The Abbey Newsletter

Volume 19, Number 6-7
Dec 1995


Indoor Environment Standards:
A Report on the NYU Symposium

by Ellen McCrady

The press release issued by four scientists at the Smithsonian's Conservation Analytical Laboratory (CAL) last August generated controversy by stating that museum objects could tolerate wide swings in temperature and relative humidity (± 10°C and ±15% RH), and suggesting that museums could save millions of dollars in capital and operating expenses by adopting these new standards. (Abbey Newsletter, Aug.-Sept. 1994, p. 45)

The new standards were said by the CAL scientists to apply to all materials, including paper and photographs, and to cover chemical as well as physical changes. However, the published research they cited, most of which concerned physical reactions of materials like wood and acrylics, did not appear to support the new recommendations. (See sidebar.)

Norbert Baer and Paul Banks asked the four scientists to present their views June 23, in a one-day symposium immediately following a seminar they were giving on the indoor environment, at the Conservation Center at New York University's Institute of Fine Arts. (The preliminary program was published in the April issue of this newsletter.) In the end, there were ten invited speakers and close to 100 attendees, counting students and interested IFA staff. There are no plans to publish the proceedings, but most of the speakers have published previously on this subject. Representative publications are cited below in the list of references.

The first hour and a half was devoted to presentations by each of the four CAL scientists: Marion Mecklenburg, Charles Tumosa, David Erhardt and Mark McCormick-Goodhart.

Mecklenburg's talk was quite technical and had to do with expansion and contraction of test materials (wood, hide glue and acrylic paints) with fluctuations in RH and temperature. Internal stresses build up in these materials if they are restrained, and irreversible changes take place under extreme conditions when elastic limits are exceeded. There were a lot of equations and complex graphs, which it would be pointless to present here even if it had been possible to record them at the time. The idea was to base recommendations for storage conditions on knowledge of these physical properties and reactions in artifacts.

Tumosa gave facts and data supplementing those in Mecklenburg's talk: yield points in cottonwood and other wood samples, tests of white oak, moisture content, tangential and radial yield, and so on. He also discussed safe ranges for coatings, paints and wood (25%-70% for some, less for others), and distinguished between the yearly and daily variations within the "safe" range (35%-60%) at the National Air and Space Museum (NASM). The smallest allowable variations at the NASM are for materials on exhibit.

He showed a graph demonstrating a strong negative correlation between energy cost per square foot and RH fluctuations in each of the Smithsonian buildings. The smaller the RH fluctuations, the higher the energy cost per square foot. In one of the museums, which is held to 50% ± 2%, energy costs are $6 per square foot.

Erhardt said it was better to have controlled RH, but questioned whether it was worth the money. He said that there will always be objects that require special environments. Hydrates (a type of mineral) are not stable at any single RH; for weeping glass, 45% is the upper limit; and cellulose (his specialty) shows complex effects, with significant hydrolysis at high RH and crosslinking below 20% RH.

McCormick-Goodhart, a photographic scientist, spoke on specialized storage environments. Cold storage vaults are expensive to operate, but they do a great deal to extend the life of unstable photographic film. On removal from the vault, however, the unprotected film experiences a large change in RH. This effect can be prevented by storing the film in a five-part enclosure before putting it into the vault: a bag, a box, silica gel, and another bag with a cobalt chloride indicator. This would not control temperature, but it would at least keep the RH low. Taking the film out of the dry enclosure for use after it warms up would not shorten its life as much as taking the unprotected film out of cold storage would.

A session entitled "Environmental Management Tools" followed these four presentations. Speakers were Donald K. Sebera, James Reilly and William P. Lull.

Sebera described the isoperm, a graphic way of presenting simultaneously the probable effect of temperature and relative humidity on the life expectancy of library materials. With temperature along one dimension and RH along the other, a box can be drawn to show the range of target conditions, say 68-72°F and 35-45% RH; and a series of lines (isoperms) can be drawn to connect points that would result in the same life expectancy. The graph is good for communicating with engineers who are installing new HVAC systems or adjusting old ones, because it offers alternate ways of finding a satisfactory solution and gives the engineers some familiar concepts to work with.

