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The MOAH Move and the Importance of Proper Temperature Controls in a Museum

The Lancaster Museum of Art and History (MOAH) will be closed from August 22, 2022 to May 12, 2023 for HVAC improvements. During this closure, the public is encouraged to visit the museum’s other locations: MOAH:CEDAR, the Elyze Clifford Interpretive Center, and the Western Hotel Museum. These locations will remain open with new, extended hours to accommodate the main facility’s closure. The museum will reopen on May 13, 2023 with a brand-new exhibition co-curated by Dr. Betty Ann Brown.


The History of MOAH’s building

A proper HVAC system is necessary for the care and maintenance of a museum. What is now the MOAH office building was once a bank teller’s office (See Figures 1-3). In the building’s construction photos from 2011, you can see the original brick wall that was in place before MOAH was constructed. The original bank vaults and walls are still in use today within MOAH’s collections department offices in the basement. The gallery spaces were then added onto this existing structure (See Figures 4-6). This building was never properly equipped to function as a museum and was thus lacking the proper air conditioning and humidity controls.


Standardizing Temperature and Humidity

Within museums, we house many different types of items in our collections. Each type is made from unique materials that can each be best preserved in certain climatic conditions. For many years, museums adhered to certain ideal conditions of relative humidity and temperature to protect their objects from mold, cracking, warping, shrinking, and other forms of decay. Recent movements to standardize museum care have resulted in the creation of the American Institute for Conservation of Historic and Artistic Works (AIC) group which works to provide recommendations and guidelines for conservation work within museums. With the improvements of air conditioning technology overtime, standards for temperature and relative humidity have been created to ensure a suitable environment for many types of artifacts. Conditions of 50% ±5° relative humidity (RH) and 70°F ±2° (called “50/70”) have become a general guideline for most museums (Hatchfield).


How Temperature Changes Affect Collections

Temperature changes affect objects in a variety of ways. As outlined by the National Parks Handbook for museums, as the temperatures of objects change, objects will reach thermal equilibrium and adjust to the temperature of their surroundings. Increased temperatures typically cause the expansion of an object and decreased temperatures cause contraction. These fluctuations in temperature can cause accelerations in the chemical, physical, and biological processes that cause deterioration (National Parks Museum Handbook).

For higher temperatures, chemical reactions can increase- which is especially an issue for acidic paper, plastic, and photographic materials. Certain types of film can even catch on fire if exposed to high temperatures for prolonged periods of time. Higher temperatures can also cause objects to lose moisture from evaporation which can lead to cracking and deformations. In addition, higher temperatures cause increased biological activities, such as the spreading of molds and breeding of insects. Materials can also soften, including waxes which can collect dust more easily and become sticky (National Parks Musuem Handbook).

At lower temperatures, objects can become more brittle and can crack, flake, and have other damages. Materials such as varnishes, lacquers, wood, oil, alkyd, and acrylic paints are especially at risk and need to be handled with extreme care (National Parks Museum Handbook).

Fluctuations between hot and cold temperatures can cause materials to expand and contract quickly, which places destructive stresses on the object. Fluctuations that occur faster than the object can adjust to the changes can cause cracking or exfoliating (National Parks Museum Handbook).


How Humidity Changes Affect Collections

Humidity is generally measured as a ratio known as relative humidity (RH). RH is the mass of water vapor in a fixed volume of air and the maximum mass of water vapor that a fixed volume of air can hold at the same temperature. The relationship between temperature and humidity is that for a given volume of air, as the temperature rises, the humidity decreases and vice versa (National Parks Service). Understanding and monitoring relative humidity within a museum is important because water has a large role in various chemical and physical deteriorations. Deterioration can occur when RH is too high or too low or fluctuating. Moisture can come from various places, including exterior humidity from rain, pools of water, wet ground, broken pipes, moisture in the walls, from respiration as well as perspiration, and general cycles of condensation and evaporation (National Parks Museum Handbook).

In addition, all organic materials and some inorganic materials absorb and give off water depending on the relative humidity of the surrounding air. This can cause damage to certain items such as faster corrosion with metal objects at higher RH levels. Pests and mold grow with higher RH and shrinking, and cracking can occur at low RH levels in organic materials (National Parks Museum Handbook).


Improving and Maintaining Our Collections

It is because of these risks to our collections that MOAH has advocated for our HVAC system to be improved. The improvements to our HVAC system will allow us to have a reliable, steady temperature and humidity control. We will continue to have climate control readers in place within our different galleries to monitor changes in humidity and temperature to ensure that our items are preserved.


Figure 1: MOAH during construction in August 2011


Figure 2: MOAH Library 2/14/2012 with original brick walls from bank office


Figure 3: MOAH Library board room 2/24/2012 with original brick walls from bank office


Figure 4: MOAH Classroom under construction in 2011


Figure 5: MOAH entrance lobby under construction in 2011


Figure 6: MOAH entry lobby under construction in 2011


Works Cited


Hatchfield, Pamela “Crack Warp Shrink Flake: A New Look At

Conservation Standards”, January/February 2011 edition of Museum magazine.

National Parks Service

The Museum Handbook Part I: Museum Collections


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