CERAMIC RESTORATION AND CONSERVATION,
A QUESTION OF VALUES
Pottery is of course one of the longest-lived handicrafts. Its manufacture, whether utilitarian, architectural, or decorative has always moved in parallel with general artistic movements, and therefore, serves as a fair reflection of any era. Often the only surviving artifacts of earlier civilizations, ceramics are perhaps singularly the most important remnant to the archaeologist for dating, interpretation of technology, trade routes, religion and the simple reflection of daily routine. These interpretations could well be applied to ancient Mesopotamia, or colonial Williamsburg, as relics survive in abundance. Ceramics are generally durable and stable, yet we find the need to intervene for a number of reasons; chemical analysis for dating, reconstruction of shards for simple display, stabilization of surfaces or environment to prevent deterioration, and fabrication of missing elements to enhance value or to conceal damages. It is these latter areas which are the concern of the conservator and the restorer.
Since the bulk of ceramics made over a 10,000 year period are soft bodied in nature, early attempts at restoring broken objects involved various plant juices such as garlic and mulberry, tree saps and gums. Insect resins such as shellac proved a versatile adhesive and coating with numerous applications. Fish and hide glues have also enjoyed popular usage. There are references in sixteenth century Chinese manuscripts giving recipes for adhesives for the repair of porcelain, which is a more problematic application due to its vitreous nature. Egg whites and glutinous rice, wheat gluten and lime, bamboo resin and egg whites are but a few of the suggested remedies. A standard work on household management published in England in 1861 gives recipes using brandy, gum mastic and isinglass.2 Earnest Spon’s Workshop Receipts of the same period advised boiled Gloucester cheese combined with quicklime or orange shellac and rectified spirit for rebonding ceramics.3
In other cases mechanical repairs have been used to bind broken pieces, and in some instances return a degree of function. One the earliest repairs of which I am aware involves a large storage jar from Palestine, around 5000BC, where holes either side of the break were drilled and a leather strap laced through to bind the fracture. It was a simple utilitarian vessel, obviously important to someone at the time as considerable effort went into its preservation, thus avoiding the purchase of a replacement. From dynastic Egypt we find relics on which may be seen cannibalized repairs. This is where a missing section, say the legs, head or an arm is replaced from a like object to return the prestige or spirit to the figure. We find the same techniques used on eighteenth century Chinese and European figures. In more recent centuries where utilitarian objects have doubled as objects of both function and beauty, repairs serve the duel purpose of returning use and preserving aesthetic qualities. In these cases the repair takes on a complimentary role and becomes part of the pieces appeal; silver tea spouts and covers, pewter handles or ormolu mount hiding a damaged base are but a few examples.
The most widely used methods of mending ceramics in the last four hundred years are metal riveting, lacing and doweling. Riveting has its origins in China and found wide usage throughout Europe and the United States up to the middle part of this century. The technique was developed and used primarily on porcelain because there were no lasting adhesives available to bond such vitreous material until the formulation of epoxies and polyester resins. Metal clamp repair required considerable skill, as is obvious in the diversity of results. Even in the best cases, the process is destructive and unsightly. Holes were drilled either side of the break, and the rivet, usually brass or iron, was cut and then pulled into place.4 These were usually situated on the backside of an object, and perhaps hidden within decorated areas to lessen the visual impact. Unfortunately rivets often corrode and stain, breaklines also become soiled. Over time these antiquated repairs may become unstable and require re-restoration. In these cases the restorer/conservator is faced with twofold damages, those of the original breakage and those of the riveter, nonetheless it was the only solution available for its time. One positive characteristics of their use is the return of function. They were not likely to weaken by exposure to hot and cold water, detergents or grease, as would be the case when using an adhesive. It is for this reason that any modern restoration or conservation treatment should not be considered functional.
A rather curious procedure came along in the latter half of the eighteenth century called "china burning". A broken vessel was rejoined by applying a highly fluxed glaze or enamel to the break edges, then refired. In our observations the breaks were neither cleaned nor properly aligned prior to joining. . The most bizarre aspect of this practice is that the china burner often signs the "mended" article. This process is irreversible.
Although as a profession we like to feel that restoration and conservation has come of age in the past thirty years in terms of ethical methods and materials, we find a strong undercurrent of bad information and application. Popular courses on ceramic restoration such as the "Klein Method" and texts such as How to Mend Your Treasures, Porcelain-(China)-Pottery and Glass are available at many local libraries and have served as a means of self instruction.5 Many practitioners have perpetuated a practice built around the use of grinders, dental drills and irreversible materials and techniques.