Reilly described a shorthand way of assigning numbers to the life expectancy of an object or collection on the basis of the chemical reactions that result from temperature and relative humidity. It is called the Preservation Index or PI for short, and it is based on the isoperm. A table shows the life expectancy in years under different steady conditions. Another concept, the Time Weighted Preservation Index (TWPI), can be used to find life expectancy when changing conditions need to be taken into account over an extended period of time.

Lull has also put the isoperm to use in his work. Recently he used it to justify installation of a secondary chiller in the Catherwood Library, now under construction at Cornell University. He calculated that the storage conditions it would make possible could be expected to extend the life of materials from 50 to 100 years. Although the chiller cost a quarter million dollars, the argument was compelling, and the equipment was installed.

Dehumidification, he said, is more complex than humidification, but most systems can handle it for about $3 per square foot. If costs are higher than this at normal room temperature, something is wrong or wasteful. What usually goes wrong with humidity control is its location in the system. It does cost more, though, to remove water from cool air (40°-50°) than from warm air.

A session on case studies followed. Speakers were Stefan Michalski, a senior conservation scientist at the Canadian Conservation Institute (CCI); Adrienne Thomas, Assistant Archivist at the National Archives; and James R. Druzik, Conservation Scientist at the Getty Conservation Institute.

Michalski gave a talk that was humorous and indirect, saying he wanted his listeners to draw their own conclusions. For 16 years, he has been visiting and advising Canadian museums, libraries and archives about environmental conditions for storage and exhibition. In the field he observed many artifacts that did not suffer from uncontrolled environments (even when the RH varied over a 40% range), but he also saw some that did.

After a while, he saw that the picture was too complex to justify a "lowest common denominator type of advice," and accordingly began giving more careful and full advice, which only confused conservators. However, they did get used to the gradual liberalization of standards recommended by CCI, which now include seasonal variation of temperature and relative humidity, ±5% RH daily fluctuations, and even (for museums that close during the winter) control of RH rather than temperature. (To lower the RH, the temperature is raised, and to raise the RH, temperature is allowed to fall.)

This liberalization makes sense in a cold country like Canada, where an indoor RH of 50% in the winter would rapidly destroy many of the historic buildings that house museums, by causing condensation in the outer walls. In fact, many Canadian museums are small and old, and not able to push the RH that high in the first place.

Part of the complexity of the picture is that not all objects in a museum, or even all objects of the same sort (e.g., wooden artifacts) react to conditions the same way. In fact, he said, different parts of the same object react differently, depending on their past history, the materials of the different parts, and how they are assembled (e.g., cross grain vs. parallel grain, and amount of restraint). Generalizing from lab research on "little bits of new wood and new paint" to "artifacts" in the real world, he said, should make a person nervous.

He considers the whole debate about recommending ±15% RH to be entirely artificial. Instead, he made three points in his conclusion:

  1. It is important to avoid large deviations (±40%). Reliability of control is very important.
  2. Staying reliably within 20% of the local historic average is probably the most cost effective global advice.
  3. Diminishing steps of ±10% or 5% will bring real, but very much smaller, benefits. Each step is counterproductive if it comes with any increase in the failure rate. High-tech solutions that break down bring in a new risk.

Thomas described in general terms the planning that was done for environmental control in the new Archives building. There are two air circulation systems. The one for the stacks brings in less than 10% outside air. The standards for temperature and relative humidity were a mixture of the best information available (from inhouse staff and the National Academy of Sciences) and what was doable. The air is filtered and humidified or dehumidified as necessary, with six air changes per hour. Sensors are in the ducts. Operating costs are not known yet; they were still in the process of moving in at the time.

James Druzik reviewed more than ten years of environmental research at the Getty Conservation Institute, including a few comments on the planning for environmental control at the new Getty Center. Over half of the million square foot facility will have controlled relative humidity and temperature like that typically found in art museums. The other half, largely composed of offices, food services, and other support functions, will have the same tight temperature control, but relative humidity will be controlled only to keep it above 30%. The energy costs are predicted to be about $3.00 per square foot.

