What is "calendering"

Calender \Cal"en*der\, v. i. [imp. & p. p. Calendered; p. pr. & vb. n. Calendering.] [Cf. F. calandrer. See Calender, n.] To press between rollers for the purpose of making smooth and glossy, or wavy, as woolen and silk stuffs, linens, paper, etc.
--Ure.

vb. (present participle of calender English)

Calendering is a finishing process used on cloth, paper, or plastic film. A calender is employed, usually to smooth, coat, or thin a material.

With textiles, fabric is passed under rollers at high temperatures and pressures. Calendering is used on fabrics such as moire to produce its watered effect and also on cambric and some types of sateens.

In preparation for calendering, the fabric is folded lengthwise with the front side, or face, inside, and stitched together along the edges. The fabric can be folded together at full width, however this is not done as often as it is more difficult. The fabric is then run through rollers that polish the surface and make the fabric smoother and more lustrous. High temperatures and pressure are used as well. Fabrics that go through the calendering process feel thin, glossy and papery.

The wash durability of a calendared finish on thermoplastic fibres like polyester is higher than on cellulosic fibres such as cotton. On blended fabrics such as Polyester/Cotton the durability depends largely on the proportion of synthetic fibre component present as well as the amount and type of finishing additives used and the machinery and process conditions employed.