It now remains to make a case of the bottom mold. The bottom piece of the block mold is taken and sized and with a strip of paper bound around it, plaster is poured. The two are detached when set and the case is finished. It consists of seven pieces; three are used in each half and one for the bottom.
Thus equipped it is possible to make any number of working molds and if the case should wear out or be damaged, a new one can always be made from the block mold. The block mold itself, having been sized, is no longer absorbent and cannot be used for making vases. The working molds should be thoroughly dried before using and they will last longer.
Flat ware, such as plates and saucers, is made on, not in, a mold. The diameter of the plate having been decided upon, a block of plaster three inches wider is run. This is placed on the center of the wheel or jigger and in it the face of the plate is turned. This must be sunk below the level of the block and when finished, must appear as though the plate itself were embedded in the plaster. One half of the thickness of the edge is shown in such a way that there is no under cutting. Just outside of this edge the plaster is turned so as to slope gently up to the level of the block.
Fig. 11. Block of plaster with face of plate turned. B, height of plaster to be poured. C, rubber belt.
Without removing the block from the wheel the face of the plate is well sized, a band of belting is arranged, of the same diameter as the edge of the slope and plaster is poured to a depth of three inches. Out of this the back of the mold is turned as shown in the illustration (Fig. 12).
Fig. 12. A, block of plaster. B, mold poured on face of plate and turned.
The top of this as it lies upside down is shaped with a straight, almost upright slope which enables the mold to be set securely in the wheel head. Around the exposed edge of the original block, three or four natches are now bored or cut. They should be placed at irregular distances so that there will be no doubt as to the putting together of the sides of the case. If two circular pieces of plaster have to be set together and held by natches there should always be either this irregular spacing or some distinctive mark, because if this be not provided for, two or three trials will always be made before the correct fitting is found and these trials wear out the natches very quickly.
