Leonardo

Restoration Technology for Contemporary PaintingsAuthor(s): Robert E. FieuxSource: Leonardo, Vol. 15, No. 4 (Autumn, 1982), pp. 283-286Published by: The MIT PressStable URL: http://www.jstor.org/stable/1574736 .

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Leonardo, Vol. 15, No. 4, pp. 283-286, 1982 Printed in Great Britain

0024-094X/82/040283-04$03.00/0 Pergamon Press Ltd.

RESTORATION TECHNOLOGY FOR CONTEMPORARY PAINTINGS

Robert E. Fieux*

Abstract - Many contemporary paintings have been considered unrestorable. Concern over the situation has focused mainly on the methods and materials of artists. This article draws attention to the responsibility of restorers to maintain a technological parity with artists. The present state of the art is briefly examined, and certain technological advances in restoration are described, outlining their advantages and benefits to contemporary paintings.

A question that has been asked with increasing frequency about contemporary paintings is, 'Can they be restored?'. It tends to imply that restorability is mainly the responsibility of the artist, who chooses the materials and techniques to be used. All paintings deteriorate with age, regardless of the greatest concern for permanence. Without periodic cleaning, reinforcing, and repair, all pictures would become decrepit in appearance and in condition. But, aging is not alone responsible for attrition of paintings. Many have been damaged or destroyed by restoration processes, some of which are still in use today. It may be appropriate to look at the state of the art, and to learn why present restoration methods are often inapplicable to con- temporary pictures.

From the point of view of restoration, paintings have two separate qualities setting them apart from all other artistic objects, both of which become a major focus of preservation. The first is the painting as a mere object, and the second is the unique image which the artist creates through the combination of materials being used. Paintings are heterogenous and amorphous constructions. The complex and varied materials they contain all combine into a single object, yet each material retains its individual properties. The artistic surface of color, form and texture presents a highly individualistic appearance in each one. The job of restoration is to preserve not only the object itself, but also its unique appearance.

Because of the physical nature of paintings, particularly those on canvas, in which each of the component materials retains its individual physical properties, a procedure intended to correct a defect in one of the materials can be detrimental to another. What makes any restoration difficult, particularly for many contemporary paintings, is that restoration materials, especially adhesives, require bonding techniques that can be seriously damaging to the aesthetic qualities of a painting, even though they may preserve it as an object. The visual qualities of color, form and texture are the main aesthetic features of many contemporary paintings, and are the most vulnerable to traditional restoration processes.

The revolutionary aspect of contemporary painting styles includes a departure both from recognizable images and from traditional methods and materials that artists used (Fig. 1). The development of oil painting techniques on canvas supports had not changed much since the 17th century, except that commercial manufacturers relieved artists of the task of preparing materials. Because the initial life span of a painting is about 75-100 years before aging compels some kind of intervention to prevent its loss, the periods marking the evolution of restoration methods lag somewhat behind. The

*Conservator, Fieux Restoration Laboratory, Inc., 263 Cedar Street, West Barnstable, MA 02668, U.S.A. (Received 23 Nov. 1981.)

record indicates that by the 18th century the practice of lining had begun and by the 19th century it was the general manner of preserving paintings. This chronology coincides with the approximate 100-year lag after the introduction of commercially primed canvas in the early 1700s, which incorporated a thinned glue sizing, forcing a change to the restoration techniques that are in use today. The historical lag of about 100 years between changes in artist method and a compensating move by restorers, determined by the aging of paintings, has held largely true until artists departed from conventional painting materials. Many of the new materials are now seen to have a shorter life, necessitating earlier treatment.

If artists held closely to tradition, they did accept the outside source of commercial art materials. Restorers, however, were never so lucky as to find ready-made supplies. They have always relied upon their own resources to prepare their needs themselves. The atmosphere created by individuals mixing things up in the privacy of their own workshops, combined with the competitive nature of the market place, led to a certain secrecy in which each restorer reserved to himself the 'secrets of the trade'. Spreading of information and knowledge came about as apprentices and assistants went abroad to establish their own studios. In this way the development of restoration reached the middle of the 20th century, considered and practiced more as an art than a science.

The last 30 years has been a period during which restorers

Fig. 1. 'Flat Black'. Monochromatic collage, 30 x 40 cm. A work ofthis type cannot be cleaned or lined by traditional restoration methods, and is among

those which would be classed as unrestorable.

