It is a matter of convenience to cast the "risers" or movable blocks for mounting plates, on the premises. They are usually made square, with indentations at the sides for reception of the brass catches, as in Fig. 177, which measures 3 in. long and l 1/2 in. square, other sizes being also made. The side clumps, Fig. 178, are made either 1 1/2 or 3 in. long, and 1 pica thick. The Fig. 177. blocks should be cast hollow to save metal. The catches, Fig. 179, are made of brass rule, and can easily be produced on the premises, by getting long strips cast with the required flange, then cutting up as needed, filing quite smooth, and drilling the necessary holes for admitting the pin that holds all secure.
After all the preceding processes, the plate is very carefully inspected for minor imperfections. Of course, anything like a serious imperfection is quite sufficient to condemn the plate entirely, and necessitate its being redone from the beginning; but small matters may be remedied. Among these are spots where the metal in the "whites" comes too high and would be in danger of taking the ink in printing; such must be chipped away with a sharp chisel. Again, individual letters may be battered; these require to be drilled out, a new type letter being dropped into the hole thus made, and secured by soldering from the back.
Before taking a cast from a stereotype plate, its type surface must be very thoroughly cleaned with a brush and some strong soda solution, as for washing ordinary type, to remove accumulated dirt. It is then dried well, and the face is oiled, as in casting from type. The plate is next laid on the moulding table, tin side pieces being unnecessary. The mould is taken in the ordinary way, and when dry enough, it is turned on its back, and the plate is gently raised from it. Thus the mould is left till ready for trimming and the other usual processes that follow.
Plates taken in plaster suffer a much greater degree of contraction than those taken by the paper process, in consequence of the shrinkage of the mould in baking and dipping, while the type is not present to offer any resistance. The amount of shrinkage in a cr. 4to page is about 1 nonpareil in length and 1 thick lead in width.
In this process, which has largely replaced the plaster method, the mould is formed in paper pulp. It possesses great advantages in economy of time and material, enabling a mould to be taken and a plate cast and finished for the press in less than J hour, and permitting a number of casts to be taken from the same mould, which may afterwards be stored for future use. The mould can also be curved to fit the semi-cylindrical casting box for making plates adapted to the cylinders of steam printing machines. In any case the process is eminently simple. Its chief drawback is that the plates never have such clean-cut outlines to the letters.
The first operation in the paper process is the compounding of the "flong," a corruption of the French word flan, a sort of pastry to which the flong is supposed to bear some resemblance. The first requisite for making flong is some good paste, which may be either made on the premises or bought ready made. It must be moderately thin and of even consistence, i. e. quite free from lumps. Several recipes for making paste will be found in 'Workshop Receipts,' Second Series, pp. 98-100. There is nothing special about the paste for making flong except that it must be good.
Suitable paste being provided, it has to be applied to successive sheets of thick unsized paper, such as blotting or tissue, in the following manner.
Begin by covering a sheet of blotting-paper with a thin, even layer of paste, and place upon it a sheet of tissue, rubbing it with the palm of the hand to reader it smooth; care must be taken that all lumps have been previously removed from the paste. Next lay a sheet of blotting on the tissue, and roll flat. To this must be added 2 more pieces of tissue-paper, the whole forming a substantial flong. When a number of moulds are to be taken, it is advisable to make sufficient flong for the whole. When completed, and not required for immediate use, place the flong separately between damp blankets, with a board and weight on the top. This will keep them moist, and in a proper state for use for some considerable time. By this plan, the workman can finish one operation at a time, and confine his attention to each successive process. If the flong becomes dry, it must be discarded, for in this case it loses its virtue, and great difficulty will be experienced in obtaining a proper depth in the mould.
The forme having been properly planed level and carefully examined, slightly slacken the quoins. With the brush provided for the purpose, rub the surface of the type with olive-oil to prevent the matrix from adhering too firmly to the type. Cut the flong to the size of the page or pages, including the side and bottom clumps. Press it between blotting-paper to remove the superfluous water, and with a long soft brush dust some French chalk over the surface.
Now place the flong on the face of the type, the tissue downwards. Cover it with a damp linen cloth, and with the hard brush commence to beat, beginning at one end of the forme and advancing to the other, in order to exclude the air from the surface of the type. If this be not attended to, it is probable that an imperfect mould will be the result. If the work be very open, or composed of rule-work, the blank parts may be pricked with a pin to liberate the confined air.