Dandy

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Egoutteur in the German Museum of Technology in Berlin

A dandy roll (also: dandy roll or forming roll ) is in the production of paper a light, with copper - or bronze wire -covered roller , which on the not yet solidified paper web (in the paper machine rolls). This feed roller in the paper machine is used to improve the paper structure and also to produce watermarks . The watermarks are created with applied figurative elevations or depressions - by displacement or accumulation of material. The contours of the watermark are highlighted negatively in the paper. If the dandy roll is smooth, the result is the unripped vellum paper .

background

Originally, the dandy roll was ( English : 'dandy roll') merely as Glättinstrument for rough paper tops on Fourdrinier machines used (introduction by John Marshall, London 1826). The function as a structuring or drawing element was only added in later years. The dandy roller's place of use is the wire section shortly before the suction cups or shortly after the first suction cups. It is crucial for the success of this technology that the paper web is thick enough, is already slightly solidified on the wire and is still liquid on the upper side. If the dandy roll is put on too early, the watermark will run out again. If it sits too far on the couch, it no longer displaces the fiber properly. The watermark will then become flat and fuzzy. The dandy roll is not driven and only runs at web speed due to the wire friction. Dandy watermarks are always (real) displacement watermarks. Coverings with plastic or stainless steel wire or mesh are also common. The leading dandy roll manufacturer in Germany has been the Kufferath company for years .

With the renewed use of duo and combination formers (Fourdrinier / suction goutteur or Fourdrinier / round sieve), new technologies are constantly being used that displace the classic Fourdrinier goutteur.

A special type of dandy roll is the dandy roll on the cylinder mold. It is the only form of application that results in a double-sided indentation in the paper (screen side with attachment watermark, top side with displacement watermark). Such dandy rolls are only known from the manufacture of securities and money.

variation

The molette watermark is generated by a steel roller covered with a rubber sheet in the wet end of a paper machine. It does not achieve the sharpness of the contours like the dandy roll, but is created in a similar way.

literature

  • Wisso Weiß: On the origins and development history of the dandy roll. In: IPH-Yearbook , Vol. 1, 1980, pp. 25-36.
  • Wilhelm Kufferath: Theory and practice of making watermarks with the dandy roll. In: Wochenblatt für Papierfabrikation , Vol. 98, 1970, No. 7, pp. 329–333; No. 8, pp. 355-358; No. 9, pp. 393-401; No. 10, pp. 431-440; No. 13, pp. 614-616.

Web links

Individual evidence

  1. ^ Richard Leslie Hills: Papermaking in Britain 1488-1988: A Short History. Bloomsbury Publishing, 2015, ISBN 978-1-4742-4127-4 (Reprint), pp. 43, 177 ff.
  2. ↑ See Wisso Weiß: Watermarks in machine paper . In: Jahrbuch der Deutsche Bücherei , Vol. 2, 1966, pp. 93–111.
  3. ↑ Cf. Frieder Schmidt: Machine paper watermarks in the collections of the German Museum of Books and Writing. In: Dialogue with Libraries. H. 1, 2011, pp. 62-66 or online version .