CAUFOMNI'.
In all the large tile-works, all the operations of manufacture are conducted under shelter, and a great variety of articles are produced, of which the following list is but a part: Chimney-pots, circulars for setting furnaces, etc., column brick for forming columns, drain-pipes, drain-tiles, fire-brick, garden-pots, hip-tiles, oven-tiles, paving-tiles, pantiles, plain tiles, ridge-tiles, and anything in the line required to order.
With the exception of fire-brick, the clay used for all these articles is the same ; but for circular-brick, column-brick, kiln brick, oven-tiles, paving-tiles, and paving-brick a certain quan tity of loam is mixed with it, which for oven-tiles must be of a very good character.
To faithfully describe the manufacture of these various articles would increase the size of this chapter out of all proportion to its design. The principle of procedure is the same in eachcase, but no two articles are made or finished in a similar way, each requiring different tools and moulds.
The London tileries, which are the largest in the world, pay particular attention to proper preparation of the clay for the particular purpose for which it is to be used ; there not being the same haste to get the clay into the kiln that is shown in some smaller manufactories.
The first stage in London tileries is the weathering, which is about the same as has been described for plain tiles, the object being to open the pores of the clay, separate the particles, and thereby compel it to absorb the water more readily in the pro cess of mellowing.
This is accomplished by throwing the clay into pits, covering with water and leaving it to soften or ripen. The clay is now usually passed through the rollers and the stones taken out before it is put into soak, which is a term also used for the mellowing process.
The kilns used for burning the wares produced are usually conical in shape for more than one-half the height, about 40 feet wide at the base, and having a total height of about 25 feet from the bottom of the ash-pit to the top of the dome, which is slightly convex. These kilns are quite expensive to build,
eight thousand dollars being about a fair average ; fire-brick being generously employed in the interior. This class of kilns is largely used for burning pantiles.
Before the pantiles are placed in the kiln, one course of burned brick is laid, herring-bone fashion, one and one-half inch apart over the bottom.
The tiles are then stacked upon this as closely as they can be, one course above the other. The hatchways are bricked up as the body of the kiln is filled. When the top layer is done, it is covered or platted with one course of unburned tiles laid flat ; then on the top of these a course of burned pantiles is loosely laid. The hatchways are carefully daubed over, the fires lighted and kept gently burning for twenty-four hours, and then grad ually increased, until at the end of six days they are left to die out, the burning being accomplished.
The class of goods which the kiln contains has a great influ ence upon the quantity of fuel consumed in a burning, chim ney-pots, garden-pots, etc., not requiring so much as more solid goods.
In this country, the manufacture of roofing-tiles is a compar atively new industry ; but it is rapidly growing in public favor, and their employment is becoming quite general.
Many large and costly, as well as small or ordinary dwelling houses, church buildings, extensive work-shops, barns, etc., are covered with tile roofs.
With us, the tiles are usually of three colors, red, buff, and black. The color of the red tile is produced by the employ ment of clay containing a large per cent. of oxide of iron ; this is sometimes present in the beds with fire-clays, which are the class usually employed for roofing-tiles ; at other times, it is necessary to mix some foreign clay, containing a large per cent. of oxide of iron, with the material.
The color is made deeper and more uniform by rubbing the tiles with finely-sifted red moulding sand ; this should be done while the tile is quite damp, so as to get the sand to stick or hold to the faces.