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5. Bindings

5.1 Definition and composition
5.2 Tanned hides: definition and composition
5.3 Deterioration factors and preventive measures in the case of tanned leather
5.4 Restoration techniques: materials and procedures

 

5.1 Definition and composition

The specific function of bindings is to protect the book while in use or while it is being stored.

The most remote forerunners of bindings could be said to be the simple cloth bag, which was used to contain and protect papyrus scrolls. But although the function was the same as that of bindings, it was not until the Romans adopted the square format for their books that protective coverings could be regarded as bindings as such.

The earliest binding was nothing more than a row of stitching which joined the pages or sections of the book, fixed between wooden covers or a sheet of parchment by means of pieces of cord known as ribs.

At first the covers were plain but they soon began to be ornamented and the ornamentation became increasingly important until it reached a point when it became a reflection of the fashions and artistic tendencies of the day.

So, binding, which was born out of a practical need, became an artistic and documentary element.

The restoration of a binding is, therefore, determined in the light of its artistic appearance, although its functional aspect vis--vis the book must not be forgotten.

Bindings comprise the following components, and although variations may exist, the basic elements are generally the same and they are arranged in a more or less repetitive fashion. This layout is called the "architecture of the book". The most important parts of a binding are:

Boards: pieces of wood, board ... which cover the book;
Cover: material used to cover the boards, usually leather, cloth, etc.;
Spine: outer edge of book to which the pages are attached;
Stitching: method by which the pages are joined
Top-, tail- and fore-edges: planes formed by the edges of the pages;
Flap: edge of the book cover which protrudes beyond the body of the book;
Joint: grooving along the spine where the boards are attached;
Channel: triangular groove in the boards to bind the leather to the joint;
Ribs: tapes or cords to which the stitching is attached and which join the book to the boards;
End-papers: sheets of paper or cloth inserted at the beginning and end of the book and covering the inside of the boards;
Headband: thread or cord placed at the top and bottom of the spine to protect the corners of the sections.

Apart from these essential elements there are many others which further reinforce the binding or whose function is merely aesthetic (hasps, corner bands, ornamental studs, binder's title...).

5.2 Tanned hides: definition and composition

The origin of tanned leather is very remote and this material has been used for a variety of applications for at least 50,000 years (clothing, containers,...). With the passage of time, it came to be used as a writing surface and today it is one of the main elements in binding.

Leather, tanned and untanned, has two distinctly different surfaces: the skin side - uniform, compact and darker - is the outer surface of the dermis; the fleshy side, clearer in colour and spongy in appearance, is the inner layer.

In the natural state, skin is a highly flexible and adaptable covering due mainly to its capacity for regeneration and the balance of its components. But when the animal dies it begins to lose its properties, especially those of a mechanical nature, which can only be maintained by means of manufacturing processes that will ensure stabilization.

The problem with leather is that as it loses water it loses the element which holds the collagen fibres together; something must be put in its place to renew this process and restore lost flexibility. This is what the various tanning methods do.

Before tanning a hide several operations must be carried out: the hide must be dried out in brine so that it may be conserved until the tanning process; it must be soaked to soften it and remove salt (today this is done in rotating drums); it must be limed so that hair can be removed more easily; it must be scraped to eliminate fatty, animal tissue which may still be adhering to the hide; and finally it is steeped so that the hide will lose its alkalinity and be protected against attack by micro-organisms in former times this was done with the use of manure, whereas today enzymes are used.

In the case of mineral tanning a bate is also used as a temporary preservative; the products used are sulphuric acid which removes the lime from the hide and sodium chloride which eliminates the swelling produced by the acid.

There are four methods of tanning: animal, vegetable and mineral tanning, and tanning using synthetic agents.

Animal tanning is the most primitive method, involving the chewing of the hide. The action of the enzymes and the manipulation give the hide flexibility. The application of fish-oil-based lubricants enables the fibres to move freely and similar results are achieved.

