Handles.—Handles are always formed separately from the ware to which they are to be attached, and may be made in several ways. Those which have the same section throughout are cut from a long strip of clay, which has been forced through a metallic template of the re quisite shnpe, placed at the base of coni cal case, in which, works a plunger driven by a serew and fly-wheel (Fig.
1144). Ornamental decorated handles are formed by pressing the plastic clay into moulds of plaster of Paris ; and light hollow handles, by the itijection of a liquid clay mixture into a mould of plaster, end by the deposition of the clay upon the porous surface of the mould (compare Casting, p. 1596). Handle, spout, or whatever is applied to ware in this stage, is fixed by liquid slip, every trace of the joint being carefully removed. At this stage, also, any holes that may be required, as, for instance, in the strainers of tea-pots, sre pierced. In the latter case, all the holes are pierced at one blow, by a tool with an equivalent number of points.
Moulds.—Reference has already been made to plaster of Paris moulds. Few, except the smallest vessels, are made by the thrower, the great majority being formed in moulds. The moulds there fore form the most valuable and, at the same time, the most cumbrous element in the potter's plant. The material of which the moulds are made is plaster of Paris, which is preferred on account of its power, when dry, of absorbing moisture from the clay in contact with it, also on account of the ease with which it can be manipulated. Any number of moulds can be made successively from one model prepared in clay or plaster of Paris, by simply pouting the plaster, rendered liquid by admixture with water, over the model, and allowing it to set. If the surface of the model be covered with a pattern in relief, the mould will have the same pattern impressed, and the clay ware will have the same pattern in relief. In this way, tbe raised basket-ware, fluted, and flower and leaf patterns on c,ommon ware are produced.
Batting.—The process of moulding or " pressing " consists first in forming thin layers or bats of clay, and then inserting and pressing them into moulds, which are generally in two pieces, to facilitate the insertion of the " bats," and the removal of the moulded viare. Bats of clay are
formed by hammering out blocks of clay on a bed of pla,ster of Paris, with a wooden 10-lb. mallet, of the shape represented in Fig. 1145, or by machinery. The employ ment of machinery is desirable, as the process of hand-batting is both slow and laborious. In the bat ting-machine represented in Fig. 1146, the clay is pressed between two iron discs with surfaces of plaster of Paris. The upper disc rises from and falls upon the lower stationary disc by means of cranks driven by power. The thickness of the resultant " bat" can be regulated by set-screws ; the clay is fed into the small hopper shown in the figure, which opens automatically, to allow the clay to fall upon the lower disc when the upper disc is at its highest point. A modified form of this machine has been introduced, in which are three stationary discs, fixed upon a revolving table, in such a manner that they are successively carried by the table under an upper disc, to which an up-and-down motion is supplied, as in the single battiug-machine, already described.
Pressing.—The simplest form of pressing is that employed in the manufacture of plates, and is known as " flat-pressing." The mould is an exact reproduction in plaster of Paris of the inside of the plate to be produced. It is placed upon a block of plaster of Paris, held by four bent wrought iron anus attached to a vertical spindle, to which, motion is supplied either by hand connected with a large ver tical wheel turned by a handle, or by the friction of an endless band driven by power. In the latter case, a pulley is fixed to the lower end of the spindle, to which the band can be transferred from another free pulley, on which the band travels when the spindle is not in use.
This band is transferred by the pressure of the operator's knee upon a lever c,onuected with the free pulley. The spindle with the iron frame and plaster head is known as a " jigger." The old process was to place upon the plaster mould a bat of clay, to press it with the hand until its internal surface assumed the form of the mould, that is the form of the inside of the plate, and then to press upon the upper surface of the clay a template or profile having the exact form of the bottom of the plate, the pressure and profile being applied whilst the spindle was in motion.