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Robert E. Fieux

have recognized the need to become more free in sharing knowledge, and to seek channels of communication with branches of science and industry having parallel interests. A number of improvements in materials were introduced during this time as the result of a general acknowledgement of the inadequacies of traditional restoration processes. Those improvements, however, were intended for the treatment of traditional style paintings. In the meantime, virtually unnoticed, the aging period of contemporary paintings has grown alarmingly shorter and shorter.

There is another phenomenon in the history of restoration practice that seems to have occurred in recent times. The adoption of acrylic synthetics for varnishes, adhesives, and other art uses came approximately 20 years after the large-scale introduction of these synthetics by industry. Acrylic develop- ment of the 1930s became the new art materials of the 50s and 60s. The 20 years leading into the 1980s has brought an enormous increase in research and development by industry, providing innumerable products of high-technology calibre that themselves have become the basis for entire new industries. Many of these new materials could become valuable in painting restoration because of their greater stability, and because many of them have properties which can enlarge the present repertory of methods by providing many more options.

For example, many lining methods of the present rely upon thermo-pressure techniques. The idea behind lining-of putting a new material on the back of deteriorating paintings-is perfectly sound. A good backing support relieves the original canvas of all stresses, and holds it flat. Among those tried have been wooden panels, canvas, and, more recently, pressed-wood panels and aluminum sheets. Each one has its advantages, but also each has its drawbacks. Then, too, it requires an adhesive of some kind to secure the two together. Experience over the years has shown that solid mountings are inadvisable because wood splits and warps, and in large sizes is very heavy. Pressed-wood or aluminum have not as yet gone through the test of a full period up to the point of replacement, but it is not considered good practice to place paintings on a mounting that can be difficult to remove in the future. Hence these remain doubtful. Among all of these, canvas linings have been the support by far the most often used. Even though it also degrades, this can be an advantage over solid mountings, because the old lining can easily be peeled off and replaced. The adhesive used must therefore be a kind that can readily be released from the back of the painting.

Adhesive technology remained quite simple until the second quarter of this century. By 1945 there were over 200,000 new adhesive compounds, with more being developed at an accelerating rate. Among all of these evidently few attracted the attention of restorers. A wax-resin mixture, introduced in the 1850s, remains the standard for lining a century later. This slow rate of acceptance was somewhat accelerated by the use of a vacuum hot table, introduced in the 1950s, a device which simplified the task of maintaining uniform heat and pressure over the entire expanse of a painting which was being lined with wax-resin. However, the thermoplastic nature of the adhesives now used for lining actually is one of the chief obstacles in the restoration of contemporary works.

From the earliest times adhesives have been both the life and the death of paintings, when saturating a painting with glue was the custom. Attaching a lining came later, together with a need to apply holding pressure to keep lining and painting in contact until the glue became dry. The flattening action of pressure on a distorted painting also was considered a desirable secondary result, and has been retained as a standard function of lining technique. The bonding process being done under heat and pressure is required not only by wax-resin formulations but also by alt of the synthetic resin lining adhesives in use today. An important feature of adhesive characteristics is the method of

application. In the case of lining adhesives, wax-resin must be applied in the liquid state as a molten material, and it must be kept that way to be uniformly spread over a surface, and also when the joining occurs. Molten wax flows and penetrates completely through a painting. If there is light colored, absorptive material present in the artistic pattern, wax will stain it dark, like a grease spot. New synthetic resins are now used as adhesives in ways that avoid penetration into absorbent materials. However, these new thermoplastic adhesives such as Beva 371, or polyvinyl acetate (PVA), still require heat and pressure to achieve the bonding of lining to painting.

The major obstacle confronting restorers in lining contem- porary works is this requirement of heat and pressure when using thermoplastic adhesives. The preservation of paintings as objects which can be hung on a wall and exhibited is totally dependent upon the ability of restorers to provide a satisfactory lining without damaging the picture. Because there has been only the one option of thermo-pressure lining available to them, a large number of contemporary works that would be damaged if placed under heat and pressure lie beyond their reach as long as restorers are confined to using thermoplastic adhesives.

Adhesive technology, meanwhile, continued with the development by industry of thousands of highly specialized adhesives, many of which were tailor-made for a specific need. Among the most recent group of chemical compounds from which a large number of adhesives have been made are the silicones. As a basic compound, silicone has one of the most desirable properties of all synthetic materials for restoration uses: stability. It forms the new generation of broad-spectrum synthetics from which a wide range of durable materials can be made, having very specific properties to fill certain needs.

