Watermark

A watermark is an identifying image or pattern in paper that appears as various shades of lightness/darkness when viewed by transmitted light (or when viewed by reflected light, atop a dark background), caused by thickness or density variations in the paper. Watermarks have been traceable for handmade paper since the 13th century, originally serving as trademarks of the manufacturing paper mills. Since the screens for paper production only had a limited service life and paper was usually not stored for long due to its high price, it is possible to date historical papers very precisely by determining datable watermarks and comparing them with the deviations caused by the manufacturing process. For this reason, filigranology (watermarking) has established itself as a forensic auxiliary science for historical sciences, especially in art history, to determine the age, origin and authenticity of documents and graphic works of art using watermarks. For this purpose, extensive historical collections have been created since the beginning of the 20th century, many of which are now available as databases. Watermarks on papers that have been damaged, poorly preserved or extensively painted over can also be made visible again with the help of modern analysis methods such as multispectral photography. Nowadays, watermarks are mainly used as security features on bank notes, postage stamps, and other government documents to discourage counterfeiting. In the course of digitization, however, imperceptible markings and information in media files that can only be detected with certain methods are referred to as “digital watermarks”. As with traditional watermarks, the document and watermark information should be inextricably linked. There is a separate process for each type of media (images, audio, video), which is adapted to the respective coding and data format. At book2net, too, we offer special software modules to protect digital copies with individual digital watermarks.