Calendering
Aiton's Encyclopedia (1910)
a mechanical process by which cotton and linen textiles are "finished," that is, given a smooth surface, and, if desired, a glaze. Three ends are to be attained by calendering. First, the fabric is to be made smooth, without fold or wrinkle. Second, the threads are to be compressed until they lose their round shape and become flat. Thus they are brought into closer contact and an appearance of strength and firmness is given to the fabric. At the same time all knots and lumps caused by imperfections in the thread are flattened and smoothed. The third purpose is to give a luster or glaze to the surface of certain materials. The agencies employed to accomplish these ends, are heat, moisture, pressure, and friction, exactly as in ordinary domestic ironing. The calendering machine contains from two to five cylinders, made of cast iron , wood, paper, or cotton, according to the purpose for which they are designed. These are so arranged that the pressure can be gauged as desired. To produce friction, the cylinders are geared to revolve at different rates of speed, so that they will rub the surfaces. A watered or moire' effect is produced by passing a double fold of material between the cylinders. The threads of one layer press upon the others, so that they are flattened in some places more than in others, and thus reflect the light differently. Sometimes the cylinders are engraved to produce regular moire' effects, or embossed designs, such as are seen on velvet. A machine arranged to calender fabrics while wet is used for coarse, heavy cloth, of hemp, jute, etc. It is called a water-mangle. The polish or finish of certain papers is produced by calendering.
What Has Changed in the Last Century
The mechanics Aiton's described in 1910 -- heat, moisture, pressure and friction between geared rolls turning at different speeds -- are still the mechanics of a calender today, and moire and embossing are still made much as the entry says. What has changed is what goes through the nip: since the 1930s and 40s calendering became a mainstay of the rubber and plastics industries, producing PVC film and sheet and coating tyre fabric, and today calender rolls also compact the coated electrodes of lithium-ion batteries to a specified density. In textiles the friction glaze Aiton's prized has largely given way to chemical resin finishes, while the roll materials have moved on from the wood and paper-filled cylinders of 1910 to steel, chilled iron and polymer-covered rolls, and paper mills use soft-nip calenders under computer-controlled loading rather than the older stacks alone.
Written for this edition, 2026.