Adhesives are classified according to their basic formulation, method of application, bonding technique, and performance ability. On the other hand, adhesive requirements are determined by the type of material to be bonded, the stresses the adhesive will have to support, the durability requirements, and any other special factors that can affect the bonding technique. An adhesive should be selected that will best suit all of the requirements of the job. Also, there are certain factors that rule out the use of particular adhesives. In restoration an adhesive is unacceptable if it distorts or imparts distortion to a painting, or if it becomes so hard and intractable that it cannot be removed later on. For many contemporary paintings there are further restraints. An adhesive must not be penetrating or staining, and it should not require pressure during bonding. It is possible today to select from among a wide number of adhesives that might be suitable as a class, choosing one that most specifically satisfies the needs of paintings.

Glue and wax are the traditional lining adhesives. Glue is an animal product and is classified as an organic, protein-based adhesive. It must be applied and bonded while in the liquid state, or while there is sufficient water present to reactivate it with heat while bonding. In all cases glue requires pressure during bonding. Wax is a thermoplastic, but it differs from synthetic thermoplastic adhesives in that it must be applied and bonded in a molten state. To achieve a bond with wax, both the work and the wax must remain hot enough, about 65?C, to keep the wax molten, the heat must be applied under pressure during bonding, and the wax must then be cooled while still under pressure. Wax or glue are the main adhesives used in the lining of paintings.

The reason why standard restoration methods are inappli- cable to many contemporary paintings becomes clear on just two counts. Liquid adhesives penetrate entirely through a canvas and will stain. Heat and pressure will damage or destroy textural features that are soft or crushable. (Fig. 2). If the properties of a majority of all paintings are compared they will be found to be vulnerable to heat, pressure and water.

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Restoration Technology for Contemporary Paintings 285

Silicone adhesives are classified as inorganic, and can be formulated to meet a variety of specifications. Among them is a type of adhesive that is familiarly found in several types of general purpose tape that is just pressed on. They are known as pressure-sensitive adhesives. Adhesives of this type can be prepared by a manufacturer in advance by putting them on a convenient substrate. The adhesive becomes dry, but remains sticky to the touch, and is supplied in this way for use by simple finger pressure upon a surface. These PSAs (pressure-sensitive adhesives) do not require heat or significant mechanical pressure, they are applied in a dry state and are therefore non- staining. Among the group of adhesives based upon inorganic silicon there are various PSAs which have much greater stability than previous ones and which can be fully processed by the manufacturer on a substrate on which it can later be supplied. This most recent technological development by industry promises to be one of the most important advances for restoration techniques, and especially for contemporary paintings.

Experimentation with silicone adhesives for lining use during the 1970s required that improvements would also have to be made in the kind of material used as the lining fabric. The silicone PSA could not be applied to canvas, which actually became the weakest technological link in the new chain. The importance of properties of materials at an interface is well demonstrated in the instance of an adhesive-lining fabric combination for a painting, involving a PSA.

The functioning of the adhesive and that of the lining differ with respect to the type of support they provide: the lining process itself is simply attaching the lining to the painting. Traditional lining methods that employ penetrating adhesives with heat and pressure combine the flattening function as a non- essential element to bond on a lining. Because there were never other alternatives, the thermo-pressure function is still considered to be a valid part of a bonding operation. The possibilities of a PSA adhesive on a proper lining substrate, in which a lining can be applied to a painting without recourse to heat or pressure, changes the entire prospect for the restoration of almost all contemporary paintings. The work of the adhesive is to provide a bond to the lining that will securely hold the painting in place. The lining, on the other hand, must be strong enough to support the entire weight of itself and the painting, and preferably be neutral to temperature and humidity in the environment. Canvas is not the most efficient in this regard, and its life-span of hardly 100 years means that paintings lined on canvas must be repeatedly relined, which has had a damaging influence on paintings in the past.

A fabric that had been tested as a replacement for canvas lining, fiberglass, is too unstable dimensionally for ordinary purposes. But when it is unified with a coating it becomes very strong. Most coated fiberglass, however, is found as a structurally reinforced fabric in a heavy, unwieldy form. But a very new technique in coating has made possible the fabrication of a Teflon (DuPont TM) coating cured directly on the glass fabric. When the Teflon coating is kept to a minimum, the resulting product is a strong, neutral, durable, and porous glass fabric, in which both components are inert. This newly developed cloth can then have a silicone PSA applied and cured, resulting in a single product (Fig. 3). The porosity of the fabric complements the reversibility of the silicone PSA which can be released by the solvent, V. M. & P. naphtha, when applied from the back.