The means for ethical repair have existed for many decades. The problem lies in the lack of training grounds and organizations to disseminate information about advances in materials and techniques. Suitability must extend to each phase of restoration or conservation; appraisal of material and condition, cleaning, stabilization, bonding, remodeling and retouching. There must be proven tests and results for the likelihood of discoloration, shrinkage, long term stability and most important of all, the quality of reversibility. This principle is the benchmark of modern conservation and restoration practice. All ethical treatments are designed to have as little impact on the original material as possible both in application and in removal. We defer to the conservation materials scientist in these matters and then with caution. There are a number of materials whose use was widely accepted in the last thirty years which, contrary to artificial aging tests, proved to have adverse effects on the ceramic within a few short years. It is presumptuous to think that a certain method or material will last much longer than the conservator or the restorer who implements it. We are looking for materials with years of testing and hopefully decades of use. They are few and consequently we are becoming minimalists, erring on the side of doing as little a s possible to stabilize deterioration and compensate for damages. Unfortunately we are looking at time frames of ten to twenty and perhaps thirty years as acceptable parameters of aging characteristics for many materials. Commercial products used for bonding, casting, filling or retouching are manufactured with an eye to multi-purpose applications. There is little attention given to long term aging properties. The conservation/restoration materials market is so small that it rarely justifies the research and development needed to fulfill our narrow requirements. In addition, the manufacturers are loath to reveal commercial formulations so that researchers can determine their suitability for our use. This is an interesting difference between glass and ceramic restoration and other fields such as textiles, furniture and paintings. These areas, though rife with problems of natural deterioration, can often allow the use of original techniques and materials to compensate damages. Our one common approach is the proper choice of display and storage to extend the life span of the object and the repair.
One point of confusion that still may exist in the public’s mind is the difference between conservation and restoration. Conservation refers to the processes, which keep an object from harm, loss or future decay and simultaneously preserves the true nature of the object. "True nature" could be interpreted as evidence of origin (anything indicative of the making or process like firing faults or craze lines), associated materials which illustrate use (contents of a funerary urn or apothecary jar), or even subsequent historic modifications which are significant enough to preserve (engraved silver rivets or tea spouts, Japanese gold lacquer repair or ormolu mounts masking breaks). This ethic and practice we call art conservation is relatively new to the scene, having evolved from the more shadowy realm of art restoration. With roots in the 1930’s, the idea rose with newfound scientific objectivity and methodology in the desire to protect and prolong art works that were at risk. The use of microscopes and x-rays furthered the field of study and application.6 Today the practice incorporates interdisciplinary studies in art history, studio art, chemistry and archaeology. The trend is toward specialization in specific areas of art objects and artifacts. Collections management, disaster planning, environmental assessment, dating and analysis, storage and exhibition design are becoming part of many conservators repertoire of skills. Restoration, on the other hand, is aimed at bringing an object back to an approximation of its original state through the concealment of damages. The term restoration has taken on a rather derogatory image mainly because of associations with deception, fakery, and destructive alteration having little regard to original style or compostion.7 Many of these alterations were considered practical and permissible in their day. It is our current standard, which demands authenticity and a more considered approach to repairs.
A restoration can be both desirable and honest if carried out to a discreet level where all original surfaces are visible. Fillers and paints would be applied within the confines of missing areas only. There would be no attempts to disguise inherent damages such as glaze faults, kiln damages or slumping. There can be no improvement on the original intent or fate of process.
In order to best reveal true nature and original surfaces, it would stand to reason that a lot of emphasis would be placed on cleaning. Often times overspray restoration through the use of an airbrush is carried out to mask stains, haircracks and simple breaklines. Advances in the use of various detergents, solvents, mild acids and alkalis, steam wands, and poultices (and soon lasers!) has given us the ability to either totally remove the stains or at the least lighten them considerably. This attention to cleaning processes often precludes the need for further, more invasive and costly repairs. Adhesives, particularly for use on porcelain, have always been a problem due to their yellowing and viscosity. There have been considerable advances in the use of epoxy resins for bonding and more importantly for matching "color fills". When properly manipulated and applied these materials give the restorer the ability to mimic depth, translucence and color when filling voids, glaze loss, rivet holes and chips specific to the areas of damage without obscuring original surfaces. It can also be used to imitate parian, jade and cloisonné. We are hopeful that under the right conditions of after care we will see these applications lasting decades rather than years.
