Of course the front will be hotter than the back, but if saggars can be obtained, the glaze may be placed in them to the front with the biscuit protected behind. Clay shapes fired up at the front may bend towards the fire, and any broken crocks should be used to screen them.
The making of rough saggars is not difficult if a supply of fire clay is to hand, or clay and grog will serve at a pinch. The clay is rolled out and the saggar stuck up, much as described on page [32].
Every joint must be carefully welded and the whole thoroughly dried. Then they are fired up in the kiln, very gently at first, and carried up to a temperature considerably above that which they will be subjected to when in use.
For small trial crucibles ordinary clay mixed with pitchers and powdered coke proves satisfactory; the coke when fired out renders the body porous and the heat penetrates more swiftly.
Fig. 71a
To construct the muffle kiln shown at Fig. 72 the aid of a competent bricklayer would probably be required. In this kiln glaze and biscuit would fire up without saggars, but will take rather longer. The plan and elevation of this particular kiln are given with all reserve. The design would probably
require considerable adjustment and modification before complete satisfaction was obtained.
Fig. 72