Vegetable tanning is the classic tanning method and the one most suitable for binding purposes. The tanning agents are tannins obtained from plants such as the oak-tree, acacia, horse chestnut, silver fir... At first these substances were simply applied by direct contact between the wood and the hide. Today the method is much more sophisticated: acid baths allow the tannin, which is commercialized in powder form and applied in baths in rotating drums, to penetrate more easily.

Tanning using tannins is ideal for binding purposes as the skin is easily moulded to the contours and will accept printing and gilding.

In mineral tanning tannins are replaced by chrome, an element which gives the leather cohesion and flexibility, as the collagen chains are reinforced. Two baths may be used, the chrome being applied in the form of acidified sodium bichromate with sulphuric acid and neutralized subsequently with sodium thiosulphate. Alternatively, the process can consist of a single bath with chrome sulphate as the base, in which case reduction takes place in the bath itself before the hide is put in.

From the physical-chemical point of view, chrome-tanning improves conservation but it is harder to work with and printing and gilding are more difficult.

Commercially it is more viable as the tanning process is rapid, requiring only one week, as opposed to ninety days in the case of the use of tannin.

Synthetic tanning is not common in the case of leather for binding. In this process phenol-aldehyde sulphonate and lignosulphate of magnesium are used. These are obtained from cellulose residues.

Once tanned, the hides may be dyed and lubricated and even varnished to make them more flexible and resistant (in this case vegetable, animal or mineral oils and specific resins are used).

In general, it can be said that tanning is an irreversible process which inhibits protein hydrolysis, reduces attack by micro-organisms and improves the mechanical qualities of the skin, making it softer, more flexible and more resistant.

5.3 Deterioration factors and preventive measures in the case of tanned leather

Tanned skins are a much more stable material than untanned hides. Due to tanning the protein materials are not affected by the physical-chemical reaction provoked by water which means that they are less liable to suffer alterations due to hydrolysis.

Despite these advantages, the skin is also sensitive to extreme climatic conditions and in overdry climates it becomes hard and cracks whilst in very humid climates it may rot.

The tanning process also inhibits biological attack to a considerable degree, whether due to mildew or insects, but it does not stop these attacks from proliferating if the conditions are right, especially by micro-organisms. These are encouraged when the relative humidity rises above 68%, and in this case fungi and bacteria produce stains and weaken the skin. In the case of skins used for binding, attack by insect pests is quite common and may lead to the work being perforated especially in the spine area where there are appetizing substances such as natural adhesives. With regard to preventive measures, see the references to paper in section 3.3.

Another advantage of tanned leather, as opposed to untanned hides, is its improved mechanical properties. This means greater flexibility, softness and resistance but, in the case of skins used as covers in binding, mechanical alterations are common if the books are poorly stored and liable to be damaged by rubbing and scratching.

Poor binding can cause broken joints just as excessive weight and size lead to various types of damage arising from use.

In addition to the recommendations applicable to paper preservation, it should be pointed out that a well-lubricated extremely flexible skin will prevent this type of damage to a certain extent, especially along the joints.

Mention has already been made of the different tanning methods, each of which gives the skin specific properties. As has been pointed out, skins used for binding were tanned using the chrome or, preferably, tannin method. Chrome-tanned skins suffer fewer alterations of a chemical or biological nature and are virtually unaffected by a phenomenon which is quite serious in the case of skins tanned using tannin - acidity.

Acidity arises due to the presence in the atmosphere of sulphur dioxide which, catalyzed by metallic particles in the skin itself and aided by the humidity in the surrounding air, forms sulphuric acid in the skin and, in combination with oxygen, makes the skin brittle especially in those areas which have greater contact with the atmosphere (spines).

Keeping the books in a pure environment or in sleeves or jackets reduces this problem to a large extent.