Traditional methods of restoration using the airbrush and various lacquers and paints to obscure breaks and fillers are going to last less than ten years before obvious discoloration sets in. Feathered paint surfaces around damaged areas are applied so thinly as to risk abrasion even in the course of normal handling. One thing you can say for the technique is that when well executed the results are very convincing from a normal viewing distance, ( but the question must be asked, "convincing of what?"). This method has its place in certain instances, but it is as far as you can get from original surfaces and the true nature of the piece. The most disturbing aspect of this technique is the potential for deception. Once yellowing takes place (and all synthetics will discolor against the inert original ceramic) and the repair becomes more obvious you are faced with the dilemma of condition. Because of the broad expanse of overspray, there is the question of what lies beneath the paint. It may be as simple a defect as a dirty haircrack, or it may be large missing areas replicated in plaster or resin. Under ultra violet light the area of overspray may be revealed unless of course the entire piece has been oversprayed in which case the object will fluoresce the same throughout. As a buyer or as an appraiser you are then in the unenviable position of attempting to determine value. Fortunately this coating is reversible and can be removed to reveal the true condition, for better or worst. What is often found is an abraded surface. Earlier mention was made of techniques established by the "Klein Method". The accompanying text to this course of instruction suggests grinding off poorly bonded joints or creating a "V" groove along all break lines to accept fills and then covering the tracks with the airbrush.8 In addition we often find the missing areas, which had been remodeled, cast or filled, have been "rubbed down" with abrasive papers that are much stronger than the glaze or enamel decoration itself. Aluminum oxide, silicon carbide and flint sandpaper are often used by restorers to pare down the fill, and in the process the surrounding original glaze, enamel and gilt decoration are scratched away. Abrasive papers composed of ground glass, a material softer than most glazes and enamels are widely available in Europe but have not found their way onto the U.S. market until quite recently. The clever finished appearances of restoration do not mean a thing in this field as a mark of credible ethical repair!
It is fair to point out though that large missing areas cannot always be compensated with colored fillers and be acceptably discreet. If standard practices have been employed, if all materials remain reversible, if damages are not incurred, and documentation exists as to how a repair was done and to what extent, then arguments can be made for the use of an airbrush and overpaint. If documentation provided by the conservator or restorer is not passed along with the object then, despite our best efforts, we are back to square one. With museum objects documentation is dutifully placed into the file as part of the object’s history. If the piece goes into the marketplace however, this important information is considered a hindrance and is often discarded or reduced to a simple "restored" on the label.
Without wishing to overstate the point, the pressures of the market and the lack of, but desire for well-conditioned objects, have placed much of our cultural heritage at risk. There is considerable work to be done to raise consciousness. Most of this challenge lies in the conservators’ and restorers’ arena yet there will always be more art works and artifacts in need of treatment than there are qualified persons to meet that need. While 'how to" texts and the ever popular one week course may provide a starting point into the field of restoration it should not be considered a qualification or a certification of professional practice. Regardless of our backgrounds or our training we all have an obligation to honest stewardship of the objects entrusted to us.
The Conservation Analytical Lab at the Smithsonian, the Getty Museum and the British Museum and a handful of university conservation programs are all actively involved in developing and testing new methods and materials for ceramics and glass. Among institutional and private restorers and conservators there is a movement to standardize the practice, to make known these few acceptable, tested procedures and to establish uniform ethical standards in dealing with both material and client. The United Kingdom Institute of Conservation, Ceramics and Glass Section (UKIC) has taken a lead since 1984 in establishing professional guidelines and innovative refresher courses. The International Council of Museums (ICOM) has recently created the first international ceramics and glass conservation section.
There are a number of organizations, which deal exclusively with art conservation and restoration issues. As memberships cover an extraordinary range of disciplines and specialties, they serve as excellent sources of information for inquiring institution or individuals.
The American Institute for Conservation of Historical and Artistic Works (AIC) is the national organization for professional conservators and interested co-disciplines. They can provide information on how to select a conservator, lists of various training programs in the U.S. and abroad and a membership listing giving geographic and specialty breakdown. The AIC cannot recommend individual conservators. While the AIC is the major professional body for conservators in the US and does set forth a stringent "Code of Ethics and Standards of Practice" for member conservators, the organization does not certify professional competence.
