Knowing how bricks and tiles are made

The industry of bricks and tiles

The story of bricks goes back to the beginning of civilization. When men began to build temples and palaces, they needed a cheal and lasting building material. They learned that this could made by shaping clay into blocks and allowing them to harden, either in the sun or in artificial heat. Kiln-burned bricks made by the Babylonians 6,000 years ago still exist. The entire site of the vanished city of Babylon is now little more than a huge mound of dirt. It came from the reaking fown of the huts and houses of sun-baked brick.

The ancient Egyptians had an unending suppy of brickmaking material in the clay which forms the bed of the Nile River. Brickmaking was always one of their chief industries. Because this clay did not hold together by itself the Egyptians used to add chopped straw or reeds, which served to bind the bricks together. During the years of their bondage in Egypt the ancient Hebrews were set to making bricks. The cruel taskmasters added to their woes by requiring them to make "bricks without straw.

They were ordered to furnish their own straw without lowerng the number of birkcs produced in a given day. The Egyptian bricks were nearly all sun-dried, not kiln-burned. They were like the adobe bricks used in Mexico and the southwestern paft of te United States. Adobe bricks can be used in places where there is no frost to freeze the moisture in them and crack them

An Important Modern Industry

Today, brickmaking is one of the world's great industries. Nearly every large community has its own brick plan, unless it has a good supply of other building materials close at hand. The industry is widely scattered because bricks can be made of almost any kind of clay, mixed with sand.

Brick clay is largely hydrated silicates of aluminum, with oxide or carbonate of iron and various other substances. When they are burned, bricks of this composition have a buff, salmon or red color, due to the presence of the iron. If much carbonate of lime or chalk is present, the color is sulfur yellow. If sand is not already present in the clay, it must be added. When there is too much sand the bricks are likely to crumble. When there is too little the bricks will crack easily.

Preparing the Clay

Clay for bricks is dug by power shovels, crushed by hammerLearni devices or rollers, and sifted to remove rocks or other bulky material. Then the screened clay, sometimes with anthracite (coal) dust added to help the burning, is mixed with water and kneaded thoroughly by great revolving knives in a pugmill. Modern practice uses of the three machine systems - the soft-mud, the stiff-mud, or the dry-clay machine. The stiff-mud process is most commonly used in the United States. As the clay is forced out in columns it is cut by wires. 18 bricks at a time. Some machines turn out 300,000 bricks a day.

Workmen pile the bricks on cars, about 1,000 on each. The cars carry them through tunnel driers that remove nearly a pound of moisture from each brick in 24 hours. The tunnels are heated by exhaust from kilns, and ventilation keeps the air dry. If the air gets to damp, moisture from the brick's interior comes to the surface. The moisture carries with it the soluble salts of the clay, which cause the white scum seen on poorly dried bricks.

In the soft-mud process, machinery presses the mixed clay in molds. The brick is not as hard or durable as the stiff-mud brick. For the expensive dry-pressed brick, clay almost dry is pressed in steel molds. This type is used for artistic front-wall finishes or decorative interior work. Sometimes brick is dried in the open air or on steam-heated floors.