Contents - Previous - Next


5. Methods of restoration

5. 1. The wet treatment
5.2. The possibilities of the leafcasting technique
5.3. The possibilities of the paper-splitting process
5.4. The lamination process - alternatives

 

The equipment used in restoration has undergone various changes in the last decade.

It is maked by the growth in 'knowledge through research into basic scientific principles and their being put into practice. efforts to structure conservational processes in a more efficient very has led to the results which will be outlined in the following but which are in no way complete.
It is quite evident that the results are the most impressive when it is in the form of international co-operation and exchange of information. The trend of using conservational methods, bringing quality and quantity into unison, is continuing.

The technical basics which the restorer has at his/leer disposal care now more comprehensive and greatly improved. At the same time one cannot overlook the fact that exaggerated commercialization and the range of conservational techniques and equipment have restricted the distribution of efficient methods.

5. 1. The wet treatment

Wet treatment (which consists of a succession of cleansings deacidification and buffering immersions and basic conservation) is particularly a big problem for extensively, badly damaged books because of the great amount of time and energy involved. Moreover, wet treatment is decisive for the quality and lifespan of the treated books and sheets.

The traditional manual wet treatment of paper suffers from some methodical shortcomings. Only in the rarest of cases can, for example, a large amount of single sheets be treated under absolutely the some conditions. The amount of time needed for laying the sheets, in and transporting them through the basins inevitably creates differences in the time the solutions need to take effect on single sheets or groups of sheets.

Thorough rinsing and checks on the procedure are measures which are not often taller in practice.

Deacidification sand the creation of an alkaline reserve generally occurs empirically without general checks as and exact stipulations on the measurement of the solutions. The often brittle state of the paper males the handling, of it bore difficult and means that special safe by precautions are necessary, which increases the wore involved. The danger that the restorer is exposed to, being in contact for often hours with the fluids and chemicals is a further problem under the circumstances which can only be reduced somewhat by protective clothing. All qualitative disadvantages of the manual wet treatment can be eliminated through a great deal of work with technical appliances in the workshops, but the quantitative results cannot be improved upon because of the limits of human capacity.

Mechanical wet treatment solves qualitative and quantitative problems and reduces the overall work in wet treatment. The plant at the Deutsche Bücherei in Leipzig consists of six basins arranged alongside 'each other, measuring 50 x 70 cm and 60cm deep. A transportation device, which allows for the horizontal or vertical transportation of the sheets is situated above the basins. The basins are made of steel filth a coating of vulcanized hard rubber. Every basin is provided Zenith heating, ventilation, a thermostat and are fully plumbed in wraith overflow. The whole plant is linked up to the central hot and cold water and compressed air systems. The compressed air pipe directly in front of the plant allows the introduction of CO2 gas. There is a control unit every three basins. Every basin has a pH value guage. The readings can be taken from an electrode switch on measuring instrument.

These technical pre-requisites quarentee exact and verifiable wet treatment according to individual requirements.

At the moment the following program can be carried out on the plant on the basis of tested procedure:

1. Water Basins of varying temperatures (between 20 and 100°C)

2. Oxydation bleaching using potassium permanganate

3. Neutralization sand use of call alkaline reserve using alternatively sodium tetraborate, magnesium or calcium hydrogen carbonate

4. Oxidation bleaching using hydrogen peroxide

5. Deduction of lignin in paper made from wood pulp using peroxide carbonates and potassium permanganates

6. Solution of glues, chiefly with starch And protein glues with the help of enzymes. As a kind of side-effect, the removal of the supporting sheets after the paper splitting process con be carried out in an optimum way

7. Basic conservation of all sheets of paper using p-hydroxdiphenyl methane.

8. .Re-sizing of the treated sheets with cellulose ethers or protein solutions.

The given examples can be varied and combined so that specific and effective wet treatment is possible - according to the kind of damage to be treated - making everything much more economic. The use of chemicals, the amount of water and energy consumed cord not least the problem of waste water have definite advantages over the manual procedure.

