Many books in libraries, museums, archives and private collections are deteriorating because of poor storage and handling practices, improper environmental conditions and neglect of preservation. Often these books are rare leather-bound editions or manuscripts. If not preserved, these collections will, in time, deteriorate beyond use. One of the important causes of deterioration of leather bindings is their absorption of atmospheric pollutants such as sulfur dioxide. Environmental conditions and other factors have a direct bearing on the condition of leather. Bindings, in time, lose some of their natural oils and fats, which serve as lubricants, preventing cracking during normal handling.