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InfoGuides | Pepperdine Libraries

Preservation of Cultural Heritage: Temperature and Humidity

Learn about preservation of cultural heritage at Pepperdine, and what you can do at home.

The Problem With Temperature and Humidity

While the components in cultural heritage materials deteriorate on their own, adding heat and moisture accelerates the harmful chemical reactions of deterioration considerably.

When higher temperatures are present, molecules move faster and collide more frequently, making chemical reactions - including those that cause deterioration - more likely. In fact, an increase of 18 degrees Fahrenheit (or ten degrees Celsius) can double the rate of many chemical reactions.

High levels of relative humidity, or the amount of water vapor in the air relative to the amount the air can hold at its current temperature, can also speed up chemical reactions as moisture is a key component needed for the chemical and biological processes important in cultural heritage objects. In addition, many objects absorb and release moisture in order to come to equilibrium with the environment around them. Humidity fluctuations can therefore strain the objects and lead to breakage.

Finally, when relative humidity increases, especially alongside an increase in temperature, mold spores can activate and grow on objects. Fungi digests organic materials, which weakens the materials, and causes staining on items such as paper and book bindings.

Examples

Evidence of mold damage due to high levels of humidity.

Prior to their arrival at Pepperdine, these photographs were stored in a garage in a desert area, where extended exposure to low humidity caused the photograph supports to curl. Through hydration, we were able to flatten these photos so they can be viewed, and through storage in improved conditions, we can prevent this kind of damage from happening again.

Preservation Strategy

With the support of the National Endowment for the Humanities (NEH), Pepperdine commissioned a custom-built heating, ventilation, and air conditioning (HVAC) unit capable of maintaining consistently low temperature (60°F) and relative humidity (40% ) within collection storage areas. In addition to high-tech monitoring within the equipment itself, the Libraries also deployed temperature and humidity monitors throughout the space to gather temperature and humidity readings every five minutes. Data from these units are used to analyze and adjust HVAC settings as needed. Based on preliminary data, we have more than doubled the usable life of our collections since building the climate-controlled preservation environment.  

LET'S BE GREEN

Replacing an out-of-date, manually-controlled HVAC system with a new, automated, highly controlled system significantly reduces energy consumption. In addition, our sustainably-designed ceilings, walls, and insulation provide for vapor control, and a low number of air exchanges with the outside environment mean that the climate remains very stable within the room. This limits the time that the HVAC system needs to be active, and results in significant energy savings.