If one considers all the necessary steps in the process from the dismantling of the book to the start of the stabilization process as a complex, then a thought-out organization of work saves considerable amounts of time. The fact that the dismantling and dry-cleaning can be coupled with the formation and ordering of different groups of damaged books permits, apart from a sophisticated way of Working vita the wet treatment plant, a positive influence on the hygienic and micro-biological environment in the workshop. he pages to be treated are arranged in special sieve rolls after dry-cleaning and independent of the degree of damage. The sieve rolls consist of a wooden structure (comparable to the Wooden spool of a cotton reel) and two polymide sieves, one lying on top of the other. The sieve lengths are eight metres long and 40 cm wide. The course-meshed sieve is needed to keep the sheets of paper apart and is simultaneously the transportation sphere for the different fluids. The second, very fine-meshed sieve lies on top of the first coursemeshed sieve.

The sheets to be treated are placed on the course-meshed sieve and are covered with the fine-meshed sieve. The spool is then inserted on a simple winding device, and after the sheets are in position, the sieve lengths are rolled onto the spool. Varying amounts, on average 50 sheets (depending on format), can be accommodated in the sieve roll (which measures 40 cm wide and 16cm in radius). Two catches secure the sieve rolls which are then removed from the winding device. After fitting a new spool, the next sieve roll can be wound on. In these sieve rolls the individual sheets cannot slip around but remain perfectly secure so the different substances during the various stages of treatment can penetrate the sieves and reach every point of the sheets. In the whole duration of the wet treatment the paper sheets do not suffer any mechanical damage. The sieves guarantee rapid penetration and draining of the fluids and can withstand constant use over a longer period of time. Eight of these circular sieves (about 400 sheets) are placed next to each other in simple sheet containers. Once the wet treatment is over, the wet sieve rolls are opened and hung up in a simple drying frame. The rest of the drying process is achieved in a short time by laying the sheets flat and allowing them to dry at room temperature.

A system of wet treatment has been developed at the University Library of Jena which starts treatment smith dry, disintegrating books and finishes month chemically cleansed, disinfected and deacidified paper with a reduced amount of lichen. With this kind of wet treatment it is guaranteed that every individual sheet is fully rinsed because of the even adhesive effect on both sides of the paper so it is therefore not subject to any mechanical strain and is care fully dried in alarm air.

The cassettes for the wet treatment, which were based on a modular construction system, Allow a daily productivity of 1,260 sheets (large folio) or 2,520 sheets (folio). one cassette contains 70 polyester sieve bags which can accommodate the deteriorated printed matter. A 150-litre steam-boiler can supply three cassettes. then the wet treatment has come to an end, the cassettes are extended to a length of 150cm by fixed pieces of dwelling. Four extended cassettes can be dried on trolleys with shelves.

The advantages of the cassettes for the wet treatment are:

- maintenance-free use, high efficiency
- saving of additional Cardboard, filter cardboard and filter paper for drying
- reduction in the amount of spores of micro-organisms which attack paper in the workshop
- the conditions necessary for lignin reduction and enzymatic beet treatment (even rise in temperature during the treatment are guaranteed.

In conventional wet treatment, decaying stock is treated between supporting sheets and sieves. Due to this fact, it is subject to uneven rinsing and harmful currents. The adhesive action on both sides of the paper between support papers and the original material does not exist. The horizontal method of treatment is possible on single sheets and stable paper.

Lignin reduction in wood pulp paper or the systematic removal of the gelatine coating of split paper would, within the programme of mass treatment, with conventional horizontal wet treatment lead to uncontrollable damage to the materials.

There are years of practical experience behind the procedures and aids described above. Both protective systems mentioned above in the form of sieve rolls and sieve bags complement each other and fully cover the needs of wet treatment.

5.2. The possibilities of the leafcasting technique

Putting the composition of the fibres aside, paper s strength comes from the felting of fibres against each other, from the adhesion between the fibres and the formation of bonds between them without any glueing process being involved.

The procedures of making normal paper form the theory behind the principle of leafcasting.

The damaged sheet is laid on a piece of permeable material which is comparable to a paper-mould used by a paper-maker. The pulp, which is greatly thinned doves, comes onto the piece of paper and is sucked downwards through the sieve. The piece of paper on the sieve creates a barrier for the stream of pulp so that the single paper-fibres can only settle on areas of the sieve where there is no obstacle to the stream of pulp. The missing parts of the page and all exposed parts of the sieve become covered with matted fibres, that is, new paper. The hay this principle functions is influenced by different factors - the kind of sieve, the state of the fibres, the strength of the vacuum etc.

