ASPECTS OF CHEMICAL RESEARCH IN CONSERVATION: THE DETERIORATION PROCESS
ROBERT L. FELLER
2 VARIOUS RESEARCH OBJECTIVES
Some papers that one may encounter in journals and symposia represent an effort to transfer into conservation practice techniques already well-developed in other fields. In the presentations that follow, Walter McCrone's (1994) discussion of the use of polarized light microscopy or Chandra Reedy's (1994) discussion of thin-section petrography provide examples. Other contributions suggest the potential utility of new methods and techniques: Michele Derrick et al. (1994) discuss several possibilities, and Marion Mecklenburg et al. (1994) present the potential insights offered by computerized modeling of stress development. Still others seek to establish a foundation upon which solid advances may be made; Hansen's consideration of the effect of solvents on the physical properties of thermoplastic coatings (Hansen et al. 1991) and Michalski's (1990) proposed model of cleaning (varnish removal by solvent action) are of this type. Other contributions seek to establish general principles that can guide our thinking about a variety of materials and situations: the concept of solubility parameter (regarding solvent action) and Pourbaix diagrams (regarding the corrosion of metals) are prime examples. In any number of fields, a time-honored service has been to identify and begin to fill in significant gaps in current knowledge (Howie 1992; Williams 1993; Wilhelm 1993). A major area of activity aims principally to refine and enlarge upon presently available information; such would be the determination of both number average and weight average molecular weights of familiar thermoplastic resins, more precise data than had been available hitherto (de la Rie 1987). Table 1 summarizes just a few of the numerous objectives behind the research contributions that one will encounter.
TABLE 1 SOME RESEARCH OBJECTIVES IN CONSERVATION SCIENCE
The conservator probably does not see much in this list likely to be of immediate assistance in his or her work, partly because a significant investigative activity is missing: development. Calls for fulfillment of national needs in research and development (R and D) are familiar. Developmental research concerns the myriad problems associated with making untried ideas a practical success. Developmental research involves mission-oriented research, “the practical application of basic knowledge to attaining a specific goal” (NCAC 1979). The objectives cited in table 1 are not those immediately oriented toward the development of practical applications. They represent instead various aspects of the effort to build up the background of information needed to develop safe, sound, innovative, and practical methods of conservation.
A decade ago the effort devoted to developmental research in conservation was limited. Perhaps long-standing policies and practices of funding made it more difficult to obtain grants for development than for the acquisition of basic facts, information, and understanding. In addition, there were far fewer scientists in the conservation field than there are today.
Things have definitely changed. One finds increasing numbers of laboratories dedicated to support for developmental research in specific areas of conservation. Among others, there are now an Image Permanence Institute, a Leather Conservation Centre, a Laboratoire de Recherches des Monuments Historiques, Centro di Studio Cause di Deperimento e Metodi di Conservazione della Opere d'Arte, and a Centre for Archival Polymeric Materials. Most notable, of course, has been the major commitment of the Library of Congress and others toward developing a method of mass deacidification (Luner 1990). There is also considerable interest internationally regarding practical solutions to the consolidation of building stone (Baer et al. 1991; Rodrigues et al. 1992). The Getty Conservation Institute is currently interested in ways of preserving adobe.
Among these efforts are many basic studies undertaken to obtain supporting information. Does deacidification with calcium hydroxide protect paper against mold growth (Marconi 1989)? Does quartz or calcite interfere with the consolidation of stone by methyltrimethoxysilane (Denehey et al. 1992)? Such inquiries are rarely intended or ready for immediate application by the practicing conservator. Let us also admit that scientists often do not make their objectives clear. Nor is it always a simple matter to explain how a contribution is intended to fit into the larger picture. Perhaps it is assumed that these points usually should be rather obvious. It might be a useful exercise, nonetheless, upon being confronted with a rather involved report by a scientist, to speculate as to just what category of topic, such as those in table 1, it is intended to address. There is a further basic problem facing authors in this field: their presentation often must satisfy an extremely wide range of interested parties, extending from museum directors, curators, and practicing conservators to a peer group of conservation scientists as well as specialists in industry and academia. It is virtually impossible to accommodate all these interests in a single presentation.
There are not many occasions in which the research findings proceed directly to the practical end. Caution is certainly commendable if not mandatory. The case of soluble nylon provides a striking example in which a material was introduced directly into conservation practice. Sease (1981) and Hanna and Lee (1988) note that soluble nylon was first mentioned in 1958, recommended largely on the basis of some of its initial properties. Curiously, extensive aging tests were never carried out, nor was background information provided concerning whether this particular chemical substance was likely to be stable. It was more than a decade before a formal publication drew attention to potential problems (DeWitte 1975).