To preserve the objects collected and thereby prevent them from deteriorating, they must be placed in the appropriate conditions. Several factors can accelerate the deterioration of the items: humidity, pests, dust, light and temperature are all among the enemies of preservation.
The collector must not eliminate humidity, but rather control it; each object has its own ideal humidity level. Many objects react strongly to variations in humidity in the air. When the level is too low, organic materials such as skin or leather may crack. When the humidity is too high, mould may be seen to appear on organic materials, and oxidation (rust) can be seen on metals. Also, in an environment where there is considerable variation in the rate of humidity, some objects may be subject to repeated swelling and shrinking, which can lead to their breaking.
To measure the relative rate of humidity a hygrometer is used. As a general rule, the relative humidity should be kept between 40 and 60 % to avoid damaging objects and prevent the appearance of mildew. At home, we suggest that collections not be stored in an unheated space because there are often great variations in humidity and temperature.