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 fibers 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 neutralize 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 fiber source used – longer fibers 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 fibers 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 fiber. This means recycled papers tend to be weaker than papers made using 100% virgin fiber. Recycled papers can also produce higher levels of dust than papers made of virgin fiber. 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 fiber such as cotton or fully bleached chemical wood.
Leaves of Borassus flabellifer L. and Corypha umbraculifera L. have long been used for the preparation of writing materials in India and other neighboring countries. They are still in use in many parts of Southern India. They are resistant to the attack of insects and are impervious to water, but the mode of preparation differs according to the species. They are highly preserved for their importance and the details for the society. In basic, they are highly naturally preserved from action of microbes.
Centuries ago, in many countries of Europe and North America, birch bark had been occasionally employed in writing short notes and letters. Bibliotheque Nationale in Paris has in its collection two letters on birch bark, one dated 28 June 1647 and the other dated October 1676. The earliest known manuscript on birch bark has been found at Khotan in Central Asia, and from extant records and literary descriptions it is now certain that this material was widely used in Central Asia and in the northern region of India in much earlier period of History. The historian of Alexander the Great, Quintus Curti us Rufus, while enumerating the various curiosities of India made the following statement: “Tender bark of trees takes the signs of letters just like sheets of papyrus”. This statement of Curtius dates back to the 1st Century A.D. but the information which it provides dates back to the time of Alexander’s invasion, that is, the 4th Century B.C. and since the material was widely used at the time of Alexander’s invasion it can be well assumed that the practice had been of much older origin. In India, the more recent manuscripts on birch bark in larger number come generally from Kashmir and other Himalayan regions, where birch trees grow in abundance. It is obvious that the use of birch bark, which in Indian language is known as ‘Bhurjapatra’ continued for a long time, even after paper was introduced in India by the Arabs in the early part of the 13th Century A.D. It is also obvious that it was introduced very early in history, although very few specimens of the earlier period are available, because of the deteriorating effect of damp climatic condition of the Himalayan region.