Rare Books and Old Materials Division,
Reference and Special Collections Department

This is based on an article of the same title
in NDL Monthly Bulletin No. 584 (November 2009).

Stack of the Rare Books and Old Materials Division, which mainly holds Japanese old materials of during/before the Edo era (1603-1867) and Chinese books of during/before the Qing Dynasty, is situated in the seventh basement of the Annex of the Tokyo Main Library. Among the old materials, 22,000 items designated as rare books or semi-rare books and equivalents are stored in the Rare Book Stack which is sealed off from the regular stacks by an airtight door. It is about 252 square meters. Being inside the stacks of the Annex, the Rare Book Stack is enveloped entirely by the stacks of the Annex which are, themselves, surrounded by the thick airspace of a light well (an atrium at the center), deep soil and a waterproof layer. This “stack in stacks” was completed in May 1992.

• Interior and shelves

Inside the stack, ceiling, wall and floor are finished with Hinoki (Japanese cypress) plywood. Shelves are made of Nara (kind of oak) with sliding doors (photo 1). It is intended to keep the materials from drastic changes in temperature and humidity. As cement and interior materials may become pollutants and damage the materials, we spent about nine months after the construction of the stack removing polluting factors. Materials were stored after a survey on the environment inside the stack had been conducted. However, as resin may be exuded from the timber used in the stack and the shelves, shelf boards are covered with thin acid-free paper to absorb resin. Acid-free paper is also used to cover the materials so that resin will not adhere to them (photo 2, 4).

Fluorescent light which cuts 99.7% of ultraviolet compared with the ordinary kind, is used. Staff are encouraged to turn off unnecessary lights.

• Temperature and humidity

The temperature in the stack is set at 22℃±2℃ and humidity at 55%±5%. Independent air conditioning is installed which is run only in the Rare Book Stack. Although an automatic monitoring system records the temperature and humidity every hour, the staff of the Rare Books and Old Materials Division also directly check the thermo-hygrometer twice a day to keep track of the condition of the stack (photo 3). As there is almost no change in temperature and humidity in the stack, it can be said that the storage environment is ideal. As movement in and out of the stack affects the temperature and humidity, only the staff members in charge are allowed to enter the Rare Book Stack.

• Dust and pests

Entering the stack is limited also to prevent dust and pests from coming in with a person. It is for this purpose that we wear slippers for internal use when entering the stack and use a special book-trolley when delivering materials (photo 5). We set up pest traps in various parts of the stack and insec repellent incense on each shelf to prevent pests which happen to enter despite above mentioned measures.

As countermeasures against dust, high air pressure is maintained in the stack to keep out dust, and cleaning is also conducted regularly.

Rare materials of the NDL are heavily guarded by carrying out these various countermeasures.

photo 5

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