Volume 15, Number 3, Sept 1993, pp.34-36
Two books are reviewed in this column:
Although entitled Guide to the Maintenance of Outdoor Sculpture, this book does not describe how to do conservation maintenance in a traditional sense. Instead, this is a nontechnical book which tries to guide individuals who are responsible for the preservation of a collection of outdoor sculpture through the process of generating and implementing a written maintenance program. According to the authors, "the intent of this guide is to present a model for developing maintenance programs for outdoor sculpture," and "actual maintenance procedures for a specific sculpture or collection are not included."
The intended readership is broad-based and includes all the professionals who are identified as important players in the process: public art administrators, registrars, curators, museum directors, conservators, and others involved in the care of outdoor sculpture. While this book addresses the roles of all of these allied professionals, its target audience is private and public art administrators. These administrators are becoming increasingly involved with outdoor sculpture because of newly established "percent for art" programs and survey opportunities afforded through Save Outdoor Sculpture (SOS!). The book assumes that you have a collection but need to develop a strategy for collections care.
The authors suggest a three-step methodology for developing a maintenance program. The first two steps involve gathering information through an initial outdoor sculpture inventory followed by a more detailed sculpture-by-sculpture condition survey. (Unfortunately, examples of various inventory and survey forms, including the SOS! survey form, are not included in this publication.) The inventory and condition survey then serve as the basis for a comprehensive report that will determine the maintenance goals and priorities of a long-range maintenance plan.
The real strength of the book is the authors' discussion of the purposes and content of a long-range maintenance plan. They show how the long-range plan is multifaceted, and they not only clarify maintenance goals and priorities, but address administrative structure as well as fundraising and financial management strategies over time. Here the authors provide specific advice on what information should be included in the plan and what goals should be spelled out to best articulate the overall collections care policy.
With the long-range maintenance plan established, the next step is implementation. Here, the authors offer a few helpful hints, but remain fairly vague. Their emphasis on education of peripheral staff and the public is extremely beneficial, and they also touch on an important and controversial issue within the field--the training of conservation technicians. Although the authors issue a warning: "A little knowledge is a dangerous thing," they provide no real insights or answers to this difficult dilemma.
While the book ends with an excellent discussion of how to go about contracting conservation services, it is preceded by a weak section on materials used in outdoor sculpture. This section on materials may be useful to non-conservators, but conservators and other experienced professionals will find fault in too many generalizations and imprecise language that can be misinterpreted. For example, the authors discuss different air- abrasive materials in terms of weight, rather than hardness: "In some cases, heavier media (glass or plastic beads) may be appropriate."
The discussion of maintenance activities is problematic because the authors never differentiate between conservation treatment and maintenance. They do not mention that conservation treatments usually precede and often dictate maintenance activities. More importantly, the authors neglect to mention that not all of the "maintenance" activities that they describe are universally recommended, and that some--such as the consolidation or waterproofing of stone--involve toxic chemicals that present health and environmental safety problems. Here the authors might have been better off referring the reader to other publications and providing a more substantial bibliography. An unfortunate omission from the book was the AIC Code of Ethics & Standards of Practice, which the authors refer to many times.
The authors state that "the text of this guide is drawn from materials assembled for a symposium, "Maintenance of Outdoor Sculpture: Whose Job Is It?," held June 2-3, 1993, in Buffalo, New York, in conjunction with the 20th annual [AIC] meeting." Unlike other post-conference publications, this book is not a compilation of actual talks and handouts, but instead is a simplified and condensed version of the symposium in the authors' own words. The publication could have benefited from the different voices and opinions heard at the symposium. The case studies presented at the conference were not only informative, but helped focus on some of the real-life problems that administrators face when trying to implement a maintenance program. Nevertheless, the preservation of outdoor sculpture is a vast topic, and in Guide to the Maintenance of Outdoor Sculpture, the authors have tackled an important aspect of the process and have provided a valuable resource for developing a successful maintenance program.
(This review was first published in the United Kingdom Institute for Conservation's Conservation News, No. 51, July 1993, pp.19-20.)
