Printing and bookbinding for schools

by Samuel Jesse Vaughn

Fig. 26.

The first thing in the matter of handling a press, Fig. 26, is to have a clear idea in mind as to the method of its operation; the next is to make sure that the press is well oiled, well cleaned and the bed and platen clean of all grit, paper, gauge pins, quadrats, etc.

The throw off, a, Fig. 26, is a lever by use of which the press can be prevented from printing. This should always be in such position as to hold the platen, b, away from the bed, c, until the press is ready for an impression.

An essential part of the press which needs to be mentioned separately is the rollers, d.

They are a kind of rubbery composition moulded around steel rods or cores; and when placed on the press, they distribute the ink over the plate, e, and carry it down upon the type. Of course, they are soft and pliable and need proper attention to keep them so. There are summer rollers and winter rollers and neither can be used to advantage out of season. Winter rollers become too soft for summer, while the reverse is true of summer rollers used in winter. Seventy degrees is about the right temperature to insure the proper working of rollers. When they become permanently hard enough to retain, for a considerable time, the type impressions, rollers are said to be dead. Much can be told about rollers by observing the color and the shine of the surface. A dead roller has a dead, lusterless surface. When rollers are worn out, they are simply sent to the factory where the old composition is removed and new composition molded upon the same cores. The chief constituents of rollers are molasses, glycerine and glue.

Make-ready. In preparing the make-ready, a hard surfaced piece of pressboard is placed on the platen. On top of this, should be from three to five pieces of book paper for “packing,” covered finally with a “drawsheet” of tough manila. Now the press is inked by putting upon the plate, e, a small quantity of ink and allowing the press to run until the rollers have thoroughly distributed it over the plate. Then the form is put into the press at c, and care is used to see that the grippers, f, are properly adjusted so that they do not strike the form and at the same time, are not far enough out to strike the roller supporters. In case of interference of grippers, one or both may be removed. When everything is ready, an impression is taken on the draw sheet and is examined to see if any type are high, or to discover and correct any other defect. Then the lower clamp, g, is loosened and while the draw sheet is thrown back, an impression is taken on the top sheet of the packing. If a portion of the impression is indistinct, a thin piece of paper is pasted upon the indistinct parts to give them a slightly heavier impression. This is known as the overlay. In patching up the make-ready in this manner, it is very important that the overlay shall not reach beyond the parts which need building up. If an indistinctness in an impression is due to worn type or a low cut, it may be remedied by an underlay. This is the pasting of bits of paper or cardboard to the foot of the type, or to the back of the cut. In case a portion shows too heavy an impression, that particular part is cut out of the top sheet of the packing. Then the draw sheet is clamped down again and a device is arranged for holding the stock for printing.

Fig. 27.

For locating the positions of the gauge pins, Fig. 27, or quadrats, the stock is laid straight across the impression allowing the ends to project equally over the ends of the impression, and with a sharp pencil, a mark is made on the draw sheet along the left end of the stock. Then the stock is slipped down across the impression in such a way as to allow the edges of the stock to project the distance of the desired margins above and below the impression on the drawsheet. A mark is then placed along the lower edge of the stock. The gauge pins or quads are placed on these two lines, two on the horizontal and one on the vertical, in such a position as will best hold the stock on the platen. If quads are used, they are glued to the drawsheet. It usually takes several impressions on the cut stock to get a perfect adjustment. In order to prevent the stock from being lifted from the platen by the ink, a small cord is tied about the ends of the grippers in such a position as that it strikes the stock above the impression of the type.

Constant care must be exercised to keep the grippers from getting in the way of the roller supporters and causing considerable injury.