CALENDERING (Fr. ralandre, roller, from Lat. cylindrus, Gk. KOXa3pos, kylindros, cylin der, roller). The term applied to the finishing process by which a glazed or polished surface is given to paper and various textile fabrics, such as linen and cotton. It is usually done by pass ing the fabric between cylinders or rolls under pressure, hence the origin of the term. which is a corruption of cylindering. The familiar do mestic process of starching and ironing illus trates in a simple form the object and result of calendering, and the common domestic mangle is a near approach in a simple form of the large calendering machines used in paper and textile manufacture. These machines consist of a series of from three to twelve rolls or 'howls' set one above the other in a strong iron frame and so arranged that heavy pressures can be brought to hear on the rolls, and, therefore, on the fabric which is passed between them. The rolls were formerly made of wood. hut this material proved unsatisfactory because it warped. At present, when metal rolls are not used, the rolls are made of paper or cotton rendered solid by hydraulic pressure. Metal rolls are made of steel. chilled cast iron, or brass, and are often made hollow, to allow them to be heated internally where hot calendering, is required. The process of ealender
ing consists in passing the fabric between the rolls a, number of times, depending upon the ma terial and the finish required. Often cloths are starched before being calendcred. To impart a. glaze or polish one of the pair of rolls is made to revolve faster than the other. which causes it to slide on the fabric, with exactly the same effect as results from the sliding back and forth of the flatiron in 'ironing' or polishing the domes tic linen. Sometimes the surfaces of the rolls have slightly raised patterns which produce the effect known as watering. In making the rolls for calendering the utmost accuracy of workman ship is exercised to secure a truly cylindrical surface; metal rolls are turned on a lathe, then ground and finally polished. Great care has also to be taken in setting the rolls in the frame and in adjustimg them to each other. The method of applying the pressure is by using weights or by hydraulic presses, or by means of screws, the former being preferable where heavy pressures are required. See BEETLING.