The rollers should be kept clean, but should not be too moist, as this will prevent the ink from distributing equally over them, and from covering evenly the surface of the types or engraving; nor should they be too dry, as in that case they will not dispose of the ink smoothly enough to produce a fine impression, neither will they retain particles of dirt on their surface, but it will part with them to the form, thus causing picks.
The ink ought to be rubbed out thinly and equally on the ink-block, so that when it is taken it may be diffused smoothly over the surface of the rollers. It is advisable to keep rubbing the ink out on the block with the brayer, and to distribute the roller almost constantly; the continual friction produces a small degree of warmth, which is of advantage, particularly in cold weather.
As uniformity of colour is requisite for beauty in printing, where the form is large the pressman should take ink for every impression: this may be thought troublesome, but it is advantageous in producing regularity of colour. It is unpleasant to see in a fine book two pages that face each other differing in colour,—the one a full black, surcharged with ink, the other deficient in quantity and of a gray colour; yet this must happen when, as is frequently the case, three or four sheets are printed with one taking of ink.
In fine books, particularly where the paper is large and heavy and the type large, set-off sheets are used to interleave the whole impression while working: these remain till the printed paper is taken down from the poles by the warehouseman. These set-off sheets are put in when the white paper is working, and moved from one heap to the other during the working of the reiteration. They prevent the ink from setting off from one sheet to another while they are newly printed, from the weight of the paper.
To secure uniformity of impression, the pull should be so adjusted in the first instance as to give a proper degree of pressure on the form when the bar is pulled home; then, checking the bar, it should be allowed to rest in that position during a short pause.
It will be perceived that, to produce presswork of a highly superior character, great expense and much time are required; and that it is requisite to have a good press in good condition; to have new types, or types whose faces are not rounded by wear; to have good rollers in good condition; that the ink should be strong, of a full black colour, that it will not fade nor stain the paper, and ground so fine as to be impalpable; the paper should be of the best quality, made of linen rags, and not bleached by means of acids or bleaching powders, which have a tendency to decompose the ink; the rolling should be carefully and well done; the face of the type should be completely covered with ink, without any superfluity, so as to produce a full colour; and the pull should be so regulated as to have a slow and great pressure, and to pause at its maximum in order to fix the ink firmly upon the paper. These particulars observed, with nothing but paper in the tympans, perfect impressions of the face alone of the type will be obtained, and a splendid book will be produced in the best style of printing.[20]
PRINTING WOOD-CUTS.
A single block, when imposed in a large chase, may spring out of the chase while being inked, from the quantity of furniture about it. A good plan is to impose it in a job-chase, and to impose this chase in a larger one: this will cause it to lie flatter on the press and firmer in the rolling, the large chase being secured firmly on the press by quoins and the corner irons.
Before pulling the first impression, the workman should see that the surface of the cut is perfectly clear from particles of dirt, and that no pin or lump of paste is on the tympan. He ought then to pull very gently, or he may injure some of the fine lines of the engraving.