PRINTING PRESS, COPPERPLATE. The invention of the copperplate printing press seems to have been made about the same period as the type printing press. In the bsence of authentic record, tradition has ascribed the discovery to a silver-smith, who, in order to save labour, and ensure the accurate and rapid multiplication of engrav ed patterns upon his works, was in the habit of inking in the pattern, and taking off impressions with a burnisher from the figure first executed. This is so simple, and generally so well understood a process, that we need not waste time in describing it.
The success attending this discovery, immediately sug gested that the same results would be obtained in a more perfect manner, by a proper application of the pressure of a roller to the whole surface of the plate at once, instead of the labour of passing the burnisher in the hand gradually over each individual spot of engraving. The first invented presses appear to have been constructed with considerable accuracy and power from the excellence of the impres sions of the ancient works which have reached us, but which it would be out of place to enumerate here.
In the present age of improvement and novelty, many alterations, and certainly great amendments have been made, both upon the construction of the press for the higher branches of printing, and also upon that adapted to more ordinary purposes. Among the most prominent of these improvements is the application of the wheel and pinion, instead of the lever or cross for driving the press, and the substitution of cast iron in place of wooden rollers. Other plans have been suggested for the purpose of in creasing the rapidity of multiplying the impressions of common-place works, the most ingenious of which is the invention of the celebrated Mr. Perkins, and of which a complete account will be found in the London Journal of the Arts, No. III. Plate VIII. Figs. S and 4. We shall describe these presses after we have detailed the construc tion of the more simple machinery ; but before proceeding, it may not be out of place to remark, that the principal re quisites of a good copperplate press are perfect truth in the manufacture of the rollers and plank interposed be tween them, and the judicious application of such a work ing power as shall cause the least bodily fatigue to the printer. If the workman has to apply too much of his strength to drive the machinery, his hand will be made to shake in consequence of the exertion, and thus he will be rendered incapable of cleaning off the ink from the plate, with that delicacy of touch which is indispensably requisite in finer works. The printers of calico goods, aware of the importance of this consideration, have skilfully applied the power of the steam engine for this purpose ; and we have been informed that the presses in the bank of Ireland for printing their notes, are also driven by the same means.
Fig. I 1, Plate CCCCLXIII. represents the most simple copperplate press, which, with the exception of the spindles of the two rollers, may be entirely constructed of wood. A is the upper roller, B the under roller, a little larger in the diameter than the upper ; C the plank upon which the copperplate P rests. The plate should be placed upon a piece of pasteboard of a little longer size than the paper upon which the impression is to be taken, in order to defend the plank against the indentation consequent on the necessary pressure of the roller. D is the strongest part of the frame of the press, commonly called the cheeks ; d an open space in the cheeks for admitting the axes or spindles of the rollers. The upper roller has a brass bush fitted to the upper half of the spindle, and upon which is placed a proper quantity of pieces of pasteboard and felting in alternate layers, in order to give elasticity to the pressure, and greater ease to the workman. The spindle of the under roller is also placed in a brass bush, sometimes with, but oftener without, a mass of elastic substance. In this opening two screws are fixed, so as to act upon the elastic mass placed above the spindles of the upper roller, for the purpose of regulating the pressure necessary to produce the requisite boldness of the impression. Some skill is required in the management of these screws, for we have seen that strength of body, without this knowledge, has actually broken the spindles of the rollers in vain attempts to perform what a judicious workman would accomplish with comparative ease. In order to keep the elastic mass above described as efficient as possible, it should be taken out at night, turned, and replaced in the morning. Much of the excellence of the work also depends upon the proper quantity of felting or cloth being warped round the upper roller b b. If too many layers are put on it, the result will be, that greater power will be required to drive the press, and the impression will not be so clear and distinct as it ought ; and again, if too few layers of cloth are applied, the paper will be stained by the hardness of the roller, and it will have a glazed appearance, and be liable to be cut by the edges ol the copperplate. These defects also result (though in a less degree) from the want of a proper quantity of the elastic ma s being placed above the spindle of the upper E is the remaining part of the frame of the press, and F the levers or cross fixed to the end of the spindle by which the motion is given to the upper, and communicated to the under roller.