It has been proved that leather with tannin is more sensitive to atmospheric pollution when any type of washing process has been applied, because non-tannic substances soluble in water - which protect it against chemical agents - are thus removed. It is better then, to use skins which have not been washed after the manufacturing process (e.g. during dyeing). However, this problem is solved if the freshly tanned or washed skin (i.e. before chemical attack has set in) is treated with protective salts which will replace the lost substances. This treatment is carried out by impregnating the leather, either by spraying or using a sponge, with potassium lactate (50 g. in 1/2 litre of water).

5.4 Restoration techniques: materials and procedures

The same criteria should be followed for restoration of bindings as for other graphic documents (Chapter 1) but cases frequently occur which raise doubts as to the correct procedure.

In general terms it may be said that four situations have to be taken into account.

1. the case of bindings which are useless due to their limited documentary value
2. lost bindings
3. bindings without the book
4. deteriorated and irreplaceable bindings

5.4.1 Useless bindings

This is the case of many modern limp-bound books the pages being simply stuck with glue and the covers made of thin card.

In these cases the best thing to do is to replace this binding with a more functional and resistant type as it must not be forgotten that one of the main functions of the binding is to help conserve the book.

The pages should be unstuck, the glue cleaned mechanically and then the pages should be sewn using a felling stitch. This is the only way to stop the pages from becoming detached in a very short time.

A less costly solution is to reglue the pages using a polyvinyl acetate adhesive. In this case the glue is spread right and left with the spine fanned out so that the adhesive can penetrate a few millimetres into the edges. To make the join stronger still, a few transversal grooves should be made in the spine using a saw (in such a way that the cuts are oblique) and tapes or cords should be inserted into the cuts as ribs. The angle of the cut will stop them from becoming detached.

After these operations have been carried out, the book should be bound; the covers should be of a material and colour which will harmonize with the original. The most common solution is to superimpose the old cover on the front board. In some instances, however, it is preferable not to do so and the old cover may be inserted in a pouch under the new board, to serve as a record. It may also be included in the book as a kind of title page following the preliminary pages.

5.4.2 Lost bindings

This is a fairly common occurrence which presents considerable problems as to the criteria to be followed. When there is no information available on the old binding, the book should be bound according to the style of the period and the characteristics of the book but its appearance should be discreet, that is to say, any special or out-of-the-way features should be avoided. It must be remembered that the purpose of a new binding is to conserve the book and the temptation of producing an artistic binding designed to rival the importance of the work must be avoided.

Neither should it be forgotten that to avoid any risk of falsification, all the materials and techniques used should be modern, provided that they harmonize with the whole and do not present a problem for future conservation.

When there are descriptions, drawings or photographs which document the appearance, techniques and other elements of the original binding, a similar mounting should be aimed at but always using modern materials and techniques to avoid any "faking"; in this case it is absolutely necessary to include a note giving the sources of information on the old binding. Normally this is inserted in the book itself as an appendix or in a discreet place such as a pouch under the back cover.

5.4.3 Bindings without the book

This case does not arise too frequently but bindings may be found without a book due to a variety of causes such as attack by insects, physical agents, or simply collectors keeping the bindings but disposing of the text.

When this situation arises there are two available solutions: to make up a book with blank pages or to create a kind of model.

In the first case good quality paper should be used in keeping with the type used in the period to which the binding belongs. Stitching and all the other lost elements should be done according to the same criteria (good quality and in harmony with the whole but avoiding any risk of "faking").

The other solution, perhaps more attractive, is to place the binding over a transparent perspex structure which simulates the form of a book. In this way, without adding anything, the idea of the old book is suggested and due to the transparency of the model information is provided on the internal structure. This system is ideal for exhibitions.

Another possible solution, of a rather incomplete kind, is to restore the cover and whatever material is left of the old binding and keep it in a polyethylene sleeve. This ensures preservation but removes the aesthetic and functional value.