John Morgan should be thanked for undertaking the admirable task of writing the first book devoted to the conservation of plastics. Similarly, The Conservation Unit of the Museums and Galleries Commission and the Plastics Historical Society should be applauded for realizing the need for such a book and organizing its production. However, while Morgan has written a good introduction to the history, manufacture, and deterioration of plastics, he is not a conservator and I do not believe that his treatment suggestions convey an understanding of conservation.
The stronger points of the book include the summary where he recommends maintaining low light levels, stable temperature and relative humidity, and adequate ventilation. He continues with brief sections on the nature and degradation of plastics and presents information on the composition and history of specific plastics in four groups: natural polymers, semi-synthetics, early synthetics, and post-war thermoplastics. There is also some information on manufacture and fabrication, a chronology based on availability, a short bibliography, and a list of historical acronyms.
Unfortunately, the weak aspects of the book are Morgan's suggestions for the treatment of plastics. In my view, the information is oversimplified for the complexity of the subject, and often contradictory and misleading. Even though caution is stressed, the suggestions for cleaning, washing, or coating are presented without prudent warnings highlighting the susceptibility to damage or long term impact.
Choosing materials and procedures suitable for repairing plastic is immensely difficult due to the extreme variety and chemical complexity. Since few conservators are plastic experts and fewer have the time or facilities to carry out extended scientific research projects, perhaps the wisest conservation advice (while others are researching) is to postpone treatment and attempt to slow the rate of deterioration by providing a favourable environment. While ventilation and emission absorbing materials such as activated charcoal may delay deterioration, determining the effectiveness of these measures requires knowledge of the composition of the material, the emissions and the causes of degradation, followed by thorough research and evaluation.
The same principles apply when cleaning or restoring plastic; first the major polymer and the additives must be identified, then thorough investigative research undertaken to determine materials suitable for use. Chemical dictionaries, product literature, polymer science publications and, increasingly, conservation literature contain useful information including lists of solvents that dissolve, swell, or cause stress-cracking of specific plastics. Some conservators also have information relating to the conservation of plastics. Sadly, I do not feel that Morgan's treatment suggestions indicate adequate consultation of these sources.
But my main criticism of the book relates to the treatment suggestions involving the use of solvents without clear warnings. To me, the most important advice when contemplating conserving plastic is that solvents should be avoided if possible, because incorrectly chosen solvents can do a great deal of damage very quickly. Solvents can dissolve the polymers in plastics as well as the additives, and also rearrange and extract components. In addition, solvents can damage plastics without dissolving them1. If absorbed, solvents can cause swelling, molecular chain scission, physical stress, and crazing or cracking. It is also important to note that damages resulting from solvent absorption may not be visually detectable1 a fact that invalidates Morgan's suggestion of simply testing a solvent in an inconspicuous area in hopes of determining the impact. Finally, as it is impossible to know the history and condition of a plastic artifact, it may be impossible to predict the impact of solvents. Unfortunately, cleaning solutions, adhesives, coatings, and polishes contain solvents. Not surprisingly, the three treatments that I found most alarming involved the use of solvents that could damage the plastic being discussed; these were water on cellulose derived plastics, ethanol and isopropanol on poly(methyl methacrylate), and lighter fluid or white spirit on unidentified rubbers and plastics. Water can have a devastating effect on cellulose derived plastics such as cellulose acetate and nitrate, and the suggested addition of ammonia or detergent can increase damage2. The alcohols, ethanol and isopropanol (propan-2-ol) are known to cause crazing or cracking of poly(methyl methacrylate) and should be avoided when cleaning3-5; and there are other considerations6. Lighter fluid (butane) and other aliphatic hydrocarbons such as white spirit, can damage some plastics and rubbers and accelerate degradation when absorbed1,6,7. An additional consideration is that some aliphatic hydrocarbon solutions contain aromatic hydrocarbons such as toluene, and these solvents generally damage a greater number of plastics.
For the reasons that I've explained, I also question Morgan's recommended list of solvents suitable for removing labels. Propan-2-ol is absorbed by many plastics as are the two aliphatic hydrocarbons listed. (Though it is difficult to suggest alternative solvents, I am inclined to consider using deionized water instead of an alcohol if the plastic is not casein or a cellulose derivative.) It seems worth mentioning that I have experimental evidence that three commercially available aliphatic hydrocarbon solutions of differing composition and volatility, as well as three alcohols, were absorbed in considerable amounts by samples of a commercially available natural rubber and a flexible polyvinyl chloride. These solvents caused considerable swelling and weight gain, and also extracted components1. (Longer term impact is presently being investigated after aging 5 years in the dark.)
