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The calender is a series of hard pressure rollers at the end of a papermaking
Papermaking

Papermaking is the process of making paper, a substance which is used ubiquitously today for writing and packaging.In papermaking a dilute suspension of fibers in water is drained through a screen, so that a mat of randomly interwoven fibers is laid down....
 process (on-line). Those that are used separate from the process (off-line) are also called "supercalenders". The purpose of a calender is to smooth out the paper
Paper

Paper is thin material mainly used for writing upon, printing upon or packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....
 for printing
Printing

Printing is a process for reproducing text and image, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing....
 and writing
Writing

Writing is the representation of language in a textual Media through the use of a set of signs or symbols . It is distinguished from illustration, such as cave drawing and painting, and the recording of language via a non-textual medium such as Magnetic tape sound recording....
 on it, and to increase the gloss on the surface.

The word “calender” itself is a derivation of the word kylindros, the Greek word for “cylinder”.

In the past, the paper sheets were worked on with a polished hammer
Hammer

A hammer is a tool meant to deliver an impact to an object. The most common uses are for driving Nail s, fitting parts, and breaking up objects....
 or pressed between polished metal
Metal

In chemistry, a metal is a chemical element whose atoms readily lose electrons to form positive ions , and form metallic bonds between other metal atoms and ionic bonds between nonmetal atoms....
 sheets in a press.






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The calender is a series of hard pressure rollers at the end of a papermaking
Papermaking

Papermaking is the process of making paper, a substance which is used ubiquitously today for writing and packaging.In papermaking a dilute suspension of fibers in water is drained through a screen, so that a mat of randomly interwoven fibers is laid down....
 process (on-line). Those that are used separate from the process (off-line) are also called "supercalenders". The purpose of a calender is to smooth out the paper
Paper

Paper is thin material mainly used for writing upon, printing upon or packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....
 for printing
Printing

Printing is a process for reproducing text and image, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing....
 and writing
Writing

Writing is the representation of language in a textual Media through the use of a set of signs or symbols . It is distinguished from illustration, such as cave drawing and painting, and the recording of language via a non-textual medium such as Magnetic tape sound recording....
 on it, and to increase the gloss on the surface.

The word “calender” itself is a derivation of the word kylindros, the Greek word for “cylinder”.

In the past, the paper sheets were worked on with a polished hammer
Hammer

A hammer is a tool meant to deliver an impact to an object. The most common uses are for driving Nail s, fitting parts, and breaking up objects....
 or pressed between polished metal
Metal

In chemistry, a metal is a chemical element whose atoms readily lose electrons to form positive ions , and form metallic bonds between other metal atoms and ionic bonds between nonmetal atoms....
 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 ). The pressure between the rollers, the "nip pressure", can be reduced by heating the rolls and/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
Cast iron

Cast iron usually refers to Gray iron, but also identifies a large group of ferrous alloys, which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy....
 or steel
Steel

Steel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.14% by weight , depending on grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese, chromium, vanadium, and tungsten....
, and “soft” rollers coated with polymeric composites. This widens the working nip and distributes the specific pressure on the paper more evenly.

Other materials

Calenders can also be applied to materials other than paper when a smooth, flat surface is desirable, such as cotton, linens, silks, and various man-made fabrics and polymers such as vinyl
Vinyl

A vinyl compound is any organic compound that contains a vinyl group , −CarbonHydrogenCovalent bondCH2. These are derivatives of ethene, CH2=CH2, with one hydrogen atom replaced with some other group....
 and ABS
Acrylonitrile butadiene styrene

Acrylonitrile butadiene styrene is a common thermoplastic used to make light, rigid, molded products such as piping , musical instruments , golf club heads , automotive body parts, wheel covers, enclosures, protective head gear, airsoft Airsoft gun and toys, including Lego bricks....
 polymer sheets, and to a lesser extent HDPE, polypropylene
Polypropylene

Polypropylene or polypropene is a thermoplastic polymer, made by the chemical industry and used in a wide variety of applications, including packaging, textiles , stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknotes....
 and polystyrene
Polystyrene

Polystyrene , sometimes abbreviated PS, is an Aromaticity polymer made from the aromatic monomer styrene, a liquid hydrocarbon that is commercially manufactured from petroleum by the chemical industry....
.