Paper has various properties that contribute to its performance, the most notable of which are pH level, strength, opacity and whiteness.
Acidity and alkalinity are measured on a scale known as the pH scale. Papers with a high level of acidity tend to deteriorate quickly. This is because the acids in the paper attack the cellulose fibres and weaken their structure. This type of deterioration causes paper to become very brittle and discoloured.
Certain ingredients in paper can also cause acid to form as the paper ages; chief among these is lignin, a common impurity in paper made from wood pulp. Acidity from external sources such as air pollution and finger grease can also affect paper. For a paper to be considered truly permanent, it must have a level of alkaline material added during its manufacture to neutralise all these acids as they appear.
The physical strength of a paper can also affect its longevity. A paper needs physical strength to ensure it can withstand repeated handling and the stresses of photocopying, particularly photocopying utilising an automatic feeder. Paper strength is related to the fibre source used – longer fibres make for a stronger paper. Papers can also have additives to improve strength.
A satisfactory degree of opacity is required in printing and writing papers to avoid show-through from the opposite side of the printed sheet. A degree of whiteness is also desirable as this affects the contrast of the image and the overall print quality.
Recycled paper is made with a proportion of cellulose fibres derived from waste paper. The processes and chemicals used to remove adhesives, inks and other contaminants generally result in a paper stock with very short fibre. This means recycled papers tend to be weaker than papers made using 100% virgin fibre. Recycled papers can also produce higher levels of dust than papers made of virgin fibre. They should therefore be used with care in photocopy machines.
Coated paper comprises a cellulose base coated in a layer of brilliant white material such as clay or calcium carbonate. It is generally used for the printing of coloured materials such as magazines, coloured forms and brochures. It has a number of features which affect its long term permanence; these include brittleness, yellowing and the tendency for papers to stick together when damp.
Standards Australia has produced a standard for permanent paper (AS 4003 – 1996) which recommends papers with appropriate chemical stability, but not the physical durability required by the Archives. Our own specifications include an additional requirement that strength properties must not substantially diminish over time. We advise the use of paper that meets our standard of archival quality, by granting permission for those suppliers to use our registered trademark – the National Archives of Australia registered watermark, for Commonwealth records with a long-term retention period.
Archival paper is formulated to have both the chemical and the physical properties to ensure it remains usable for long periods. Chemical stability is ensured through the addition of an 'alkaline reserve' of calcium or magnesium carbonate to combat acid degradation. Physical strength is ensured through the use of long, high quality fibre such as cotton or fully bleached chemical wood.
An environmentally preferred paper or paper product is one which, in its characteristics, manner of production and manner of disposal or degradation, is calculated to have less impact on the environment than a paper of comparable performance.
Documents and publications that will be kept for less than 30 years may be suitable for production on recycled papers. Examples of these records are:
Documents and publications that need to be kept for longer than 30 years (determined according to proper appraisal assessment) should be prepared on papers which provide both chemical stability and physical durability.
Examples of these records are:
Papers intended for photocopiers and laser printers have specifically formulated strength, surface, and moisture properties to meet the operational requirements of those machines. A paper should only be used for photocopying or laser printing if it is specifically formulated for these uses and is described as a copy paper on its packaging.
The selection of paper for printing and publishing is related to the end-use, and the performance requirements of the paper in the printing press and binding equipment. Where possible, publications to be retained for longer than 30 years should be printed on uncoated archival paper.
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