My final criticism concerns Morgan's treatment suggestions that do not clearly state their experimental nature; specifically, annealing PMMA, applying oil coatings to plastics, and using polishes. First, even though annealing is used in manufacturing, it is not a suitable conservation procedure because there is too great a chance of damaging or accelerating deterioration of the plastic or any adhesives present. Second, the suggestion of coating cellulose nitrate with epoxidised soya bean oil is purely experimental; I could not recommend the use of any oil on plastics. Oils can be absorbed by plastics and the molecules can crosslink becoming more difficult, if not impossible, to remove. In addition, some oils darken with age, some degrade plastics and rubbers7, some contain solvents, and the solvents necessary to remove many oils can damage many plastics. Finally, I would not suggest using proprietary polishes on PMMA, and especially not on cellulose plastics, due to unknown impact of the unidentified components such as water and other solvents, detergents and aggregates; these components could cause damage or be left behind to unknown effect. The mechanical action of polishing may also introduce physical stress, making a plastic more susceptible to stress crazing in the presence of solvents. The use of polishes also raises the ethical question of removing the original surface. It is my view that the experimental nature of these treatments precludes application.
After so much criticism I should note that Morgan stated that he hoped his book would stimulate others to add their experience...until more authoritative recommendations emerge. I would like to thank him and take him up on this point by offering a few suggestions for future publications concerning the conservation of plastics.
First, there is a need for a publication covering identification techniques for plastics. It would be helpful if simple tests and scientific techniques were cited and evaluated for reliability and usefulness. Second, there is a need to compile information on preventive care for specific plastics. Guidelines for the use of dosimeters that identify and monitor harmful emissions, and information concerning the effectiveness of acid scavengers, such as activated charcoal, would be useful. Third, information concerning the impact of specific solvents on specific plastics is needed. The publication could be separated into groups by plastic with headings including those that are safe to use, those that are probably safe, and the ones that dissolve, swell, or cause stress-crazing or cracking. It would be very useful if the solvents listed were grouped by chemical family and solubility parameters were given. Data from existing conservation related studies would also be beneficial. This information would enhance the understanding of the effects of solvents on plastics and narrow the range of solvents that may be suitable for cleaning, coating or repairing plastics, and ultimately, provide a good foundation for future studies relating to the conservation of plastics.
1. Sale, D. "The Effect of Solvents on Four Plastics Found in Museum Collections: A Treatment Dilemma" in Modern Organic Materials, Scottish Society for Conservation & Restoration, Edinburgh, (1988) pp 105-114.
2. Blank, S. "Review of Conservation of Plastics" in Studies in Conservation, vol 37, (1992), pp 278-286.
3. Brydson, J.A., Plastics Materials, 4th ed., (London: Butterworths Scientific, London, 1982). p 372.
4. Imperial Chemical Industries PLC, Perspex Cell-Cast Acrylic Sheet: Properties and Fabrication Techniques, PX 127, 4th ed., ICI, Darwen, Lancashire, (1989).
5. Rohm GMBH, Chemical Resistance in General Use: Plexiglas GS and Plexiglas XT, (Rohm GMBH Chemische Fabrik, Postfach 4242, Darmstadt 1: Rohm Plastics, 1986)
6. Sale, D. "An Evaluation of Eleven Adhesives for Repairing Poly(methyl methacrylate) Objects and Sculpture" in Saving the Twentieth Century: The Conservation of Modern Materials, Proceedings of the Conference, 1991, Canadian Conservation Institute, Communication Canada, Ottawa, (1993) pp 325-339.
7. Blank, S., "Rubber in Museums: A Conservation Problem" Australian Institute for the Conservation of Cultural Material, Inc., vol 14 (December 1988) pp 53-94. u
Don Sale, Assistant Keeper
Sainsbury Centre for Visual Arts
University of East Anglia
Norwich, Norfolk NR4 7TJ England