People always ask me about environmental requirements for art; it is based on the needs of the materials from which art and fine antiques are created: paintings, works of art on paper, and sculpture and objects, including outdoor sculpture. The most devastating of environmental conditions for interior collections are light and humidity. This paper is the most advanced information now available.
Generally, in homes and small offices, temperature and humidity are easily controllable with today’s air conditioning and dehumidification systems. Ideally, humidity would be kept constant between 50% relative humidity (RH) and 60% RH, with as little deviation from this range as possible. Mould forms above 70% RH, and once it germinates, it can maintain itself and grow in as little as 50% RH; wood, paper, and canvas desiccate below 35% RH, becoming dry and brittle. Temperature is not as important, except as it affects the ability of air to hold moisture. Cool is better; elevated temperatures (above 85° F) are not desirable. Controlling conditions in offices in large buildings is more difficult – actually, nearly impossible because owners rather than tenants don’t want the added expense of electric over night and on weekends. In structures where it is difficult, or impossible to maintain balanced temperature and humidity, select sculpture and objects unaffected by fluctuating conditions and sealed framing systems (described later) are often an ideal solution.
In residences, most of the humidity related problems we see arise from those balmy days when windows and doors are thrown open. During those times, the operation of ceiling or floor fans is desirable, since moving air reduces humidity and inhibits the formation of mold.
Light is the single most destructive environmental hazard. A new generation of ultraviolet (UV) filtering glass is available. Also, highly effective UV filtering films delete up to 99% plus of UV; the film is invisible when applied to existing glass. Most frequently we install clear, colorless UV film. Some films also are reflective or darkening films to control both heat and UV. However, there are some caveats:
- Diminishing the transmission rarely means eliminating UV. It only lowers the amount of UV transmission causing deterioration, and extends the life of UV sensitive materials like paper, wood, leather, canvas, and other textiles.
- Light deterioration from UV and the near blue range of the light spectrum is both cumulative and irreversible. Faded colors or brittle materials can not be restored.
- The near blue range of the natural light spectrum is nearly as destructive as UV and cannot be successfully filtered.
In short, it is still wise to keep UV sensitive materials away from direct natural light, and unfiltered florescent light. Only unpainted stone, metal, and unglazed/unpainted ceramics are completely suitable for display in direct light or sunlight.
Frequently cycling air conditioning and other fluctuations in humidity create dimensional stress in hygroscopic materials. Essentially, they are those which absorb and dissipate moisture in relation to their surrounding environment: paper, canvas, wood, ivory, leather, and textiles are the most common. In high humidity, they physically expand, but contract and shrink in low humidity. All of us have seen examples of dimensional change like sticking drawers and doors in rainy weather. Over time, multiple dimensional changes create “dimensional stress.” Some of these are permanent and irreversible; cockling and buckling works on paper, flaking paint on paintings and other painted surfaces, sagging or loosening veneers in furniture, and sagging textiles are among them.
Obviously, many fine pieces have come down to us through the centuries relatively unaffected by dimensional stress. In fact, most pieces can cope with dimensional change if the change is gradual, as it is in changing seasons; which was prevalent before modern temperature/humidity control. But with modern hearing and air conditioning, we expect a sweltering room to cool in twenty minutes. This constant stress places an accelerated strain upon fine pieces, and can result in dimensional failure with damaging consequences. Many conservators believe these accelerated stresses exceeds the sum of stress previously experienced during the entire life of the piece. In hot, humid areas the judicious use of air conditioning and dehumidifiers will help to slow the rate of dimensional change, easing the collection through RH changes.
There are essentially two ways to approach collections care: micro or macro.
The “micro” approach to collection care relies upon the individual needs of different materials. Some works, such as valuable furniture, rely heavily upon macro environmental management; that is controlling the entire house or office. Others, such as works on paper (depending on their size) can rely almost totally on micro management In following blogs a listing of the most common art objects and works, by category (paintings, outdoor sculpture, et al) with recommended management followed by danger signs.
Future blogs will address paintings, art on paper, furniture and wood, textiles, stone and outdoor sculpture, metals, glass and ceramics.