THINNING

Thinning occurs when paper is damaged by removing a layer of the fibers that make up the paper. This can occur to any part of a book or paper item, and may cause portions of a text to be unreadable.

In the first example, a sticker has been removed roughly with resulting loss to a layer of the cover. In the second example, a newsletter stuck to another document resulting in damage seen at the top of the page.