The basic concept of how paintings can be lined is dramatically changed through a combination of new materials that previously never existed, presenting opportunities for the successful preservation by lining of a wide variety of

Fig. 2. (Top) Detail of a badly distorted painting. A heavy paint layer of irregular thickness often causes this kind of deformation. Because the paint was soft and absorbent, damage to textures and to colors could have occurred if traditional lining methods had been used. The system developed by the author was employed to flatten and line the painting. (Bottom) The

same painting after restoration.

Fig. 3. To line apainting, apiece ofFabri-Sil(John G. Shelley Co., Wellesley Hills, Mass., U.S.A.) is cut from the roll in the desired size. When the protective cover is peeled off, the silicone PSA is exposed, ready to receive the flat painting. None of the traditional thermo-pressure equipment is

necessary.

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contemporary works of art. The reciprocal properties of the right technological materials in combination becomes the key to an enlarged restoration capability. Although not specifically produced individually for the purpose, materials chosen for their particular performance and supplemented by others similarly chosen can produce another material that becomes easy to use in what formerly were very difficult lining problems.

The flattening function of pressure-lining methods auto- matically became ruled out for use on crushable surfaces and those with soft or extreme textures. However, flattening still remains, as a required treatment, because many of these same paintings have become distorted through their weight or from interaction among the materials the artist used. Pressure from above cannot correct linear changes that have created sags in the original geometric shape of a canvas and in any case was never the proper treatment for any painting. A canvas is a planar construction that can be thought of as a sail. If it is held by its .edges and pulled, it will return to its original shape, and become flat. This principle is the mechanically correct way of flattening a planar figure, especially one with a delicate, sensitive surface. Paintings that are fastened in an expandable frame, again relying upon the use of special adhesives, can slowly be drawn back into their former shape, dimensions, and flatness. The surface need not be touched at all (Fig. 4).

In actual practice, paintings that require flattening are first mounted in a frame and completely returned to the desired attitude. Lining on new material, called Fabri-Sil (John G. Shelley Co., Wellesley Hills, Mass., U.S.A.), then follows by putting the painting on the Fabri-Sil and smoothing it out by hand. There are many paintings that do not need to be flattened, and these can simply be lined on Fabri-Sil directly without any other preliminary treatment. This new lining technique has been used successfully on such difficult and varied works as those by de Kooning, Kline and Rembrandt. But, in addition, it has been used for collages, absorbant pastels, and many others. Variations of the same type of materials have been made in panel form for those works requiring a solid mounting.

The preservation of contemporary paintings depends upon the ability of restorers using suitable materials and methods, just as much as the continuing existence of all paintings of the past still do. The major obstacle until now in the treatment of contemporary works has been the incompatibility of old restoration methods with the new materials artists now use. It has been shown that the most basic restoration treatment, lining, can be used to help preserve many paintings that previously could not be lined. There are tens of thousands of these works now in existence that are highly valued. The artists, and those who appreciate their works, should know that they can be preserved.

Research and development in restoration technology as it

Fig. 4. Textural surfaces of paintings remain untouched when thermo- pressure methods are avoided Paintings, as seen here, are mounted at the edges into a strainer frame, and drawn flat. The internal static field of the electrostatic lining table (Lectroplaque Lining Table, John G. Shelley Co., Wellesley Hills, Mass., U.S.A.) attracts a painting against its surface, assisting in the process offlattening. Very large andheavy paintings can be

processed in this manner.

applies to paintings has not stopped with lining. There are now available to restorers new solvents, cleaners and techniques that enable many of these same works to be safely cleaned. Lastly, a new varnish, Varni-Sil (John G. Shelley Co., Wellesley Hills, Mass., U.S.A.), which also has a silicone base, has been made available to restorers, and to artists. With superior stability to resist chemical change, this varnish was designed for the long- term care of paintings. It can be removed from a painting for future cleaning with a fluoro-solvent, and permits the preservation of even the most delicate work without harm.

Industrial technology is the only source for materials that will enable restorers to meet the new needs for restoring contemporary paintings. Specific materials intended for their restoration do not exist. Restorers as a group will have to settle upon the means to gather the products of industry together, and to form a new technology of their own. That is how all technologies are created. At the present time some basic materials have been made available from the most advanced sources in existence today. They are products that are now available to restorers. But industrial technology does not stand still, and the future will certainly bring with it a continuing flow of materials that can help restorers meet their needs.

286 Robert E. Fieux

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