Beating the flong is undoubtedly the most difficult process to be mastered, and it is only with great care and judgment that a really good mould can be obtained. The handle of the brush must be held in such a manner as to enable the bristles to fall positively flat on the back of the flong: if it falls unevenly, the mould will be distorted, and perfectly useless, besides which, the face of the type will be injured. The process requires much practice to perform it successfully.
In time, the bristles of the brush become somewhat rounded, especially with careless beating, in which case difficulty will be experienced in obtaining a sharp and perfect matrix; besides this, the flong will require more beating, and the type will be rapidly worn down. As soon as the brush shows signs of wear, rub it carefully, while in a perfectly horizontal position, on the hottest part of the oven floor, so that any protruding hairs may be charred till they assume the level of the majority. This is sometimes done even with new brushes.
When the impression of the types is plainly seen at the back of the flong, paste a piece of thick wrapper paper on the top, and beat again; after this, lay on another piece, and proceed as before. The mould may now be of sufficient thickness, and the operator can determine if such be the case by lifting one corner and examining the impression. If any portion appears to be deficient in sharpness or depth, paste another piece on and carefully beat again in the shallow part. The whole of the flong should never be lifted off the type until it is determined that the mould is satisfactory, as great difficulty may be experienced in replacing it. If there are any "whites" in the mould, cut a piece of an old mould half the size of the open space, and paste on. This will prevent the metal from being too high in the plates, and obviate chipping. When the mould is of sufficient and uniform depth all over, softly plane the back. After having tightened the quoins, proceed to the drying process.
The melting pot and furnace have already been described. The flue of the furnace is conducted through the drying plate, on which the moulds are baked and dried. This is a long, thick iron slab, made hollow, to admit of the smoke passing from the furnace to the chimney. At one point is fixed a press for drying the moulds, the platen of which is adjusted by a strong, upright screw, having a wheel at the top. The use of dry heat for baking the mould is sometimes liable to destroy the type by rounding the bottom. A steam-chest is preferable, the entry and escape of the steam being regulated by screw-valves placed under the table.
The iron imposing surface for laying up, re-imposing the page, and making the mould has already been mentioned. A second surface should be provided, at a slightly lower level. Type-high clumps and chases are placed round the pages previous to moulding.
Proceed to lift the forme and place it on the drying surface under the press, taking care that the mould does not become misplaced during the operation. Cover the back with 2 or 3 pieces of blanket, and tightly screw down the platen, if the page be solid, but use less pressure in the case of an open or title-page. Some 10-15 minutes are required for the drying operation, after which it is well to loosen the platen, so as to relieve the forme of pressure for a minute or two, to allow steam to escape. Owing to the great heat, the quoins may possibly have become loose; it is advisable to tighten them before removing the forme to the imposing surface. The mould will now adhere somewhat tightly to the type; its removal must be patiently effected, or it will surely be spoilt. Carefully raise one corner at a time with the forefinger and thumb, lifting it higher each time, when the mould will leave the type. Should it, from any cause, such as imperfect oiling, adhere so firmly as to resist the ordinary means of lifting, the beating brush may be applied to the back.
If this fails, the mould will have to be destroyed by pouring cold water on the back after the forme has been again heated.
According to Byles' method, in use at the Bradford Observer office, the mould, instead of being dried upon the forme from which it is taken, is lifted off in a moist state, placed in a special frame, and subjected to the necessary amount of heat. The inventors claim for this process several advantages, the most important of which is, perhaps, the prevention of injury to the type; type suffers considerably from being repeatedly subjected, under pressure, to great heat, the bottom becoming rounded. A saving is also effected in the original cost of the plant, no drying process or surface being required. Fuel is saved only when the drying surface is heated independently. On the other hand, a new item of cost arises in the purchase of the drying frame. A saving of time, however, is undoubtedly effected by the adoption of this process, as the mould can be properly baked in 3-4 minutes, whereas nearly double this time is usually occupied in the operation. As the forme is not heated, the type is ready for distribution immediately the mould is lifted, certainly an additional advantage.
Before commencing to bake the mould, trim it with a pair of shears to the proper size, allowing sufficient margin to admit of the gauges lying securely on the surface. Cut a piece of brown paper the same width as the mould, and 6-8 in. long, and paste on the top edge of the page. This is to lap over the mouth of the casting box, and prevent the molten metal from running to the back of the mould when the plate is being cast. Lay the matrix on its back on the heating surface to bake. To keep it perfectly flat, and prevent its warping, place weights on the sides: type-high clumps are admirably suited for this purpose. After about 15-20 minutes, it will be perfectly dry and hard, and ready for use. Previous to placing it in the casting box, put a little French chalk over the surface with a longhaired soft brush.