They recently did a study of the cost of environmental control for the Scott Gallery at the Huntington Library and Botanic Gardens in San Marino, and found by using computer simulations that the energy cost was not significantly higher for ±2% than it was for ±7% RH. They want to revisit this whole issue, to find out why their results do not agree more closely with the Smithsonian energy cost survey figures.

In the panel that followed the papers, each person was invited to comment. Only two people's comments are recorded here.

Steven Weintraub commented on costs and overdesign of museums. Engineers and architects, he said, are not good at communicating about costs or balancing them against preservation requirements. They want specifications, some numbers to work from, to protect them from lawsuits. If you give them a narrow range of variation like ±2%, this puts them into unfamiliar territory. Just to be safe, they install more equipment than they have to, and charge accordingly.

Paul Banks said he was very interested in David Erhardt's bar graph, which showed the widely differing safe ranges for various materials; it is not terribly different from conventional wisdom, he noted. He was also interested in Michalski's comments on overgeneralization, a common tendency. Conservators, administrators and scientists all sometimes want to extrapolate from a small piece of information.

Published Commentary

Several reviews of the symposium have been published since last June.

  1. Shin Maekawa, Head of Environmental Science, Getty Conservation Institute. Report and commentary in the column edited by Mary Piper Hough, "Conference Reviews," WAAC Newsletter, v. 17 #3, Sept. 1995, p. 20-21.
  2. Barbara Appelbaum, conservator in private practice. Commentary in the column edited by Mary Piper Hough, "Conference Reviews," WAAC Newsletter, v. 17 #3, Sept. 1995, p. 21.
  3. Carol Christensen, Painting Conservator. "Environmental Standards: Looking Beyond Flatlining?" AIC News, v. 20 #5, p. 1-2, 4-8.
  4. James Druzik and Paul Banks, "Appropriate Standards for the Indoor Environment," CAN 62/63, Summer/Fall 1995, p. 1, 3-8.

All of the reviewers summarized the presentations and commented on the CAL recommendations and/or the controversy in general.

Maekawa wrote, "The basis for CAL's environmental recommendations seems too narrow. It lacks consideration for objects with variations in construction materials, workmanship, material composition, and state of conservation.... The requirement should be set with these factors in mind, not from limited and simplified material test data."

Appelbaum said that many of the listeners who discussed the issues between sessions concluded "...that the press release was not very relevant to the actual research, and that the scientists involved had reached conclusions that are similar to observations made over long periods of time by conservators.... Major costs and limitations on humidity control are based on issues other than the degree of allowance specified... For those who deal directly with clients, introducing vapor barriers and reheat are major issues; the question of allowed fluctuations seems relatively unimportant."

Christensen felt that the CAL researchers were under attack, but could not understand why. The most eloquent speaker, in her opinion, was David Erhardt, "who at the end of the conference observed that anyone who challenges the status quo is subjected to minute and sometimes unpleasant scrutiny."

Druzik and Banks said that "most of the mechanics research carried out under the supervision of Marion Mecklenburg does not directly address the issues surrounding the chemical kinetics involved when materials age and degrade.... Libraries and to a slightly lesser extent archives, generally do not have the option of being able to provide microenvironments for the bulk of their collections, many of which consist of materials (especially paper and photograph materials) whose sensitivities to environmental deterioration are well established." At the same time, they agreed that it always takes energy to change the moisture content of the air, and that more tightly controlled fluctuations in relative humidity will consume more energy than more widely controlled fluctuations.

Editorial Commentary

This controversy came about, in my opinion, from not having in place the conditions that make good applied research possible. These conditions are particularly crucial when the work is being done for practitioners like conservators and administrators, who make serious decisions and carry out complex procedures, the consequences of which are often hard to evaluate. It is important to have their active participation. Otherwise no one can be sure that the problem is selected and defined properly, or that the proposed solution is workable. Similarly, the practitioners need the active participation of scientists when they are building their lists of needed research, so that they will identify only researchable, realistic topics, and ask questions for which answers have not yet been found.

