November 25, 2013
Monitoring the Environment
If asked, many people would define a library as a building that houses books. While this is an adequate description, many people don’t realize the sheer amount of personnel, knowledge and work needed in order to keep a library running smoothly, efficiently, and into the future. Books don’t magically appear on the shelves, nor do they stay pristine since their acquisition. Like objects and paintings in a museum, books prefer certain environmental conditions.
Two of some of the most important controllable conditions (non-controllable would be: theft, fire, dog-chewing, etc.) are temperature and humidity. Since books are made of different materials such as paper, cloth, leather, glue, etc., determining an ideal environment is tricky. Each material has its own perfect temperature and humidity level that would ensure longevity, yet not inflict damage.
Extremes should be avoided, as these are the most likely to cause damage to library collections. The fluctuation from one extreme to another forces the materials of the book to expand and contract. Even though the materials used to make a book are different, many are hygroscopic, as they readily absorb and release moisture. And since there are different materials, they do this at different rates. These changes affect the very structure of the book, but extreme changes in temperature and humidity also encourage chemical and biological changes to occur. For example, if the area is hot and dry, the acids within the paper of the books accelerate to make the pages brittle. A brittle page is more likely to break rather than be turned or folded. However, if the area is humid, then mold is likely to form, which can stain pages, spread to the rest of the library, and pose a health concern.
Where a book is placed is of great concern if the book’s future is valued. Keeping in mind the guidelines for temperature and humidity, book shelving should not be placed on outside walls. For those who have spent any time here in Ohio, it’s a well known fact the temperature gets very cold for a good deal of the year! Walls, and the shelving on them, that have a face to the outside are more susceptible to wild temperature fluctuations than those within the building. While the chilliness of the air may be beneficial to the books, the dampness contained within that air could be detrimental. Inside factors must be taken into account as well, as books placed near radiators or air conditioners also face those great fluctuations.
Ideally, books should be kept in a cool, dry, and dark place. However, this is far from ideal if the book is to actually be used.
Many conservators recommend that an acceptable environment for books that are in circulation would be a temperature of about 70°F, with a relative humidity roughly 50%. However, these numbers are guidelines, and while they are important, it is better that the items have a stable environment, rather than one with a perfect temperature or humidity. In order to monitor these conditions, Kelvin Smith employs the use of HOBOs.
HOBOs are a type of data logger produced by the company Onset, and shown here roughly actual size. While there are many types of data loggers to choose from, which can log information on anything from temperature to voltage to light intensity, the HOBOs Kelvin Smith uses record those two conditions that are very important to the longevity of books: temperature and humidity. The data loggers are strategically placed in collections at high risk of damage and are checked routinely. The HOBOs collect the temperature and humidity levels once every hour, and every month this information is downloaded. Through the software that came with Onset’s HOBO data logger, the information can then be graphed, saved and analyzed.
Throughout other parts of the library, thermo-hygrographs keep a vigil on the environment as well. This information provides personnel a picture of what is going on temperature and humidity-wise within the library, and allows them to take action if necessary.
For more on caring for books, and other objects, the American Institute for Conservation of Historic and Artistic Works has a lot of great information, as well as the
Northeast Document Conservation Center.