TEMPERING AND PREPARING CLAY.
In early days, for tempering clay men first spaded and then stamped it with their feet ; next oxen trod, afterward the gum, later horses and wheel, finally the steam wheel took the place of horses for tempering the clay. Then in turn the steam wheel had to go, and in its stead we had rollers to break the lumpy clay, and now disintegrators and grinders to thoroughly pulverize it are employed.
The clay-crushers that are now being used commonly have smooth rollers, although almost every one of them has some device for tearing the clay to pieces. The inventors of brick making machines have learned that something must be done in the way of preparing the clay other than by smooth rolling. The day is not far distant when it will be a necessity to put more expensive, stronger and better machinery into preparing clay than has yet been done : some device which will thor oughly pull the clay apart and open the pores.
In order to make a good brick, either soft-mud, dry-pressed, semi-dry, stiff-mud, hand-made, or any other kind of brick, the clay should be properly prepared. It should be ground very fine, whether it be ground first, dried, and then tempered with water, or whether it be ground with the water ; the finer the clay is ground the better the brick will be. In the majority of cases where dry-clay brick have been found to be a failure, one of the reasons for the lack of success in their manufacture will be found to be because the clay was not properly ground.
If a good hand-made brick is desired, prepare the clay, make it smooth, work the clay thoroughly, and let the proprietor see for himself that it is prepared. In clays not ground properly, dry lumps of clay in the brick cause it to break and burst. This is proof that the clay must be properly prepared.
It is better to take the clay out in the fall, and let it be ex posed to rain and frost during the winter. By so doing it is possible to burn brick 15 or 20 cents per thousand cheaper than if the clay is taken fresh from the bank ; that is, by the old way of burning.
A machine which is going out of date, because it has been superseded by the modern pug-mill, is the old-fashioned tem pering wheel.
There has probably never been a tempering device by which clay could be prepared so evenly, uniformly, and thoroughly, and as perfectly in every respect, as with the tempering wheel ; but it costs so much more to temper clay with the wheel than by the pug-mill that the tempering wheel must soon disappear because it costs too much to prepare the clay with it.
Where there are different strata of clay to be worked, soak pits should be used in which to thoroughly mix the clays.
If there are made as many as 35,000 brick per day in a yard, the soak pits should be about 35 feet long, 12 feet wide, and 4 feet deep : put an elevator right in the centre of the pit, run a chain belt from the lower end of the pit, bringing it up on an incline, which will allow-the clay to be drawn up into the ma chine. If the clay is of a greasy character, have a little water running which will aid to slide up the incline. There should be no trouble in carrying up clays in that way when the clay is soaked before it is put into the machine.
In making tiles or fine brick, soaking the clay a few days before using it pays, and it is necessary, in order to have brick with lasting qualities, that the material should be made thor oughly homogeneous before it is moulded.
When the clay to be employed is of the bluish variety, lumpy, rough and difficult to soak, it will pay to use a crusher, as otherwise the bricks, although strong, will be rough in ap pearance and often not marketable.
In clays where rock or pebbles are present or where the clay has not been thoroughly disintegrated by frost and exposure, we do not know of any better remedy than the use of the disin tegrator, and our experience is decidedly in its favor.
The plan is sometimes adopted to temper clay by conveying it to a horizontal clay mill, into which it is fed as evenly as pos sible with a spray of water thrown on it, regulated to any de sired quantity by a stop-cock under control of the feeder.