Editing Calender (section)

==History==
Calender mills for pressing [[Serge (fabric)|serge]] were apparently introduced to the Netherlands by Flemish refugees from the [[Eighty Years' War]] in the 16th and 17th centuries.<ref>{{cite journal |last1=Van Uytven |first1=R. |title=The Fulling Mill: Dynamic of the Revolution in Industrial Attitudes |journal=Acta Historiae Neerlandica |date=1971 |volume=V |page=12}}</ref>

In eighteenth century China, workers called "calenderers" in the silk- and cotton-cloth trades used heavy rollers to press and finish cloth.

In 1836, Edwin M. Chaffee, of the Roxbury India Rubber Company, patented a four-roll calender to make rubber sheet.<ref name=Polymers>{{cite book|last1=White|first1=James Lindsay|title=Principles of Polymer Engineering Rheology|date=July 20, 1990|publisher=Wiley-Interscience|page=49|isbn=9780471853626|url=https://books.google.com/books?id=q9X5C_0kpgIC&pg=PA49|access-date=2014-12-25}}</ref> Chaffee worked with [[Charles Goodyear]] with the intention to "produce a sheet of rubber laminated to a fabric base".<ref name=Plastics>{{cite book|last1=Simpson|first1=W. G.|title=Plastics: Surface and Finish|date=December 31, 1995|publisher=Royal Society of Chemistry|page=52|isbn=9780854045167|url=https://books.google.com/books?id=BUipGAKOh3gC&pg=PA52|access-date=2014-12-25}}</ref> Calenders were also used for paper and fabrics long before later applications for thermoplastics. With the expansion of the rubber industry the design of calenders grew as well, so when PVC was introduced the machinery was already capable of processing it into film.<ref name="Plastics"/> As recorded in an overview on the history of the development of calenders, "There was development in both Germany and the United States and probably the first successful calendering of PVC was in 1935 in Germany, where in the previous year the Hermann Berstorff Company of Hannover designed the first calender specifically to process this plastic".<ref name="Plastics"/>

In the past, for paper, sheets were worked on with a polished [[hammer]] or pressed between polished [[metal]] sheets in a press. With the continuously operating paper machine it became part of the process of rolling the paper (in this case also called web paper).<ref>{{Cite web |url=http://glossary.ippaper.com/default.asp?req=glossary%2Fterm%2F2525&catitemid= |title=International Paper - Web Paper |access-date=2018-11-17 |archive-url=https://web.archive.org/web/20090410031409/http://glossary.ippaper.com/default.asp?req=glossary%2Fterm%2F2525&catitemid= |archive-date=2009-04-10 |url-status=dead }}</ref> The pressure between the rollers, the "nip pressure", can be reduced by heating the rolls or moistening the paper surface. This helps to keep the bulk and the stiffness of the web paper which is beneficial for its later use.

Modern calenders have hard heated rollers made from chilled [[cast iron]] or [[steel]], and soft rollers coated with [[polymeric]] composites. The soft roller is slightly non-cylindrical, tapered in diameter toward both ends, to widen the working nip and distribute the specific pressure on the paper more evenly.