Deterioration refers to a change of state of any materials from the original form caused by interplay between the object and the agents of destruction. The different types of deterioration of the paper-based materials are reflected in wear and tear, shrinkage, cracks brittleness, warping, bio-infestation, discoloration, abrasion, hole, dust and dirt accumulation etc.
Chemical deterioration is otherwise known as pollutants which are gases, aerosols etc. Due to the hydrogen ion present in the archival materials (internal and external factors), the Archive suffer an acidity which causes deterioration of many valuable rare books and manuscripts and lead to their complete loss. Thus, neutralization of the acid contain of the archival material is essential. This is done by treating the archives with a base. The base varies according to the material composition.
AGENTS OF DETERIORATION AND DESTRUCTION
There are various chemical causes or agents which led to the deterioration and destruction of the archives
This is the process of natural decay in air which effects all organic materials. If such materials are stored in good environmental conditions, the process is normally slow, but is accelerated in oxidizing pollutants such as ozone (created in electrostatic copying processes)., sulphur dioxide, nitrogen dioxide and cleaning fluids. In paper it results in the breakdown of the cellulose fibre structure and the weakening of the paper. Its effect are unlikely to be significant and are not easy to distinguish from those created by acid deterioration, which is more likely to be the prime causes of decay in archival documents. Oxidation is most noticeable in cellulose acetate still and motion pictures film and microfilm (consist of a polyester or acetate film base upon which an emulsion is base), where it becomes apparent in the form of ‘redox blemishes’ or ‘red spot’.
- ACID DETERIORATION
Cellulose material are also liable to decay through contamination by inherent acidic components, by acidic materials used in their manufactures and by atmospheric pollutants, paper made from mechanical groundwood pulp which has a high lignin content or which has been sized by alum and rosin especially are liable for such deterioration because they contain high quality of acid. The first visible evidence of such deterioration maybe a slight discolouration, which progress in time through yellow to brown. At the same time the paper loses its strength and eventually becomes embrittled to the point when it crumbles when handled. The level of acidity or alkalinity in a paper is measured by its pH value measured in a logarithmic scaled numbered from 0 to 14 with 7.0 as the neutral point; number higher than 8 denotes acidity. pH maybe measured colour metrically with certain medical indicators or more accurately by potentiometric methods using electrodes.
- FUGITIVE DYES
Certain pigments used in inks, water-based paints, textile dyes, photographic dyes, etc. are fugitive and fade or change in time. The chemical change that take place is called crosslinking. These changes maybe accelerated by acidity, heat, moisture or light but for some colour photographic process fading occurs even when print or negative are kept in the dark. Several pigment especially those in fountain paint inks and felt tip colours are water soluble and should be fixed prior to any treatments which require wetting.
- SULPHUR DIOXIDE
The most common deterioration is caused by sulphuric dioxide present in the atmosphere. The sulphuric acid is larger in industrial environment. It is hazard to cellulose materials like paper, cloth and leather where iron, copper are present. The most familiar effects in libraries is the brown and brittle edges of books caused by sulphur dioxide.
Ozone act as a powerful destroyer of organic materials. It makes the colour of fabric book fades and the book binding materials such as leather, gelatin, glue and paste are also susceptible to deterioration by ozone in humid weather.
- ELECTROMAGNETIC DETERIORATION
Most electromagnetic signals eg. On audio, video and computer tapes are subject to gradual loss of strength. They are moreover susceptible to deliberate or accidental deletion, distortion, print through and over recording.
- ATMOSPHERIC POLLUTANTS
Gases, exhaust, dirt, dust and other pollutants come in the form of particles that float in the air. They are acidic and abrasive, and when they come in contact with the materials they can ‘eat’ through the materials causing them to deteriorate. Pollutants can cause metals to rust or wood products to chip and break. These pollutants can also damaged equipment and materials which then penetrate materials and promote chemical and physical deterioration
- OTHER CHEMICAL INSTABILITIES
A wide range of chemical instabilities maybe encountered by archivists and conservators, eg staining of badly processed photographs, destructive deterioration of cellulose nitrate bases of old till and motion picture films, hydrolysis of polyester films.
PREVENTIVE MEASURES FOR CHEMICAL DETERIORATION
Prevention and preservation plays a key role in preserving the archives. It aims to minimise the chemical deterioration of records and other Artefacts and to prevent the loss of information content. Preventive conservation should be practised to keep the documents in healthy, good and usable condition.
- One of the best way of controlling atmospheric pollutants is filtering of the air intake into storage areas, which can be attained by air conditioning system operation for 24 hours throughout the year.
- Avoid exposure to extreme temperature and relative humidity (high temperature accelerated the decay processes, cooler temperature slow them down; RH levels above 65%)
- Without this facility simple measures like wrapping the manuscripts in cloth or placing them in containers reduce the act of pollution to a great-extend.
- Good ventilation and air circulated system.
- Filtration device incorporated into air-conditioned system to remove harmful gases, dust and other particles.
- Proper and regular maintenance of system and replacement of filters.
- Chemical cleaning or bleaching should not be taken by non-conservative staff materials should always be tested before chemicals formulation are directly applied to the book or book cover since they may have adverse effect on the books as well as user of the books and staff of the library.
- Uncoated wooden storage should be avoided as it gives off volatile acidic vapours.
- Use vacuum cleaner and fine brushes for dusting of shelves and books.
- The books should be kept inside the cupboard as they are better protected then keeping outside.
- Chemically active components with archival significance eg. Photographs, acidic file covers should be removed and stored separately or placed within polyester sleeves.
There are many different reasons why records and archives deteriorated. Perhaps the most significant factor is the nature of archival materials themselves. Many records and materials and archives are composed of harmful chemicals they are inherent, fragile and prone to degradation of the archives. Thus, certain steps should be taken to protect the materials in archival storage but also to ensure the staff, researchers and office personal to handle records and archives carefully. Since preservation is crucial element in the whole operation of a record program, it is therefore necessary for record managers and archives to store record in condition that makes a records have a prolonged life. Selecting good quality materials will also help in preventive preservation that also seek to reduce risk of damage and slow down the rte of deterioration.
- Wringer H.W, Deterioration and preservation of library materials, Chicago: University of Chicago Press, 1970.
- Mukherjee, B.B, Preservation of library materials, Archives and documents, Calcutta, world press, 1973.
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