The National Institute for the Conservation of Cultural Property (NIC) publishes various reports on conservation issues. These publications provide good general information of interest to both conservator and non-conservator.
The International Institute for Conservation of Historic and Artistic Works (IIC), the international Council of Museums: Committee for Conservation (ICOM) and the International Centre for the Study of the Preservation and the Restoration of Cultural Property (ICCROM) are a few of the international organizations dedicated to conservation. They all publish journals and periodic papers of specific and general interest.
In addition there are a number of regional conservation organizations and Cooperative Conservation Centers, which may be able to provide listings of private conservators within specific regional areas.
The following points as stated in the very useful AIC/FAIC brochure on "Guidelines for Selecting a Conservator" provide the minimal considerations for selecting a conservator:
- Learn about the field of conservation.
- Ask for advice and recommendations from other conservators and museum personnel when looking for a qualified conservator.
- Contact conservators’ previous clients.
- Investigate references.
- Avoid basing choices on convenience or rushing into a contract.
- Request information about the selected conservator’s background, training and professional affiliations.
- Expect to receive from a professional conservator the following:
a) a written preliminary examination evaluating condition, proposing
treatment, describing limitations of the treatment, and providing estimates
of treatment costs and duration.
b) notification during treatment of major changes in the proposal.
c) written and photographic documentation of the treatment, and when
appropriate, recommendations for continued care and maintenance.
Notes
1. Nigel Williams, Porcelain Repair and Restoration (London, U.K., British Museum
Publications Ltd., 1983, p.11.
2. lbid., p. 12.
3 lbid., p12
4. C.S.M. Parsons and F.H. Curl, China Mending and Restoration (London, U.K.: Faber
and Faber Ltd., 1963).
5. Laurence Adams Malone, How to Mend Your Treasures Porcelain-(China) Glass-
Pottery (New York, New York: Phaedra Inc., 1972), p. 42-43.
6. Peter E. Michaels, "Accreditation, Certification and Licensing of Art Conservators",
Preservation and Conservation: Principles and Practices (Washington, D.C.: The
Preservation Press, National Trust for historic Preservation, 1976), p. 436.
7. Caroline K. Keck, "The Role of the Conservator", Preservation and Conservation:
Principles and Practices (Washington, D.C.: The Preservation Press, National Trust
for Historic Preservation, 1976), p. 26-27.
8 Klein, William Karl , Repairing and Restoring China and Glass. The Klein Method., Harper and Row, 1962.
Information Sources
The American Institute for Conservation of Historic and Artistic Works (AIC)
1717 K Street, NW, Suite 301
Washington, D.C. 20006
National Institute for the Conservation of Cultural Property
The Papermill, Suite 202
3299 K Street, NW
Washington, D.C. 20007
International Institute for Conservation of Historic and Artistic Works (IIC)
6 Buckingham Street
London WC2N 6BA, England
The International Council of Museums (ICOMUS)
Committee for Conservation Maison de I’Unesco
1 rue Miolis Paris XVe, France
The International Centre for the Study of the Preservation and the Restoration of
Cultural Property (ICCROM)
13 Via di San Michele
00153 Rome, Italy
The United Kingdom Institute for Conservation of Historic and Artistic Works (UKIC, Ceramics & Glass Group), 109 The Chandlery, 50 Westminster Bridge Rd., London SE1 7QY
Selected Bibliography
Buys, Susan and Oakley, Victoria, Conservation and Restoration of Ceramics, Butterworth-Heinemann, UK, 1993.
Cushion, John, An Illustrated Dictionary of Ceramics, Thames and Hudson Ltd., London,
U.K., 1985.
Guildbeck, Per E., The Care of Historical Collections: A Conservation Handbook for the
Nonspecialist, American Association for State and Local History, Nashville, TN.,
1972.
Hodges, H.W.M., "Problems and Ethics in the Restoration of Pottery", Stockholm
Conference on Conservation in Archeology and the Applied Arts (I.I.C., London,
1975).
Larney, J., Restoring Ceramics, Barrie and Jenkins, London, U.K. 1975
Newton, Roy and Davison, Sandra, Conservation of Glass, Butterworth-Heinemann, 1989.
Plenderleith, H., and Werner, A.E., The Conservation of Antiquities and Works of Art,
2nd edition, Oxford University Press, 1972.
Plowden, A. and Halahan, F., Looking After Antiques, Pan Books, Ltd., London, U.K.,
1987
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