A document which has accumulated a lot of dust, has pencil marks or is otherwise soiled, spotted or stained, and is folded, requires cleaning, washing and flattening.
Techniques for the purpose require a good knowledge of the constituent materials of the document, together with common sense. Before applying them, the restorer should have clear idea of the document’s capacity to withstand such treatment.
Brush and compressed air
The basic method of cleaning paper is by gentle dusting with brushes which though time-consuming is effective and does not harm the document in any way. The process may be accelerated by the use of an ordinary household vacuum cleaner with brush attachment which is effective in removing dust from documents record volumes.
If, however, the number of documents in need of cleaning is large, the use of compressed air rapidly gives good results. The air is supplied by a compressor of 300-30 litres capacity in which the air is maintained at a pressure of 3-4 kg per sq.cm. a blow gun fitted with a pressure control directs a blast of air along the sides and edges of the volumes or bundles of documents in such a way that all free dust is blown off without damaging them. The full pressure of the air is never directed straight at the documents themselves. With controlled blast, even brittle documents may be effectively cleaned. This process is conducted in a specially designed air-clearing unit connected to a suction fan by ducts. Dust blown off by the blast of air is drawn away from the worker by means of the suction fan and carried to a chamber fitted with renewable cellulose filters which trap the dust particles, and the dust-free air is returned to the room. The filters themselves are cleaned by vibration; the dust settles at the bottom of the chamber and may be collected for analysis of the solid contaminants which it contains,
This air-cleaning equipment is costly and mainly used in institutions which have large holdings of archive documents and whose acquisitions are frequent and numerous. Satisfactory equipment for smaller holdings consists of an air-cleaning unit comprising a compressor, a tube fitted with a suitable nozzle and valve to control the blast of air and fume hood fitted with an exhaust fan. Dust-laden air is sucked in by the exhaust fan and expelled outside the building. This removes the need to employ dust-trapping filters.
Surface dirt and superficial soiling, pencil and finger marks may be easily removed by soft rubbers or other non-abrasive erasers, such as sponge rubber, art gum, soap, kneaded erasers and synthetic erasers of materials such as vinyl. Kneaded erasers are perhaps the most gentle in their action, removing dust and pencil marks as easily as a blotter soaks in ink. Viny1 eraser is also very easy to work with, although it has a tendency to pick up its own crumbs; like all plastic materials it should be used with care, as it has the ability to affect other resins that may be present on the paper of the document. It may, however, be safely used on printed documents.
A material often used and recommended is bread crumbs. This material does clean the paper, but if the crumbs themselves are not thoroughly removed after treatment they cause spotting on the paper
In addition to the erasers mentioned above, a number of materials used in the dry-cleaning industry have been recommended, for example ‘Opaline’ dry-cleaning bags and soaps. The Opaline dry-cleaning bag is mesh bag containing wither rubber or a dust eraser soap. Heavy films of loose dust may be removed simply by rubbing the bag gently over the surface to be cleaned. Its action is however, no stronger than that of erasers and it is useful rather for removing loose dust rather than fine particles embedded on the surface of the document. When the surface of the bag becomes dirty through use, it is twisted and shaken. The dust particles fall away, leaving a clear surface for re-use. Among other new materials mention may be made of a wall-paper cleaner available in cans from paint and hardware stores. Of the several varieties on the market, ‘Absorene’ has proved suitable for very large and dusty surfaces. It is similar in its use and effect to the kneaded eraser.
For cleaning with any of the erasers described above, the paper, which must be neither weak nor brittle, is held firmly. The eraser is then applied at the centre, and moved lightly in one direction from the centre of the sheet to the edge, to prevent the wrinkling and tearing which any other motion may provoke. After cleaning, all traces of crumbs are carefully removed from the paper. Otherwise, they result in further damage to the paper.
This process is useful in removing surface dirt, pencil marks and soil stains. More persistent spots or stains may be removed by washing or solvent treatment. Before subjecting the document to such treatment, however, it is necessary to remove all pins, clips and rubber bands. These should in fact be removed even if the document requires no treatment, otherwise they will leave their own stains on the paper. The deterioration of rubber bands leaves brown stains and corroded clips and pins are difficult to remove from paper and leave rust stains. Such stains are difficult to remove and often result in further damage to the document.
Washing is good for old paper, and has been observed to increase the mechanical strength of dry and brittle paper by re-establishing some of the broken hydrogen bonds in the cellulose molecule. Simple washing in clean, preferably distilled water helps to remove dark, soluble matter and some free acid from the paper. It also reduces water stains and permits the removal of wrinkles and other distortions. However, water has a tendency to ‘set’ surface dirt, which should be erased or removed by any of the techniques described above, before washing.
Some inks are adversely affected by water and these also require pre-treatment. The first step, therefore, should be to test the effect of water on the writing of the document. For this purpose, a little water is applied to the writing in a corner of the document and allowed to soak in. A blotter is applied firmly to the writing. If it becomes stained, it is clear that the ink is soluble in water. Such writing should be bathed with a protective solution of cellulose acetate in acetone and allowed to dry before the sheet is immersed in water. Printing inks and iron-gall inks are not affected by water and may be washed without any danger of running or smudging. Other inks, however, have a tendency to smudge and wash off and should be protected in the manner described above or with a 5 per cent solution of soluble nylon.
For washing with water, an enamelled tray, similar to those used in photographic work and large enough to accommodate the sheet is very suitable. The tray is filled to about half its capacity with distilled water. Prior to immersion in the water, each sheet is supported on plastic netting or if this is not available, on a waxed paper sheet. Brittle or broken sheets are supported on both sides to prevent damage or the loss of broken pieces. The sheets must be handled with great care. Thus supported, they are immersed by sliding them edgewise in water until they become uniformly wet. Ten sheets may be immersed together in this manner. They are then shaken gently several times and allowed to soak for a further 30-60 minutes. At the end of this period, the tray is gently rocked for a moment, and the soaked sheets are removed one by one by means of the supports and placed in an empty tray to drain off the excess water. They are then rinsed in clean water and dried carefully between clean sheets of blotter on a glass plate, pressure being exerted to remove the remaining water. The blotters are changed when necessary. The sheets are allowed to dry slowly in a gentle draught of air, and are finally allowed to dry completely under slight pressure between fresh blotters. Care should be taken not to apply excessive pressure as this imparts unequal characteristics to the sheet on drying. The drying process is completed by passing each sheet through a heated mangle or ironing by hand, the heat being applied to the document through the blotter and not directly. Finally, any protective coating applied to the writing is removed by sponging with cotton dipped in acetone. The process may be continuous if after each set of sheets has been removed from the washing-tray, another set is immediately immersed. The water in the tray should preferably be changed after each washing. Alternatively, washing may be done in running water. For removal of paste and glue, the water should be Luke-warm, and DE acidification (see Chapter 5) is advisable for removal of acidity in papers with a low pH.