The sheet-copper bands which conduct the electricity from the battery to the trough should be about 1/32 in. thick and 1 in. wide; wire has not sufficient body to carry the necessary amount of current. Their width is regulated by the extent ' of plate surface in the battery, but it is important that the bands shall be large enough, or the deposit is apt to be retarded; better have them too large than too small.
The surface of the depositing trough must be perfectly free, hence the conductors should be so secured as not to interfere with placing the moulds. A 9-in. board may be first fixed to the wall at the back of the trough and battery, and the copper bands screwed flat to it until they reach the point where the connections are made. When electrotyping is done on a large scale it is advisable to have more than one connection from the battery, so that the current may be of uniform strength throughout the solution. After the first connection is made, the conductors are carried along to the centre of the trough, where the second junction can be effected. If the depositing vat is large, and this plan is not adopted, the deposit is liable to be thicker and mora rapid at the end than in the centre of the solution.
For supporting the moulds and copper plates in the depositing trough, rods 1/2 in. in diameter are used, slightly shorter than the width of the trough, so as not to hang over, or they will interfere with the workman; they are commonly made of brass, but copper is more durable, as the zinc in the brass quickly becomes affected, and after the rods have been a little time in use, corrosion sets in.
Copper binding-screws are employed for securing the zinc plates and connecting the wires. The moulds are hung from the rods in hooks of copper wire about 1/4 in. thick, well turned up at the ends, to admit of the moulds being moved without slipping off. A thick deposit of copper will form on the ends of the hooks if they are allowed to touch the solution, and must be removed with emery paper or a file; the copper rods may be cleaned in the same way.
Be sure always to have a good supply of water in the battery room; also a lead-lined trough beneath the tap. At one end of the trough, fix an inclined board, covered with sheet lead, on which to clean the moulds before putting them into the trough. A useful accessory is 12-18 in. of rubber pipe, with a fine rose at the end. Nail a fillet along the outer edge of this board to keep the water from running on the floor.
The metal pot is rectangular in form and usually rather large, to admit of the backing-pans being lodged on the surface of the metal with little difficulty. Fumes from the molten metal may be carried off by suspending a large sheet-iron funnel immediately over the pot, and providing it with an outlet into a flue or chimney. The pans may be either lifted by hand on to the metal, or swung from a suspended framework, on which a small carriage can travel, about 4 ft. above the pot.
The iron backing-pans are of a size to accommodate 2 demy-4to shells, with a handle at each end for the hooks on the travelling carriage to hold by. But the backing of shells, in almost all instances, is done by placing the backing-pan, containing the newly-tinned shell, on the iron surface, and pouring metal from the ladle.
Besides the melting pot for wax for "building" purposes, another must be provided on a separate bench for " stopping-out " the back and those portions of the moulds where no deposit is required. An iron or leaden slab should be placed near, on which the moulding pan can rest, and on which the superfluous wax may run; the latter can then be easily scraped from the surface and replaced in the pot. A wooden balk is liable to become quickly indented by the moulds, and the wax, filling the holes thus made, renders the task of cleaning more difficult. A brush, similar to that used for black leading grates, is employed for "stopping-out." Waste wax and dross from the melting pots, which may contain a small percentage of copper, should be collected and sold.
Work for electrotyping is generally scut to foundry imposed in small chases; 2 or more 8vo pages may be placed together, with type - high furniture between. If screw chases and type-high furniture, already described, have not been used, the forme must be " dropped " upon the imposing surface, and reimposed, first carefully examining on the inside, that no dirt be adhering.
When the forme is screwed-up, the face of the type is well brushed over with lye, to remove dirt from the beards of the letters, then dried and planed thoroughly, taking care that all the spaces are pushed down. Next the type is brushed over with graphite, until the surface is perfectly bright; this assists in the separation of the wax when lifting, after the impression is taken, and to some extent it ensures the graphite finding its way into all portions of the mould.
If there are wood-blocks in the type, the page should be examined to ascertain whether they are of the same height as the type. If not, they must be underlaid with glazeboard. Turpentine should be used for cleaning woodblocks prior to moulding, as it causes no warping. After blackleading, be sure that no dust remains on the surface.
Meantime the moulding-pan will have been filled with a composition made by mixing 20 lb. beeswax with 3 lb. Venice turpentine and 1/2 lb. graphite, keeping it perfectly free from dirt. Several frames at once are laid upon the iron imposing-surface and filled to the level of the sides of the frame; if it sinks on cooling, more is added till the frame is full. Any that flows over the sides speedily solidifies, and may be put back into the melting pot. Air-bubbles must be carefully and quickly removed. As the wax rapidly becomes solid, the pouring should be performed as speedily as possible; if allowed to become thick, the surface will not be level. Should the wax seem inclined to crack in cooling, owing to a low air temperature, a little more Venice or virgin turpentine may be added.