In the process of preservation and maintenance of paper works, attention should be paid to the location or storage environment that most directly affects the safety of the works. Controls are mainly aimed at the following directions:
(1) Light
Ultraviolet (UV) light in the light can cause photochemical reactions in the paper, which can reduce or embrittle the paper, and can also discolor the paper or media. If there are windows in the warehouse, paste UV-filtering heat insulation paper and install curtains or seal them directly. All indoor lighting must use non-ultraviolet lamps, and there must be no light sources except for safety lighting and escape exits. In addition, managers must regularly monitor the illuminance and UV intensity.
(2) Temperature and relative humidity
The paper will gradually accelerate the deterioration reaction in the environment of unstable temperature or violent change, resulting in the decrease of paper strength and discoloration. The humidity will directly affect the strength of the paper. When the relative humidity is 40~50%, the paper strength is the strongest. If the humidity is too high, the humidity will soften and tear easily. If the humidity is too low, it will be brittle. In order to avoid paper deterioration and inhibit the growth of insects, it is recommended to use temperature and humidity sensors to strictly control temperature and humidity changes, which must be strictly implemented.
According to the collection standards, the temperature standard for paper national files is currently set at 21±1°C, and the relative humidity is set at 45±5%; for institutional files, it is set at 27°C and below 60%. The warehouse of the National Palace Museum is set at 20~22°C, 50~60%, and the exhibition hall or showcase is set at 19~23°C, 50~60%, based on the principle of stable temperature and humidity. The warehouse of the Taipei Fine Arts Museum is set at a temperature of 20°C±2°C and a relative humidity of 50%±3%. The temperature and humidity settings of the above units are for reference only, and are still mainly based on the collections and considerations of each museum.
(3) Air pollutants
Outdoor air pollutants include oxides (NO, O3), acidifying substances (nitric acid), sulfides (acid rain, SO2), which accelerate paper embrittlement. Indoor air pollutants include building materials, shelves, adhesives in compartments, paints, cleaning agents, and also release organic gases such as formaldehyde, toluene, and chlorine. These pollution sources will release substances that are not only harmful to the human body, but also cause the deterioration and decay of paper works in the long run. Gas monitoring is also required.
(4) Insect and fungus problem
Insects are pests to managers as long as they cause harm, and both pests and molds grow when the temperature is warm and the humidity is too high. When pests nibble on paper substrates or media, the acidic excrement directly degrades the paper and leaves stains. Mold will decompose cellulose, destroy paper strength, and pigments in the body will leave mildew spots. This biological secretion and spots are extremely stubborn, and it takes a very high time and cost to deal with. In order to reduce the problem of insects and bacteria, it is necessary to control the temperature and humidity of the environment and carry out personnel entry and exit. It can be seen that real-time monitoring of temperature and humidity is one of the important measures to protect collections.