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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
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