5.4.4 Deteriorated and irreplaceable bindings

This is, statistically, the type of binding most commonly found in restoration workshops. In this case the means at the restorer's disposal should be used to restore the original state and functional nature of the binding conserving as many old components as possible. The most essential lost parts should be reconstituted following the criteria laid down throughout these pages.

The steps to be taken in restoring bindings, omitting those which are identical to paper restoration (analysis, photography, insect removal, disinfecting), are the following:

5.4.4.1 Dismantling

This phase could be included in the analysis stage as what the restorer has to do is study how the old book was put together and how its various elements were laid out so that it may be re-assembled in the same way. Diagrams, photographs and other data must be used; memory must never be relied upon.

The book should be dismantled very carefully and this procedure should be regarded as real research work for it helps the restorer to see how books were bound in a given period and in a given place.

The first step is to number the pages so as to prevent them from being wrongly placed. This is very important especially with very old books, where the pages were not always numbered correctly. A soft pencil should be used for this and the number should be placed on the bottom inside angle of the page. This is a not very conspicuous place and it is usually stronger than the outside corners which are liable to be damaged when the numbers are rubbed out after the treatment.

A pencil is the best tool for this job as it is easily rubbed out and it does not alter during the processes of washing or bleaching the pages.

Pagination should begin with the first page of the book (even although it is blank) irrespective of the old numbering.

Example of a diagram for a document comprising three sections of four pages each.

1 2 3 4 5 6 7 8 9 10 11 12    
                      9a   11a
o                   * *   o
- - - - - - -

o = loose page,
- - - - = page loose but originally joined,
= fold,
8- - -= page missing

Once the pages have been numbered the book may be taken apart; it is advisable to start by cutting the ribs at the point where the boards are joined to the book itself. If the stitching is in good condition and the restorer wishes to conserve it, the ribs should not be cut but detached from the boards.

If it is necessary to resew the book the text should be dismantled. The first stage is to remove the headbands and spine liners. The headbands should be saved, if possible, for subsequent replacement. Should they be in a poor state of conservation, what remains should be kept as a sample of the material and the manufacturing process originally used.

Paper, mull or cloth used to reinforce the spine may be removed by mechanical means, using a scalpel. Although moistening would facilitate removal there would be a risk of softening the glue and staining the sections along the joint flange. If the book has to be washed this is, perhaps, of lesser importance as the stains usually disappear with a water and detergent bath. If mechanical cleaning is not sufficient the spine may be moistened slightly, care being taken to ensure that this does not affect the sections.

To facilitate the removal of any glue remaining on the spine, it should be tapped lightly and shaken so that the crystallized glue fragments and falls off. The restorer should not persist with this operation if there is any risk of tearing the pages.

Before unpicking the book, a diagram of the original stitching should be made so that it can be reproduced later. These details should be noted as the book is being taken apart, or better still, beforehand, each section being examined individually.

Diagram of the two most common stitches.

To unpick the book the threads surrounding the ribs which can be seen on the spine should be cut. If only some of the sections are to be dismantled or the stitching is to be analysed while being unpicked, the centre of each section should be located inside the book and the threads cut one by one. If part of the stitching is to be conserved, it is recommended that the book should be unpicked by passing the threads through the corresponding stitching holes. In this way a long thread is obtained to which the new thread can be joined.

In order to separate the sections without any risk of tearing their outer leaves, it is preferable to lay the book flat on a smooth surface and hold down the sections at the centre of the edges so that the pages are all level. The sections are turned over and pulled out gently with a few tugs. If the edges of the pages are fanned out, all the force of pulling falls on the outer sheet which will probably tear.

In the majority of books there is a numbering system which indicates the order of the sections (the signature). By taking advantage of these marks it is easy to locate the beginning and end of the sections and the position of the corresponding pages.

With regard to dismantling the boards, all the components should be separated as required and their position recorded. Samples of materials in poor condition should be kept; it is often useful to make a replica model to avoid error.

