April • 2015
Managing Archive Preservation
It is critical to the conservation of historic and artistic works to understand how environmental conditions can effect the speed at which deterioration can occur.
Natural aging, mechanical decay, mold, and metal corrosion can be controlled within the proper environment, significantly reducing the likelihood of deterioration and damage.
Relative Humidity determines how much moisture collection objects will contain. High Relative Humidity will leave objects too damp, while low Relative Humidity will leave objects too dry.
The amount of moisture in organic collections such as wood, paper, paint, magnetic tapes, etc., and on the surface of inorganic materials such as stone and metals, can be predicted best by Relative Humidity. High relative humidity increases the chemical reaction rate resulting in product decay.
Temperature is the most significant determinant of the rate at which items will naturally age.
At higher temperatures, atoms and molecules move faster. Because they are moving faster, chemical reactions occur more quickly. Thus, higher temperature increases the rate of decay, a chemical reaction. For most materials, the rate of decay is unacceptably fast at temperatures humans find comfortable.
Dew point measures the absolute moisture content of the air. It determines how much moisture is needed in the space to achieve the appropriate Relative Humidity in your storage environment.
Climate control systems use humidity parameters established from the dew point temperature to slow the deterioration process.
Even in warm climates, low indoor relative humidity can be problematic during winter months. As moisture is reduced in the outside air, the dew point drops in the outside and the inside air.
•At constant temperature: Relative Humidity and Dew Point will increase/ decrease together
•At constant Relative Humidity: Temperature and Dew Point will increase/decrease together
•At constant Dew Point: As Temperature increases, Relative Humidity will decrease, As Temperature decreases, Relative Humidity will increase
Humidifiers and dehumidifiers can artificially maintain dew point levels to ideal levels. System monitoring of temperature, relative humidity and dew point promote longevity of archived materials.
Sustainable Preservation evaluations include review of HVAC mechanical systems, design plans, optimal performance reviews and energy savings opportunities
Image Permanence Institute Director, James Reilly, explains how IPI's tools and analysis methods have lead to a management approach that balances the long-term preservation of collections with the sustainable operation of mechanical systems. By considering the general equilibration rates of collection materials and using the Preservation Metrics to interpret environmental data, IPI believes it is possible to implement energy-saving HVAC operations that could benefit long-term preservation of collections.