The leafcasting method is an internationally widespread way of filling missing parts of paper, and can be seen as an important development in recent years. In the seventies leafcasting devices were constructed on the basis of simple manual processes, which filled holes in paper with the help of paper fibre suspensions.

These devices can treat a number of sheets in one step depending on the size of the work surface. The Leningrad leafcasting device is the most efficient device of its kind because here the peripheral work, such as the preparation of the fibres and the further treatment of the restored sheets of paper to the book-binding stages, is all integrated. Leafcasting, as a kind of stabilizing technique, can, particularly in the case of mechanical damage, produce excellent results, which are also acceptable from the economic point of view. The need to mechanize restorative work processes, to overcome the problem of mass restoration, led to the development of the Copenhagen device. Per Laursen and Lars Gronegard developed a leafcasting device which facilitates the leafcasting process to function non-stop. The four-metre long machine consists of a frame for the moving paper sieve and the leafcasting unit. The damaged sheets are placed on the sieve, pass through the leafcasting unit and can be taken off the sieve, fully restored, at the other end of the machine. The relation between the concentration of the fibre pulp and the speed of the "sieve conveyor belt" is decisive for the leafcasting process. The time-consuming factor of having to ascertain the amount of fibres necessary for every damaged sheet of paper becomes super with the Copenhagen device. A photoelectric cell in the pulp basin guarantees that the concentration of fibre material stays constant but may be regulated. The passing of the damaged sheets through the leafcasting device depends on the speed of the sieve conveyor belt and the format of the sheets, but should take between four and ten seconds.

The expert can easily see that in this way the leafcasting process may be made more rationalized, taking into account the importance of mass restoration.

The restorer John F. Lowery of the Folger Shakespeare Library in Washington has developed a highly precise system for particularly difficult leafeasting work, such as the restoration of paintings. A manual leafeasting device is linked up to a video camera. The camera detects the missing parts in the original and transfers the results to a computer so that the necessary amount of figure is determined quickly and exactly.

5.3. The possibilities of the paper-splitting process

Interest in paper-splitting as a method of restoration for decaying books has rapidly grown in recent years. Nearly every restorer is well-informed on the principle of paper-splitting. Technology is diverse and the results in restoration differ. Paper-splitting is the most demanding technique for the restorer. It is linked with complicated operative work on the inner substance of the paper. Only through years of training, a great deal of concentration on the cork and care can guarantee that every piece of material threatened with decay can be restored to its original state. This kind of specialized technology may be mastered by restorers with many years of practical experience.

Otto Wächter referred to possibilities of neutralizing and generally stabilizing decaying material and that the paper splitting process which has been further developed in the GDR is "...at the moment the most sound restoration process for rotten, decaying paper which has been eaten away by ink...".

This remark refers to the true-to-the-original restoration of irreplaceable rarities and to mass restoration of other materials.

The paper-splitting technology which has been developed in the GDR is the result of many years of work done by restorers of the Deutsche Bücherei and the University Library of Jena. The present level of work and the technological forerun are thanks only to the two establishments, The reason for this success is not so much due to the splitting process itself, which takes a matter of seconds, but much more to the whole field associated with restoration, The considerable reserves of increased capacity can be attributed to the preparative and evaluative work to the technological specialization and the willing application of the leading restorers. here are the following basic principles for the paper-splitting process developed in the GDR:

- Paper-splitting as a part of general restoration, guarantees true-to-the-original maintenance of print, inks, colors, and structure of the paper fibres. The increase in the paper thickness by general inner stabilization is not as great as with other methods of restoration (lamination with Japanese paper, chiffoning or lamination in synthetic materials).

Paper-splitting must be reversible for future generations without causing them too great a loss of material or too much inconvenience materially or technically. Priorities aimed at include the use of materials which are resistant to ageing.

Taking into consideration the present level of knowledge in the field of paper-splitting, any reserves in capacity which have still not been fully exploited may be developed, even in restoration workshops of different kinds. For reasons of efficiency and quality, perfect paper-splitting concentrates on three independent kinds of device which ore nevertheless organically bound to one another.

