Methods of Printing

Machines for peg or surface printing, as it is sometimes termed, are arranged much in the same way as intaglio printing machines, except that the peg or printing roller is cut in relief and the colour is served to it by means of a short endless colour blanket or sleeve which is supplied from colour furnishing rollers. It is usually employed for rather large designs on cheap cretonnes and linoleum.

Roller Printing or Cylinder Printing.

The working of the machine is shown in fig. 3. A cast iron cylinder is mounted by means of pins, at each corner of the block, which are arranged so that, when those at the right side or at the top of the block fall upon those at the left side or the bottom of the previous impression, two printings join up exactly and continue the pattern without a break. As each length is finished it is wound over the drying rollers, thus bringing forward a fresh length to be treated similarly. If the pattern contains several colours the cloth is usually first printed throughout with one, then dried, re wound and printed in turn with the others.

Many modifications of block-printing have been tried from in adjustable bearings capable of sliding up and down slots in the sides of rigid iron framework. It is covered with several folds of lapping and a blanket of wool or rubber to give elasticity. Beneath is an engraved copper roller which is supplied with colour from a roller which revolves in a colour box below it. Two knives known as "doctors" rest against the engraved roller, one serving to remove colour from the smooth parts of the roller and known as the "cleaning doctor." It is pressed against the roller by means of levers. The other, made of brass, is the "lint doctor" which removes loose filaments or lint which the roller picks up from the cloth.

In operation, the cylinder is screwed down with an even pressure into frictional contact with the roller below; the machine is then set in motion, turning in the direction indicated by the arrows ; the cloth is now introduced between them and as it leaves the machine fully printed it is carried over a series of drying chambers situated above and heated by steam. The printing roller is the only part of the machine directly con nected with the motor or main drive of the works through the cog-wheel on its axle—the "mandril"—all the other parts de riving their motion from it, either by friction as in the case of the cylinder or by a spur wheel as in that of the colour-f urnish ing roller. The mode of printing is almost self-evident ; the roller revolving in the direction of the arrow takes colour from the "furnisher"; the excess is then scraped off by the "doctor" 'and, in continuing on its course, it comes in contact with the cloth which being pressed by the cylinder into the engraving ab stracts the colour therefrom and of course receives an exact im pression of the engraved pattern. The pressure may be applied

either through the cylinder to the roller or from the engraved roller to the cylinder by compound levers.

Larger machines printing from two to 16 colours are precisely similar in principle to the above, but differ somewhat in detail and are naturally more complex and difficult to operate. In a 12 colour machine (fig. 4) for example, 12 copper rollers, each carrying one portion of the design, are arranged round a central pressure cylinder, or bowl, common to all, and each roller is driven by a common driving wheel, called the "crown" wheel, actuated, in most cases, by its own steam-engine or motor. The pressure is applied to the cylinder through the rollers which work in specially constructed bearings capable of the following move ments: (I) Of being screwed up bodily until the rollers are lightly pressed against the central bowl; (2) of being moved to and fro sideways so that the rollers may be laterally adjusted; and (3) of being moved up or down for the purpose of adjusting the rollers in a vertical direction. Notwithstanding the great lati tude of movement thus provided each roller is furnished with a "box-wheel," which serves the double purpose of connecting or gearing it to the driving wheel, and of affording a fine adjustment. Each roller is further furnished with its own colour-box and doctors.

In recent years many improvements and additions have been made in printing machines. Chief amongst these are those em bodied in the "intermittent" and the "duplex" machines. In the former any or all of the rollers may be moved out of contact with the cylinder at will, and at certain intervals. Such machines are used in the printing of shawls and "saris" for the Indian mar ket. The goods require a wide border right across, and it is to effect this, with rollers of ordinary dimensions, that "intermittent" machines are used. The body of the "saris" will be printed, say for six yards, with eight rollers ; these then drop away from the cloth and others, which have up to then been out of action, immediately fall into contact and print a border or "crossbar" say one yard wide, across the piece ; they then recede from the cloth and the first eight again return and print another six yards, and so on continually.