Arid

This climate is generally very dry, however, in arid areas, it is often very hot during the day and very cold at night. This wide fluctuation in temperature is matched by wide fluctuations in relative humidity, for example from 75%–20%RH in a day.

When caring for books in arid areas it is important to note that:

• insects can still survive and can still damage your books;

• adhesives tend to dry out and lose flexibility, so care should be taken to open books gently;

• leather can also become very dry and lose flexibility; and

• in many arid areas there is a lot of dust and grit. For this reason book collections should be cleaned regularly. Remember grit can scratch some binding materials, so clean with care.

Remember that even arid areas can experience large fluctuations in relative humidity and temperature. You may wish to store your books in boxes or wrappers to provide them with a layer of protection from grit and fluctuations in relative humidity and temperature.

Note: If your books have been stored in an arid environment for a considerable period and they are stable—do not try to alter the environment to meet the recommended ideal conditions. This could do more harm than good. The emphasis should be on long term stability.

Temperate

A temperate climate is considered a moderate climate, however, temperate climates tend to have a greater range of temperatures than tropical climates and may include extreme climatic variations.

• It is probably easier to come close to the recommended ideal conditions for the storage of books in a temperate climate, however, it is unlikely that you will be able to maintain an even environment without the help of sophisticated air conditioning equipment.

• The system of layers of storage—wrappers, boxes, boxes within cupboards—will be very useful in helping to buffer against the extreme conditions that can occur in a temperate environment.

• As for all climatic zones, regular inspection of storage and display areas is important so that developing problems do not go unnoticed.

Note: If your books have been stored in a temperate environment for a considerable period and they are stable—do not try to alter the environment to meet the recommended ideal conditions. This could do more harm than good. The emphasis should be on long term stability.

Tropical

These climates are characterised by heavy rainfall, high humidity and high temperatures.

When caring for collections in high humidity conditions it is important to note that:

• closed books take up moisture, but are not well ventilated, thus creating an ideal environment for mould growth and for some insects;

• the rate of fading of book spines exposed to light is likely to be higher than in lower humidity conditions;

• adhesives used in the book's construction could take up moisture and become tacky and increasingly attractive to insects and mould;

• leather can become mouldy quite easily;

• some bookcloths will stick to each other if they become moist. Damage can be caused when separating them; and

• the different components of the books will take up moisture at different rates and this could lead to warping of the binding.

Regular inspections and maintenance of your book collection is important. You may be able to stop an insect or mould infestation before a great deal of damage is done. Open the books and allow air to get to the pages.

Note: If your books have been stored in a tropical environment for a considerable period and they are stable.—do not try to alter the environment to meet the recommended ideal conditions. This could do more harm than good. The emphasis should be on long term stability.