The sophisticated equipment used in the wet treatment, in leafcasting and in paper-splitting is very expensive. This means that smaller and middle-sized workshops are often overstretched from the point of view of staff, space and money. Pith the greater employment of machines in the field of paper-splitting, the realistic aspects of business management such as the cost/profit ratio have to be increasingly taken into consideration.

Recent research has shown that paper in danger of decay, of varying thickness, with holes and different formats lends itself perfectly to the paper-splitting process using the adaptable and non-adaptable method. The subsequent paper splitting and general stabilization is characterized by great sayings in material, working hours and continuous step-by-step production with the sheets of paper which have been treated in the leafcasting process.

The development of a paper-splitting machine in the Deutsche Bücherei, Leipzig, has been successfully and constructively concluded. Efforts to find a partner for the construction of the plant in Leipzig are fully underplay. The first batch of special materials for the construction have already arrived in Leipzig. At present preparatory work is going on to match up the Per Laurson leafcasting device to the paper-splitting machine.

5.4. The lamination process - alternatives

The use of lamination as a way of stabilizing library and archive materials can be seen as a contraversial process of preservation. On the one hand it is classified as "ultimo ratio" and on the other hand as an acceptable method of preservation. Putting all the different attitudes aside, the lamination of paper with different kinds of synthetic materials is internationally a Widespread practice.

Generally, the surfaces of the paper are covered With a layer of foil, that is, the foil covers the original With a homogenous layer, of which only a small part is melted to the surface of the paper. Furthermore, it is also possible to impregnate the original with foil. In this case, the melted thermoplast penetrates the whole fibre structure of the paper and is hardly noticeable on the surface of the paper. This kind of stabilization requires the paper to be quite stiff and thick, since otherwise the paper loses its opaqueness and takes on an unpleasant transparent quality. The third possibility consists of using the lamination foil as a melting adhesive, if for example, materials sensitive to water are laminated with a foil interleaf together with a new backing material. The effects of lamination, impregnation or coating always depend on certain conditions such as pressure, temperature, time, the thickness of the foil and the state of the original.

The originals which are to be laminated should undergo a preparatory phase. This preparatory phase has a significant influence on the durability of the laminate. Firstly, as part of the usual treatment, everything is done to delay the natural ageing process of the paper (cleansing, neutralizing, alkaline reserve etc.). The inner causes of paper-ageing are of primary importance in the laminate because the exterior causes are to a great extent ruled out through the lamination process. Furthermore, the lamination process is irreversible, so that although de-lamination is possible, access to the original is no longer possible. Although it is possible to separate different types of foil from the original, using organic solvents which may be successful in some exceptional canes, this cannot be said for the majority of laminates. It is reasonable to expect that the precautions taken according to the present level of knowledge when using the lamination method is a necessity of conservation. The optical phenotype of laminates is, to a large extent, determined by the foil and the isolation material used in the treatment. The isolation materials prevent the surfaces of the laminate from sticking to the heated plate of the laminator. Depending on the surface structure of the isolating materials, the laminate surface can appear smooth, shiny or hardly perceptible. If a thin sheet of Japanese paper is laminated onto the surface together with the foil, the durability is improved and the surface of the foil takes on a matt appearance. 'nine depth of the structure is important to- the finish of the laminate surfaces then using textured release sheets. They should not be more than 1/4 of the thickness of the foil, because otherwise the laminate surfaces vile be too thick nod the remaining surface thickness of the foil over the original Will be partially too thin.

Obviously in previous years there has been a growing trend to rep' ace lamination as a way of stabilizing paper Smith other alternative methods. These alternative methods should be of a more conservational nature whereby paper is protected, strengthened and its use is prolonged, but also so that the original is not irreversibly fused to the foil. The process of encapsulation, developed by the Library of Congress, is able to do this. The original is placed between two sheets of polyester film Which is sealed on all four sides. In this way it is protected, strengthened and still usable. If necessary, the original con still quite easily be removed from the "envelope" Similar methods can also be put into practice - for example with industrially manufactured envelopes made from polythene foil. With these kinds of materials a slight electrostatic charge is built up between the original and the material of the envelope, which prevents the paper from slipping around.

It is quite obvious that these kinds of methods, when well-organized, are much more efficient than normal lamination processes.


Contents - Previous - Next