchases should be documented by an exchange of appropriate paperwork.
accession
The process of registering and cataloguing an item into the collection.
accession number
The number which is assigned to each individual item during accessioning.
acclimatise
To adjust to a new climate or environment. See also Conditioned, conditioning.
accretions
Solid pieces of foreign matter attached to the surface of an object.
acid
A compound that produces hydrogen ions (H+) in aqueous solution. The concentration of hydrogen ions in water is known as acidity. See also Acidity.
acid-free
This term is used widely and has a number of definitions:
a) Acid-free can mean free of acids and free of materials that will break down to produce acids.
b) It can also mean free of acids and free of materials that will break down to produce acids, and containing alkaline buffers to neutralise acids.
Both these definitions would be acceptable to most conservators. Some manufacturers use acid-free to mean free of acids at the time of manufacture. In this case, there is no guarantee that the materials are of good quality.
When asking for acid-free materials, try to find out more about the manufacturer's specification. To minimise risk, buy from a reputable supplier of conservation materials.
acid-free PVA
A polyvinyl acetate adhesive specially formulated so that it does not give off acids. See also PVA.
acid gases, acidic gases
Gases, for example, sulphur dioxide, which may combine with atmospheric moisture to produce acids.
acid migration
The transfer of acid from an acidic material to one containing less or no acid. Also called acid transfer.
acid rain
Atmospheric precipitation with a pH below 5.7. Acid rain is caused by oxides of nitrogen and sulphur released into the air through the burning of fossil fuels for human heat and power. These oxides are converted into nitric and sulphuric acids and washed down in the rain. Acid rain can be particularly damaging to stone buildings, outdoor metal and stone sculpture.
acidity
A measure of how acid a solution may be. A solution with a pH of less than 7.0 is considered acidic.
acidic paper
Depending on the process used in its production, and the materials it is in contact with, paper can be acidic, neutral or alkaline. Many new papers are acidic and although they may initially be quite strong they will rapidly lose strength if they contain strong acids. This is due to chemical reactions that break down the chain length of the cellulose, the main component of paper. When paper loses most of its strength, it is said to be brittle.
acquisition
a) The process of obtaining legal possession-by purchase, donation or bequest-of an item for accessioning into the collection.
b) An object which has been donated, purchased or bequeathed and accepted into the collection.
acquisition committee
The body responsible for ensuring that the acquisition policy is followed.
acrylic
A group of plastics noted for their clear optical properties and durability. Acrylics have good resistance to the effects of sunlight and exposure to the elements over a long period of time. They do not yellow significantly or undergo significant changes in their physical properties. Acrylic sheets are used extensively for glazing in picture frames. Perspex and Plexiglas are trade names of manufactured acrylic sheeting. Acrylic resins are also widely used in binders for adhesives, paints and varnishes.
aerosols
A suspension of small liquid or solid particles in gas. See also Particulate matter.
adhesive
A substance capable of bonding materials to each other by chemical or mechanical action, or both, and which may be activated by water, non-aqueous solvents, pressure, heat, cold or other means. A desirable characteristic of adhesives used in conservation is reversibility.
adsorption, adsorb
The accumulation of molecules of a gas or liquid on the surface of another substance. Note that the accumulating molecules do not actually penetrate the substance they're on.
air-ride truck
A furniture removal style of truck in which the suspension has been specially designed to absorb most of the vibration and shock during motion. Also used to transport delicate scientific and computer instruments.
albumen
A class of soluble proteins in plants and animals. Albumen is found in egg white, milk and blood; and was used in early photography as an emulsion for photographs, glass slides and glass negatives. The albumen used for albumen prints came from egg whites. Albumen is also an ingredient in glair-a mixture of egg white and vinegar-an adhesive used by bookbinders for gilding and gold tooling. See also Glair.
alkali
A substance capable of forming hydroxyl ions (OH-) when dissolved in water. An aqueous alkaline solution is one with a pH value greater than 7.0. Alkalis neutralise acids producing a salt and water.
alkaline buffering
The addition of alkaline substances to neutralise acids that may be present in materials as a result of manufacture or the environment. Many chemicals can be used as alkaline buffers but the most common are magnesium or calcium carbonate. While alkaline buffering is useful to arrest paper deterioration, it can sometimes be damaging when placed in contact with other materials like leather or some types of photographs. See also Non-buffered.
