Paper produced prior to the mid-nineteenth century was made from cotton and linen rag. Rag paper is usually alkaline or pH neutral. This older paper can last for centuries without becoming brittle. Paper produced starting in the mid-nineteenth century was made from materials that had an inherently high level of acid, such as wood pulp. When this acid paper is subjected to extremes in temperature or humidity, or is exposed to UV light, the acid in the paper will cause the paper to become brittle. Brittle paper turns yellow or brown and will crumble easily.
As library collections age, many books become brittle and are in danger of being lost. Our collection at Mullen Library contains many ninteenth and early twentieth century books that are becoming brittle. The Collection Management Department makes important decisions about protecting, reformatting or replacing brittle books to ensure that these books will continue to be available to scholars.