The printing-frame is much like a book-printing frame, and is furnished inside with a second small frame which holds the paper, being furnished with small springs or strings. When the frame has been turned over the stone, the paper must be at least half an inch from the stone to avoid smutting, which will occur if it touches. The paper must not touch the stone till pressure is applied, and then only on the spot pressed downward by the scraper.
As soon as both parts of the scraper arm are in a straight line, so that they form practically one piece, the scraper wood is pulled down and the printer draws it toward himself over the printing-frame and the stone plate. At this time the following is to be observed:—
(1) Both parts of the arm must be so fastened to each other that they may be bent like a knee, but once they are straight in line, they must stay in that position. It is well, therefore, so to adjust the parts that they will not be directly over each other, but rather exceed a straight line under pressure, and bend a little inward. The position of the scraper must be considered also. On the whole the following rule holds good: the point where both parts are united with a nail or a screw must not be in a perfectly straight line between the point where the scraper rests and the point where the arm is fastened above, but should be at least two and a half inches forward of that point. Otherwise the arm may spring outwards toward the workman and injure him severely. The third illustration shows the construction of the scraper arm and the scraper.
(2) The arm must be grasped as low as possible when being drawn toward one's self, in order to diminish the danger of springing outward.
(3) The workman must press his body tightly to the table of the press to get proper leverage. Standing free, a man of moderate strength could not move the scraper at all when the pressure is on, but a man standing in correct position can do it without difficulty.
(4) Under very heavy pressure the inker-in, who stands on the other side of the press, can help by pushing.
The scraper is a piece of pear wood as long as the size of the plate demands. Its height is about four inches, its thickness one inch. The end that rests on the leather is trimmed down so that it has a thickness of only one line. This end must be especially true and planed to fit the stone, also neatly rounded off. It should be so fastened to the arm that it may be adjusted to the position of the stone. The stone does not always lie truly horizontal in the press, sometimes because it is not uniformly thick, sometimes because the underlay is not quite even, and sometimes because the press itself has been a little strained. If the scraper has been made properly, it will adjust itself to the stone, even if the scraper arm is not quite plumb on the stone, a condition that often occurs with small work, such as titles and other things that are at the end of a stone.
(5) For every press a number of scrapers of different dimensions must be in stock. Generally a lever press is so made that the printing-frame can be raised or lowered according to the thickness of the stone. Then the scraper must be changed accordingly.
(6) The connection of the upper board with the tread is made by a thin stick that is fastened to a lever below, by means of a small iron piece which contains several holes that serve to adjust the height of the tread according to need.
(7) The leather in the printing-frame is strong calfskin. It must be stretched very evenly and tensely and must be smeared from time to time very thoroughly with tallow.