allergen
A substance, usually a protein, which, when introduced into the body, makes it sensitive to that substance.
alloy
A material composed of two or more metals which are mixed and united-usually when they are in a molten state. Alloys are created to improve properties such as the appearance, strength and durability of metals. Common alloys include cast iron, stainless steel, brass, bronze and sterling silver.
alpha cellulose
That part of a material made of cellulose that is insoluble in a 17.5% solution of sodium hydroxide at 20¡C under specified conditions. While alpha cellulose consists principally of cellulose, it does include other components that are insoluble under the test conditions. Because the permanence of paper depends to some extent on the absence of non-cellulosic impurities, the determination of true cellulose-alpha cellulose-gives an indication of the stability of the paper and therefore its permanence. The term alpha cellulose in a paper or board specification generally indicates a high-quality product.
alum rosin sizing
Used in the papermaking process to size paper. Because rosin does not attach readily to paper, papermaker's alum-aluminium sulphate-is used to form a link between the paper and the rosin. Alum rosin sizing has been used in most machine-made papers from the 19th century to the present, and is a primary source of acid in paper causing it to become brittle. See also Sizing, Sizes.
alum tawed leather
Skin treated with alum rather than tanning agents. Tawing does not actually produce a skin that is stable in the wet condition, and therefore cannot accurately be described as having been tanned; consequently, in a strict sense, a tawed skin is not leather. Alum tawed skin can be recognised by its bulk and accentuated hair follicles.
ambrotype
A photographic process which produces a wet collodion negative image on glass, which is backed with black paper or lacquer to give a positive image. The ambrotype was a popular portrait medium in the 1850s. See also Tintype.
AMOL
See Australian Museums On Line.
analogue, analog
Refers to continuous variation of a magnitude in computation. For example, an analogue watch models the passage of time with hands which move smoothly around its face. Information in analogue format implies continuous flow without abrupt steps. Any information we want to understand has to already be in analogue format or converted to analogue format before we can use it.
In contrast, digital means by numbers. So a digital watch displays the current time as a set of numbers which change abruptly at regular intervals, whereas in an analogue watch the motion is continuous. See also Digital.
aniline dye
A class of synthetic, organic dyes originally obtained from aniline-coal tars-which were, in fact, the first synthetic dyes. Today the term is used with reference to any synthetic organic dyes and pigments, regardless of source, in contrast to animal or vegetable colouring materials, natural earth pigments, and synthetic inorganic pigments. Aniline dyes are classified according to their degree of brightness or their light fastness. Basic dyes are known for their extreme brightness, as well as for their lack of colour fastness. See also dye.
archival-quality material
An imprecise term suggesting that a material, product or process is durable, and/or chemically stable, that it has a long life and can therefore be used for conservation purposes. The phrase is not quantifiable; no standards exist that describe how long an 'archival' material will last. The word permanent is sometimes used to mean the same thing.
Archival-quality material can be used safely for long-term display or storage of photographs, maps and historic records without causing deterioration. These materials usually contain additives that will slow down deterioration caused by other factors. Archival-quality papers, cards and boards are made from high quality cellulose fibres such as those from rags. Archival quality plastics are inert and adhesives are stable without acids. See also Acid-free; Conservation grade; Museum quality; Photographic quality.
armature
A framework or support upon which a sculptor builds a work in clay, plaster or plastic substances. Also used to refer to an internal support in a finished work, or an internal support provided as part of a conservation treatment.
Australian Institute for the Conservation of Cultural Material (AICCM)
AICCM was established in 1973 as the national organisation for conservators and people interested in the preservation of the nation's heritage. AICCM is governed by a National Council and each State has a local division. AICCM produces a Bulletin of current conservation techniques, a quarterly national newsletter and some State divisional newsletters. Professional accreditation by peer review process is available to members.
Australian Museums On Line (AMOL)
An Internet site established by the Museums On Line Heritage Collections Council which contains a directory of Australian museums, searchable collections, and substantial resources on conservation issues. The site may be found on http://amol.org.au
auxiliary support
In picture framing, the structure to which the support is attached. In a traditional painting this is usually a wooden stretcher. See also Support; Strainer; Stretcher.
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