TEMPERING OF THE CLAY.
Various methods for tempering clay are in use in different parts of the country, the hand-method, the pug-mill, the ring pit, and the combined clay-rolls and pug-mill being used. The hand-method of tempering is sometimes used in country places, and the clay by this process is tempered by throwing the material into a pile, and at the same time saturating it with water. The pile of clay thus formed is termed a " soak heap," and the clay is allowed to soak for about twelve or fourteen hours, when the hand-temperer pulls down part of the "soak heap" with a hoe and thoroughly wets the portion of clay thrown down and turns it over several times with a spade, after which the clay is formed into a small cone-shaped pile. The hand-temperer then cuts through the small pile of clay with a tool termed a "slasher," and after "cutting and slashing" the clay for a short time in this way, it is again wetted and then turned over with a spade, after which it is in condition for the moulder. The usual work required of the hand-temperer is to " throw up," soak, and temper sufficient clay to make 2333 brick, and in addition he is required to wheel from the floor and hack in the drying shed about 65o of the green moulded brick.
The method of tempering clay with a pug-mill is so well known that it is scarcely necessary to enlarge upon it here ; but a full description of the pug-mills and ring-pits and meth ods used in tempering clay for hand-made brick will be found under the respective sub-heads of "Pug-Mills," and " Ring Pits " in this chapter. Before the clay is ground by the pug
mill it is placed in a semi-circular pit, and after being covered with water it is allowed to soak over night. When the pug-mill is operated by horse-power, one horse will grind sufficient clay in about six hours to make 7,000 brick.
The ring-pits employed for tempering clay have a capacity for grinding and tempering sufficient clay to make 14,000 brick. The pits are usually about two feet deep and twenty feet in diameter, and the tempering-wheel, which is about six feet in diameter, is made to revolve around the pit by means of suitable gearing, which is so arranged that as the wheel revolves it is gradually thrown from the centre to the circumference of the tempering pit, and is afterwards gradually again drawn toward the center. Ring-pits can be operated either by horse power or by steam-power, but in works producing brick in large quantities the latter method is the one commonly em ployed.
The object of tempering the clay is to thoroughly mix it, and prepare the material for the use of the moulder, who must have it in a condition not too soft nor yet too hard, but in a suitable state of plasticity to be easily and solidly moulded into brick. After the clay has been properly tempered and brought into the desired state of plasticity, the next step in the process of producing hand-made brick is that of