Art Museums Battle Deadly Contaminants
By Susan English
Museums wage a never-ending war against pollution and decay. Like national parks, fine arts and other museums suffer if the delicate balance between enjoyment and consumption is violated. Not surprisingly, most of the pollutants that make people sick make objects sick, too.
Wooden exhibition cases and storage cabinets emit acids and formaldehyde which corrode the very objects they are designed to display or store, while pollen and insect eggs, transmitted by outside air, can decimate botanical, as well as “dry” collections. Even rugs, varnishes, and the paint on walls put out corrosive chemical emissions. If that weren`t enough, consider that an expensively filtered, carefully controlled mini-climate in a storage area can be sabotaged by the opening of a door; sulfur dioxide can find its way into the museum`s rooms from passing traffic; and last but not least, the aficionados passing through the turnstiles bring in a whole other world of pollutants.
To deal with these challenges integrated systems of test management, constant air sampling and monitoring for impurities are common to most institutions. For example, at the Smithsonian Institution`s Center for Museum Support (Suitland, Maryland), Director Vincent Wilcox defines the goal: “to provide the optimum environment for the long-term preservation of our collections, as well as to provide the best environment for their research and study.” The problem, he says, is that the “best environment for preservation” is not the best environment for research and study. “We`re here to preserve as well as to use. The question is, how do we walk the line between making it available for the current generation and saving it for future generations?”
Pollution control begins with the proper regulation of air temperature and humidity in the building itself, storage areas, work spaces, exhibit rooms and display cases. Air filtration systems winnow out impurities in the air coming into the museum from the outside. Climate control systems regulate the air inside the museum, keeping it flowing constantly at the right temperature and degree of humidity (usually “ramped” at 50 percent +/-5 percent).
At the Smithsonian Institute, HEPA filters, designed to filter out 99.9 percent of all particulate matter, are used throughout the entire air system. The Institute encases them in pre-filters which first trap the larger particles. HEPA filters are also effective in trapping pollen and insect eggs.
But, HEPA filters or hospital standard filtration systems are not always affordable or even practical in older museum buildings. Arthur Beale, head of Harvard University`s conservation facility for over 20 years and presently serving as Director of Objects Conservation and Scientific Research at Boston`s Museum of Fine Arts, talks about filtration systems at the Museum: “Hospitals and museums have one thing in common: they`re all poor! So, in some instances the kind of filtration we would like to install–and we only have it in limited areas–is charcoal filtration and/or permanganate or formaldehyde.”
Beale describes some of the more exotic systems that the museum has tried. Purification systems based on experiments in the medical field with blood purification are sometimes used to remove the mineral content of water used in humidification systems. Some of the biocides used in steam-treatment and humidification systems actually cause metals to corrode, so some systems work osmotically to take out mineral material.
The varied nature of museum functions and spaces, artifacts and exhibits more often than not demand a “micro-climate” or “clean-case” approach versus that of a “cleanroom” and is easier to adapt to serve the needs of both museum staff and the public.
Museum storage areas, although requiring more limited access, take such precautions as air-sampling devices and self-ventilated storage cabinets to prevent buildup of gases or fumes. This includes the testing of floor tiles, adhesives, paints, and rugs.
In the museum exhibit rooms themselves, the area is usually divided into the “inside case” or micro-environment, and the area outside the exhibit case, the macro-environment. The most recently discovered danger to museum collections in exhibit cases is that of formaldehyde outgassing.
This phenomenon is caused by the use of formaldehyde-based resins in construction materials such as plywood and particleboard, as well as foam insulation and gasketry. The damage is easily identifiable as a white crystalline growth on materials such as metals, stone, and ceramics. Even very small amounts of formaldehyde, well below the national threshold for health and safety, can cause damage.
In their publication “Formaldehyde: How great is the danger to museum collections?” Pamela Hatchfield, Assistant Conservator at Boston`s Museum of Fine Arts` Research Laboratory, and Jane Carpenter, Assistant Objects Conservator at The Brooklyn Museum (Brooklyn, NY), provide state-of-the-art research findings on the effects of formaldehyde on museum collections and ways to either mitigate or solve the problems produced by aldehydes as well as organic acids. The use of ventilation, vapor barriers, paintings, coatings, sealants, formaldehyde “scavengers,” fumigation, sorbents, and radiation are some of the means discussed.
Natural history museums have their own particular set of contamination problems. When combined with oxygen and moisture, formaldehyde produces formic acid, which is very corrosive to shell and mineralogical collections. Other acids are also common problems, such as acetic acid, which is emitted by fruitwoods, and tannic acid from white oak. To combat these acids, passive filtration systems, including such scavengers as Purifil, Permanganate, and charcoal are used inside cases to absorb the destructive emissions.
Lead is highly susceptible to acid, so small chunks of lead called “coupons,” 1/2 in.2 by 1/8 in. thick, are placed in cases to detect the presence of corrosives. The negative consequences of natural compounds on so-called “dry” collections such as natural fibers, baskets, and tapestries also must be closely monitored. Volatile corrosion inhibitors are sometimes used to protect highly polished metals.
The Smithsonian Institute goes to great lengths to protect its Antarctic Meteorite collection. In fact, the facility housing it was constructed with the same installation specifications as those used at the Johnson Space Center to protect its Moon rocks. Because the meteorites had originally fallen into the “deep freeze” of the Antarctic Ocean, they were brought to the institution relatively free of contaminants. They were then stored in large cylinders filled with dry nitrogen gas, where they can be seen from a special viewing chamber. Every effort is made to ensure that the original mineral content is not altered, and that the surrounding environment is kept free of dust.
The Smithsonian`s Museum Support Center, is an 11-year-old, state-of-the-art collections storage and research facility consisting of 600,000 ft.2 of storage space and a number of very sophisticated research laboratories.
Very tight environmental controls are maintained in specialized storage and laboratory areas such as the Laboratory for Molecular Systematics, the Conservation Analytical Laboratory and others. To ensure optimal levels of dust-free air, Support Center Director Vince Wilcox devised a special cleaning system by installing HEPA filters throughout the facility`s vacuum cleaning systems. He feels they significantly reduce cleaning time and effort.
Also at the Support Center are several cleanrooms of varying grades in which are housed the Smithsonian`s research laboratories. At the Conservation Analytical Lab (CAL), research on the preservation of macromolecules in fossil samples is carried on in a positive pressure room. In this 6 ¥ 12 ft. HEPA-filtered cleanroom, all incoming air is pulled through seven filters, then cycled out through louvers located at the bottom of the room.
Museum directors agree: while they are entrusted with the care and preservation of valuable historic collections for the use and enjoyment of posterity, they cannot lose touch with the outside world they market to. They are constantly walking the line between preservation and use–preserving the building and its collections and providing services to museum employees and the general public. It`s a delicate contamination-control balance. n