5.4.4.2 Cleaning and restoration of sections

Once the sections have been separated, any glue that remains should again be cleaned off using a scalpel, first with the section folded, just as it emerged from the book, and then, if necessary, with the outer pages separated and open.

If the pages do not have to be treated, possible deformation of the joint flange can be avoided by flattening the sections on the edge of a table, and then pressing the whole book.

It frequently happens that due to the state of the book itself or to the process of cleaning the sections, some pages may become separated at the central folds, especially in the case of the outer sheets.

If there are only tears or small gaps both pages can be joined together using a strip of tissue or methylcellulose. In the event of larger gaps, patches will have to be inserted.

The problem of restoring pages using tissue is that, if a large number of repairs have to be done, the spine will become too bulky. To avoid this, restoration should be as limited as possible and small tears should be left unjoined if they can be held together well enough by applying glue to the spine.

Sometimes, to save time, the tear in the outer sheet of a section may be repaired by laying the loose page on the following sheet and applying a little adhesive to the edge. This is the solution which is usually adopted by the majority of binders but it is not ideal as it does not respect the former structure of the book.

When the preliminary pages are lost or useless, their replacement does not pose a problem; paper similar to that used in the rest of the book should be sought (watermarked or continuous, bone-coloured or white...) ensuring always that it is of good quality.

Should an inner page be missing, the restorer may either not replace it at all or may replace it with a blank sheet of similar characteristics. The latter procedure is the more correct for, if the book is dismantled, it is easy to see from the structure of the sections if one or more pages are missing whereas this is difficult to ascertain when the book is left as it is. In this way the reader will have complete information concerning any gaps in the work.

Moreover, if the missing page made up a folded sheet with another page which is conserved, the latter will always remain in place better if it is joined to another and sewn in the normal way.

On occasions when another identical original exists, the missing page may be replaced using a copy obtained from the other original, although it is preferable that this copy should not form part of the book itself but should be added as an appendix to avoid any doubts concerning authenticity.

The process of restoring sections is completed with the pressing and stitching of the book; the stitching should imitate the original.

5.4.4.3 Stitching, glueing, headbands and spine

The most suitable procedure is to respect the original stitching but, if the book was unpicked to treat the leaves, it will have to be restitched. The new stitching should imitate the old and make use of the old stitch holes. Linen or hemp thread is to be preferred (the latter is particularly recommended for ribs) although materials similar to those used in the original should always be sought.

Sometimes, only the first and last sections are unpicked, either because only that part of the book needs to be treated or because with time and use they have come loose. When this is the case, complete new stitching is not necessary; a new thread can be added to the old one and the sections which have become separated can be re-sewn. If part of the rib is missing or in poor condition a hemp cord should be stuck on to the original (resistance will be increased if a nylon thread is passed underneath), a linen thread is added to the original stitching and the restoration is completed using single stitching as it is more resistant.

If the old stitching is inadequate and does not allow the book to be opened or increases the size of the spine excessively, it should be replaced for functional reasons at least, although evidence of the former stitching should be left. This is done by loosening the old stitching (even if a section or two have to be unpicked) and joining the sections using modern stitching. This new stitching may be done on tapes laid on top of the old rib.

There are many types of stitching. In general, single stitching is used to give the book greater strength, and double stitching when there is a risk of increasing the bulkiness of the spine due to the thickness of the thread or because too much tissue has been added when the sections were restored.

A subsequent stage involves the glueing of the spine. This is usually done using polyvinyl acetates but, despite the excellent properties of these adhesives from the preventive point of view, they have the disadvantage of being reversible. For this reason the use of natural adhesives is advisable, provided that when they are being prepared substances are added which will prevent attack by biological agents (e.g. orthophenylphenol). Flour paste treated with fungicides and bactericides is the best adhesive to stick leather covers.

As has already been pointed out, the headbands should be conserved so long as they are in an acceptable condition. If they are in poor condition and there was no option but to dismantle them when the book was unpicked they should be replaced by new hand-made headbands of similar characteristics. Frequently the headbands that have to be remade originally had a sheepskin base. If this is not too visible it is better to replace it with hemp which alters little with the passage of time.

