The illustration serves to convey an idea of this which is termed press print ing.
The cylinder printing machine con sists of an engraved copper cylinder, so mounted as to revolve against another cylinder lapped in 'woollen cloth, and imbued with a colored paste, from which it derives the means of giving colored impressions to pieces of cotton passed over it. The cylinder as it rotates dips in a long trough of color, and every part of it becomes coated. The excess of color has to be removed from the sur face of the cylinder with a knife : this is called doctoring. The cloth then passes in a continuous strip between the cylin der and a large roller or drum above, by which it is pressed close so as to imbibe the color from the sunken device on its surface. As the cylinder is continually revolving while the cloth passes, the printing goes on uninterruptedly with out stoppage or break. When a ma chine prints several colors, there are as many cylinders as colors required, each having a trough and doctor of its own, and the cloth passes in contact with each in turn.
Each cylinder machine prints a piece (23 yards) of cloth in a minute and a quarter, or three quarters of a mile per hour. In the subjoined illustration the cloth may be seen traversing the cylinder.
The economy of cylinder printing is very great. One machine with a man, and a boy to tend the color trough, being capable of printing as many pieces as 200 men and boys could do with blocks. A modification of cylinder printing is with wooden rollers cat in relief; it is called surface printing, the thick hoin first laid on a tense woollen surface, and then transferred to the cylinder. When copper and wooden cylinders are com bined in one appara tus, it has gotten the name of union print ing. Having alluded to the mechanical operations, those Which are chemical require now to be noticed.
If one hundred patterns of cotton re quire to be printed, nearly one hundred different modes of proceeding are ne cessary in the print ing; for not only must the colors be different, but each color may perhaps require a peculiar Froundwork to make it adhere to the cloth. Herein lie the delicacy and com plexity of the calico printer's operations ; and hence arises a different chemical formula for almost every different pat tern. Sometimes a piece of cloth is par tially printed, then dye.] and then printed again ; ' at other times the printing is effected at once ; and at others a portion of the printing is to lay on color which is to be afterwards while the other por tion is merely to imprint the cloth with a chemical agent which shall exert some peculiar effect on the colors. This may
perhaps be rendered intelligible by al to four different kinds of liquids or mixtures which are printed on the cloth by means of the cylinder, the press, or the block. These four are colors, mordants, dischargers, and resists. The name colors speaks for itself; it relates to the pigments or pastes which impart color to the cloth, and includes a very wide range of vegetable and mineral substances. A mordant is a liquid mix ture which enables the coloring sub stance to combine permanently with the textile fibre ; and this is used when the mordant has a combining affinity with the cloth as well as with the color, al though the two latter, used singly, have no affinity for each other. Thus, if a red color were imparted to cloth by mad der, it would wash out, or not be a "fast ta,lor ;" but if the cloth were previously netted with an aluminous salt, the mad der color would be permanent. In most cases the mordant is a body of liquid, into which the cloth is immersed ; but sometimes it is used in the same way as a paint or ink by the cylinder-machine. Dischargers, instead of being intended to fix the color to the cloth, are used to drive off or discharge the color after the latter is applied. This kind of chemical agent is used in combination with mor dants, thus : the cloth is wholly satu rated with the mordant, but certain parts are also printed with a discharger formed cf lemon-juice or some other substance ; the result of which is, that when the dye-color is afterwards applied, it com bines with the cloth at the parts where the mordant has been unaffected, but becomes a "loose" color at the parts printed with the discharger, so as to be easily washed out from those parts. Re sists are mixtures which enable the printer to produce white portions ofpat tern by a process rather different from the discharge-method. The mordant is printed, not dipped, in those parts which are to be colored in the pattern ; while those which are to be kept white are previously printed with a mixture called. a resist or resist-paste. The cloth is then wholly immersed in a dye-vat, but those portions which had been printed with the resist refuse to receive the dye, and hence remain white. It will be seen, therefore, that in " discharge work," as it is called, the white portions are re tained by driving out the mordant, which would. otherwise fix the color ; while in "resist-work" the white portions are re tained by shielding the cloth at those parts from the action of the color.