Timber
Timber contains a great deal of moisture when felled, which makes it almost impossible to work. It also shrinks as it dries out and often cracks. So, the wood gets seasoned. Seasoning involves stacking the wood for long periods in dry air to allow the moisture to evaporate.
Even after seasoning however, wood can still warp and twist when in use. This happens because wood is hygroscopic - it absorbs water from a moist atmosphere (causing it to expand) and loses water in a dry atmosphere (causing it to contract). A timber, which is prone to this problem, is said to be unstable. …