Regarding the spine, the best material, due to its harmlessness and resistance, is Kraft paper. It is also advisable to use mull and, if cloth must be employed, it should preferably be a cotton fabric.

The best material for spine liners is a fine flexible cotton fibre board.

5.4.4.4 The boards

The boards, which are generally of poor quality and do not affect the aesthetics of the whole as they are normally concealed, are usually replaceable.

When, as a consequence of washing, the pages of a book increase in size, the old binding may be too small, in which case the boards will have to be enlarged.

From the conservation point of view, old millboard or wooden boards do not give good results. A good criterion to follow is to replace them with neutral millboard or plywood respectively. Plywood does not warp and due to its being glued it is less susceptible to attack by insect pests. Another excellent material used today as a substitute for board is methacrylate or PVC laminate. These materials are completely harmless and their conservation is totally satisfactory. As they are hidden they do not present any aesthetic problems.

To facilitate dismantling at a later date, neither the covers nor the end-papers should be stuck directly to these materials. A sheet of good quality neutral paper or card should be stuck to the methacrylate or polyvinyl acetate using contact glue or synthetic adhesive and then to the cover and end-papers using starch paste.

A material which was frequently used for boards is so-called pasteboard. This is made by sticking numerous sheets on top of each other so as to resemble cardboard. Normally valueless documents or remains of books were used. The pasteboard used for books should never be thrown away as those papers which were valueless in their day may, with the passage of time, acquire great importance for researchers. The leaves should be unstuck, washed, restored and included as an appendix with the corresponding restoration notice.

Sometimes the wooden boards have to be conserved, especially when the original binding does not have a cover. In this case they should be treated with insecticide, as they are the part most prone to attack by pests and can be a source of contamination for the rest of the book.

When there are traces of attack by insects, the boards should be consolidated using wood mastic preferably in a vacuum or by filling in the holes with a syringe. Polyvinyl acetate as well as epoxy and polyester resins are also used for this purpose; these materials are ideal as they do not shrink during the drying process.

If the wood is warped it may be straightened by inserting wedges which will be more effective and resistant if they are lozenge-shaped or can be dovetailed. This same system is also suitable for joining pieces together.

Finally, the wood may be coated with a slightly insulating material with a microcrystalline wax base.

5.4.4.5 The covers

The covers should be restored in the light of the material used and the degree of deterioration.

Patches must always be made using a material similar to the original and a very common solution, used both for cloth as well as leather covers, is to lay the old cover on top of a new one which will fulfil the real function while the original will serve purely as a record.

As the joint flange, edges and corners are the areas which deteriorate first, the old cover is cut into three pieces the spine, and the two covers - and is usually mounted on top of the new one. The cover flaps are usually eliminated unless they are in very good condition or are decorated on the inside corners.

Placing the old cover on top of the new one avoids having to patch the gaps.

Another relatively common problem which affects both cloth and leather covers is the increased size of the book after washing which implies the need to enlarge the boards and covers. The solution is very simple and involves using the material folded under the covers, provided that the flaps remain covered.

The most common covers are leather; this material is prone to attack by insects. The same precautions should be taken for the elimination of insects as indicated for parchment (4.3.1).

Removing the leather cover does not usually present problems, especially if the board is made of binders board. By gently pulling it away and finally using mechanical methods (scalpel and sandpaper) the remains of the board and the adhesive may be removed. Sometimes the process of lifting off the covers is aided by applying moisture but great care must be taken to ensure that the leather is not affected.

When the boards are made of wood, there is a risk of tearing the leather, if the cover does not come away easily. One rather obvious solution is gradually to trim the wood until the leather comes away.

