In former times inks were prepared by individual scribes using metal salts and tannic acids. These substances contained within the ink cause a hydrolytic splitting and/or oxidizing decomposition of cellulose fibres. In such cases, the paper remains completely intact in the non-written areas, but in the written passages the paper breaks up at the slightest touch. The illustration shows an 18th century manuscript of paper made with rags.

Photo: University Library, Graz