In this case, it seems to me that good and productive communication between researchers and practitioners is sadly lacking. Channels of communication need to be opened up that will include scientists, conservators, and administrators. These parties need to meet from time to time, both on an institutional and a national basis, and talk seriously about what tends to go wrong. They need to do frank post-mortem analyses of individual cases of conflict, make specific recommendations, and evaluate the results of their efforts. It may be necessary to bring in a third part to facilitate communication, at least at first.

There is a wealth of research, mainly from the 1970s and early 1980s, on how to put the results of applied research into the hands (and minds) of the people for whom it was performed. The whole topic of applied research is reviewed in Putting Knowledge to Use: A Distillation of the Literature Regarding Knowledge Transfer and Change. (Human Interaction Research Institute, Los Angeles, in collaboration with the National Institute of Mental Health, 1976, 452 pp). It is possible to quote this book ad lib here because the work was done on a federal grant, and government-funded publications are not under copyright. In the quoted passages below, ellipses (...) often stand for long strings of citations.

Chapter 4 in Putting Knowledge to Use, "Research-Practice Linkage: Dissemination and the Change Agent," seems most relevant to the environmental control controversy. Under the first main heading, "Practitioner-Researcher Relationships," it summarizes research on differences and collaboration between researchers and practitioners.

The section on differences opens by saying, "Researchers and practitioners, especially in the social sciences, seem to inhabit two very different professional 'worlds.' An investigator seeking truth has a different set of values, problems, norms, and reference groups from those of a practitioner.... In discussing the relation of research to practice, Short (1973) describes the mismatch between the knowledge produced by researchers and that required by practitioners. He suggests that researchers should try to understand the complex ways in which knowledge is used in practice....

"Many researchers feel it necessary to communicate only with narrow publics of their intellectual discipline.... As a result, the written reports of in-progress or completed research appearing in journals make excessive use of academic jargon peculiar to a particular specialty.... The limited academic orientation of many researchers, according to Archibald (1968), signifies their evident belief that they have completed their commitment when they have reported to the funding agency or have published an article in an academic journal. Joly (1967) recognizes the gap between the researcher's language and that of the practitioner, and how it may result in mutual distrust and lack of communication."

The practitioner's ways of thinking are described next, and contrasted with those of researchers: "Rodman and Kolodny (1965) describe the research investigator as logical; the practitioner as intuitive.... Research attempts to discover common patterns in a population; the clinician views each case as unique. The scientist can live indefinitely with the tentative and hypothetical; the administrator wants to act with confidence. [Note: Most of the practitioners studied were taking care of people rather than artifacts, so the reader should make allowances where this seems called for.]

"...The manager or operator tends to seek a prescription--what to do (Glock, 1961). Careful tests of credibility are commonly used in research, less applied by practitioners (Flanagan, 1961). It seems that the practitioner, in order to improve his service, is likely to interpret and apply research findings beyond their limits of reliability and validity; then he may be disappointed and disillusioned."

So much for the description of only one of the obstacles (differences in thinking) to establishing good practitioner-researcher relationships, which in turn is only one aspect of success in doing applied research. Six factors associated with successful applied research are described under the next main heading, "Collaboration Between Researchers and Practitioners."

"[1] Of primary importance is the identification and development of a research problem that reflects the interests and concerns of those affected by the research project....

"[2] Another basic principle is that practitioners should be involved in all phases of the research. Once an area of research need is identified, the collaboration should continue through problem formulation, study design, data collection, interpretation of findings, and application of the results.... Not only can the practitioner make significant contributions to each of the research phases, but also effect participation of the eventual beneficiaries of research in its design, conduct, and evaluation. Those who have a significant part in planning and decision making are not only better informed but are more committed to making use of findings....

"[3] An important consideration is the need for the research team to contain a representative of the agency's top management. Fairweather (1967) and Glock (1961) emphasize that the person representing administration must have policymaking power....

"[4] Frequent honest and open communication between researchers and practitioners reduces the likelihood of the emergence of stumbling blocks in the study and enhances the chances that research findings will be put to use....

"[5] Another important step in preventing the development of later problems is early clarification of practitioner and administrator expectations of the research....

"[6] Research is also more likely to proceed smoothly when, before starting the project, there is a very explicit understanding between researchers and agency administrators regarding reciprocal responsibilities. [This may be less important in the field of conservation. -Ed.]"