The problem is greater with the overlaps folded under the covers, for they may have hardened and will crack when an attempt is made to turn them back in order to remove the cover. The most appropriate course of action is to use lubricants (see further below) or to moisten the folded area slightly, immediately applying size (there is a risk that the moisture may stain the cover).

The covers should be cleaned using neutral soap or oxgall. Both are rubbed in with a cotton swab or cloth.

A specific treatment for leather is lubrication, which is intended to make the leather more flexible by the application of greasy substances which penetrate the fibres, making them more slippery and preventing cracking and hardening. The lubricant is rubbed into the leather. No lubricant should be applied too freely because of the danger of staining the leather. The best thing is to use a well wrung-out cloth and rub the leather once it has dried.

The most commonly used products are cedar and ox-foot oil, Canadian balsam, nutritive creams, lanoline, coloured waxes, bitumen and natural waxes with fungicide, microcrystalline wax, polyethylene glycol. The use is recommended of lanoline or wax 213 which penetrates the leather and wax 212 or a similar product which remains on the surface as a protective layer. Plenderleith recommends the British Museum treatment based on anhydrous lanoline (200 9), cedar oil (30 ml.), beeswax (15 9.) and hexane or petroleum ether (330 ml.).

In the restoration of leather, vegetable tanned skins are to be preferred. For small patches or holes made by insects leather pulp with flour paste should be used. For larger insects the original leather should be pared down on the fleshy side (the reverse side) until the skin side of the leather is reached along the edge. This should be laid on top of the new leather which should have been slightly pared down before (on the skin side) or after (on the fleshy side) the old leather is put in place. If the cover is then pressed the result will be much more satisfactory.

If an old cover is placed on top of a new one the edges of the old one should be pared down only slightly and, once stuck, they should be bound using a thermoplastic adhesive or wax to prevent exfoliation and detachment. The adhesives most recommended for joining leather are flour paste treated with fungicides and, in some cases, polyvinyl acetate.

Decoration on bindings which has been lost (embossing and gilding) usually presents a problem of criteria to be followed. Throughout the history of restoration a wide variety of solutions have been adopted (among them the complete reconstruction of borders using photomechanical plates). The most widely accepted solution today is not to repeat the old decoration in the areas where it is missing but to leave it blank. In some cases, so as not to break the harmony of the whole, the main lines are continued on the inserts like embossed threads but they are not regilded.

With regard to cloth covers, if a rich material has been used, these present the restorer with considerable problems; it is often necessary to laminate them using crepoline or a synthetic material to restore their resistance and to conserve them as covers.

Mechanical cleaning by brushing, vacuuming or blowing air is recommended, the cloth being protected by a grille if its state of conservation is critical. Cleaning with water must be done with great care and only if it is absolutely essential. For this purpose, detergents, saponite or simply steam, are used. To avoid tears and deformation, the cloth is pinned to a surface and washed by gentle rubbing with a damp cloth. Should solvents be necessary, the most suitable is dichlorethylene, although any of the solvents mentioned in the section on paper restoration may be used (3.4.6) provided that they do not fade the cloth. Apart from the ease with which certain stains may be dissolved, the risk of deforming the cloth is less than if washed in water and the material dries more quickly. The most commonly used solvents for cleaning cloth in a bath are perchlorethylene and mineral turpentine whose action is enhanced for preference by an alcohol-based soap.

Drying the cloth is carried out by means of a blotter pressed down and fixed by means of pins.

There may also be metal ornaments on the covers, such as hasps and corner protectors. These should be cleaned using water and a detergent and finally treated with a lacquer and specific varnishes providing protection against dirt and oxidation (Paraloid or similar products).

Should it be necessary to reproduce any piece, this is done using brass. To give it an antique appearance which will make it harmonize with the whole, it is treated with a mixture of two parts nitric acid, one part hydrogen peroxide and one part water; after rapid immersion it is washed and heated in a flame. To avoid doubts concerning the authenticity of the piece the model should be simplified and the ageing process should not imitate exactly the "patina" of the original.


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