Calendering (Fr. calandre, from Gr. cylinder), the process of finishing cotton and linen goods by passing the cloth between smooth cylinders, which are made to revolve in contact. The term also includes the subsequent operations of cloth-lapping, or folding the cloth, and packing and shipping it, which operations are performed in the same establishment. Paper is also subjected to the finishing process of calendering. The name calender is applied to the machine comprising the rollers which smooth the woven fabrics. Before passing the cloth between them, it is essential that such as is designed for calico printing should be subjected to the singeing process, in order to remove the loose fibres or down. It consists in drawing the cloth rapidly over a horizontal gas pipe, along which numerous little apertures extend in a straight line, so that the gas, ignited, gives a line of flame equal in length to the width of the cloth. Another pipe, placed over this and exhausted of air, draws in the flame through the goods as they pass between the two pipes, and the loose fibres are burned out without igniting the fabric. The movement is. at the rate of about three feet in a second.
Any sparks that may remain are extinguished as the cloth immediately passes between two rubbers placed in front of the line of flame. A yellow color like that of nankeen is produced by this process, which requires to be removed by bleaching, before printing. As the goods are received by the calender, they are commonly first dampened, whereby the folds and creases are partially removed, and the cloth is better prepared for the succeeding operation. The objects to be attained in calendering are, rendering the surface of the fabric smooth and even by the removal of all wrinkles, the flattening down of all knots and other imperfections, and the spreading of the threads so as to give them a flattened form, and the texture the appearance of closeness and strength. The polish upon cotton goods, called glazing, is produced by the friction they receive in this process. Lawns and muslins of light texture are smoothed in light machines not heated, and with moderate pressure, there being no objection to their threads retaining the cylindrical form, and the fabric its open texture.
Fabrics which are to go to the calico printer require a high pressure, and sometimes to be passed twice through the rollers; but those which have already been partially colored, and are to be filled in with other colors, must not receive that stiffness of finish which would prevent the cloth being stretched one way or the other, whenever it may require slight changes of form, to admit of the exact adjustment of the grounding blocks to the outlines of the colors already applied. - The smoothing calender was introduced into Great Britain from Flanders and Holland during the persecution of the Huguenots. It has been improved by substituting rollers made of pasteboard disks for three of the five commonly employed in the machine, which three were previously constructed of wood, and were consequently liable to warp and crack with the heat to which they were exposed. The other two are hollow cylinders of cast iron, constructed of metal 2 in. thick surrounding the internal cavity of 4 in. diameter; this gives them a diameter of 8 in. The cavity admits of the introduction of a red-hot roller or of steam. The pasteboard cylinders suitable for the iron ones of the dimensions given are two of 20 in. diameter, and two of 14 inches.
They are placed in a strong upright iron frame, the small cylinder in the middle and an iron one above and below it, revolving as a cylindrical smoothing iron between the two pasteboard cylinders, which take the place of the domestic ironing board or table with its cover of cloth. The paper rollers are contrived so as to avoid the defects of the wooden ones, and present a smooth surface to the cloth. Set like a wheel upon its axle, a disk of cast iron at the end of a strong iron bar is perforated with six holes near its circumference for as many iron rods to pass through. Circular plates of thick pasteboard, an inch larger in diameter than the intended roller, are next laid upon this disk; they are furnished with holes for the axle and the iron rods. The pile is continued to a length as much exceeding that intended for the roller as the pasteboard disks will shrink by the compression they will be subjected to. A corresponding iron plate is then set upon the other end of the axle, and the rods being passed through and screwed up, the cylinder thus formed is put in a hot apartment or stove to be thoroughly dried for several days, the screws being occasionally tightened upon the rods as the pasteboard shrinks. The surface of the cylinder thus obtained is very hard and close.
To turn it down to its proper size is a work of great labor, and the best tools are rapidly dulled. They are necessarily of small size, slowly working down the face of the cylinder, as it revolves at the rate of only 40 or 50 revolutions per minute. When finished, it presents a hardness and polish far superior to that of wood; it also possesses great strength, without the liability of being warped or injured by the great heat to which it is to be exposed. When set in the frame, they are so arranged that they may be forced by levers or screws into very close contact with the iron cylinders.
The cloth, fed from a roll placed opposite the machine, is carried over the upper pasteboard cylinder, between this and the iron one, then between this and the next below, and so on till it has been four times compressed and ironed. The glazing or polishing of the surface is produced by the middle pasteboard cylinder being made to revolve more slowly than the others, and consequently producing a rubbing effect of the cylinders upon the cloth. By this arrangement the former tedious operation of glazing upon a table is rendered unnecessary. A calender contrived by Mr. Dollfus has cylinders of sufficient length to pass through two pieces of cloth at once, and it is also provided with a folding machine, which receives the cloth as it comes out of the rollers, and folds it without the attention of the workmen. By running through two layers of cloth together, one upon the other, the threads of one make an impression upon the other, giving a wiry appearance to the surface. The embossed appearance is produced by rollers of copper, upon the face of which the design is engraved. - The proper folding of the cloth preparatory to its being pressed must, like the other operations of calendering, be carefully conducted, that the appearance of the finished article shall be free from creases and blemishes.
When the folds are completed, the pieces are placed, with thin boards and glazed pasteboard between each, in a powerful hydraulic press. While in the press the parcels are corded and prepared for packing in bales. The measure of the cloth has been taken before the folding, either upon the long measuring table, or by folding the cloth from one side to the other and back upon a graduated hooking frame, provided with two needles upon which each fold is suspended.