These excerpts demonstrate, to some degree, that this research could be useful to the field of conservation research and practice. There are other books and journals, and one professional organization, in which the matter of applied research is occasionally discussed. The publications vary in quality. I am currently evaluating them.

Recent Publications by the Speakers

Druzik: "The Research Program of the Getty Conservation Institute." In Preservation Research and Development: Round Table Proceedings, Sept. 28-29, 1992. Edited by Carrie Beyer. Library of Congress Preservation Directorate, April 1993, p. 100-102. This describes the GCI's research program and how it has been reorganized to facilitate diffusion and utilization of research results.

Erhardt: See sidebar; also "Accelerated vs. Natural Aging: Effect of Aging Conditions on the Aging Process of Cellulose," by David Erhardt and Marion Mecklenburg. Pages 247-270 in Materials Issues in Art & Archaeology IV (Vol. 352--Proceedings from the 4th Symposium on Materials Issues in Art and Archaeology, May 16-21, 1994, Cancún, Mexico). Announced on p. 60 of this newsletter, Aug. 1995.

Lull: (With the assistance of Paul N. Banks), Conservation Environment Guidelines for Libraries and Archives. Canadian Council of Archives, 344 Wellington St., Rm. 1009, Ottawa, ON K1A 0N3, Canada, 1995. 192 pp. $17.50.

McCormick-Goodhart: See sidebar.

Mecklenburg: See sidebar.

Michalski: a) "Museum Environment Specs Revisited. Again. Oh God, Not Again." IIC-CG Abstracts, Calgary, May 26-28, 1995. (Reviewed on p. 117-119 of the Dec. 1994 Abbey Newsletter) b) "Relative Humidity and Temperature Guidelines: What's Happening?" CCI Newsletter No. 14, Sept. 1994, p. 6-10. c) "Relative Humidity in Museums, Galleries, and Archives: Specification and Control." In Bugs, Mold and Rot II, Proceedings of the Workshop, Nov. 16-17, 1993, p. 51-62. Edited by William B. Rose and Anton Ten-Wolde. National Institute of Building Sciences, Washington, DC, 1993.

Reilly: James M. Reilly, Douglas W. Nishimura, and Edward Zinn. New Tools for Preservation: Assessing Long-Term Environmental Effects on Library and Archives Collections. Commission on Preservation and Access, Nov. 1995. 35 pp. $10.00

Sebera: Isoperms: An Environmental Management Tool. Commission on Preservation and Access, June 1994. $10.00.

Thomas: No publications found.

Tumosa: See sidebar.

Some of the papers that report the results of CAL's five years of environmental research are:

1. Mecklenburg & Tumosa, "Mechanical Behavior of Paintings Subjected to Changes in Temperature and Relative Humidity," in Art in Transit, ed. M.F. Mecklenburg (Washington: National Gallery of Art, 1991), 173-216.

2. McCormick-Goodhart and Mecklenburg, "Cold Storage Environments for Photographic Materials," IS&T 46th Annual Conference, 1993, p. 277-280. (IS&t=Society for Imaging Science and Technology, formerly the Society of Photographic Scientists and Engineers or SPSE.)

3. Mecklenburg, Tumosa & Erlebacher, "Mechanical Behavior of Artist's Acrylic Emulsion Paints under Equilibrium Conditions, Polymer Preprints (American Chemical Society), v. 35 no. 2, 1994, p. 97-98.

4. Mecklenburg, Tumosa & McCormick-Goodhart, "A General Model Relating Externally Applied Forces to Environmentally Induced Stresses in Materials," a paper given at the Materials Research Society (MRS) in Cancún, Mexico. 8 pp.

5. Mecklenburg, Tumosa and Wyplosz, "The Effects of Relative Humidity on the Structural Response of Selected Wood Samples in the Cross-Grained Direction," a paper given at MRS in Cancún. 20 pp.

6. Erhardt & Mecklenburg, "Relative Humidity Re-examined," in Preventive Conservation: Practice, Theory and Research, Preprints of the Contributions to the [IIC] Ottawa Congress, 12-16 Sept. 1994, p. 32-38.


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