The history of brick making
The basic foundation of all strong and sturdy construction involves bricks. The earliest bricks were used in 7500 B.C. and were made of mud. Mud bricks were used by many civilizations, such as the ancient Egyptians and the Indus Valley people. Proof of the latter can be seen in the ruins of Mohenjo-daro and Harappa. The first sun-dried bricks were discovered in 4000 B.C. in Mesopotamia. Fired bricks were used by the Roman Empire, who through the use of mobile kilns spread the practice of brick making to many parts of the world.
In China, the earliest traces of fired bricks were found in ruins of the Western Zhou dynasty. The name and birth date of the brick makers were stamped on the bricks, so that the government could identify them if the bricks made were below the standard expected.
In Europe, bricks were of great importance during the 12th century, inspiring the development of Gothic architecture. These buildings, made entirely of bricks, can be found in various parts of Europe such as Denmark, Poland and Germany. Towards the dawn of the Renaissance period, the brick construction was covered with plaster due to its rough, unfinished appearance. Before the existence of canals, railways and good roads, bricks had to be made in a location close to where they would be used. This was necessary, because the carrying of heavy bricks over long distances usually raised their price. During the Victorian era in London, due to the heavy fogs, bright red bricks were used in the buildings to avoid road accidents.
The quicker method of making bricks as well as their economical manufacturing made them a good replacement for stone. This was the reason why most of the buildings constructed during the Industrial Revolution were made of brick. However, as the trend towards skyscrapers started to grow, the use of bricks in their entire construction was not feasible. In order to support the giant buildings, more bricks would be needed in the foundation, leading to a massive loss of floor space in the lower floors. The highest building made out of bricks can be found in Germany – St. Martin's Church, completed in the 16th century. Recently, bricks have been used mainly for smaller buildings or as a decorative façade for concrete and steel constructions.
Methods of Brick making
While current bricks used in buildings are made from clay, calcium silicate, concrete or quarry stone, real bricks are ceramic. In general, bricks are made up of fixed quantities of sand, clay, lime, iron oxide and magnesia. Clay is currently the most common type of brick found and is made by using any of the three methods mentioned below:-
1. Mud Bricks - This is the cheapest method of making bricks. Here, raw clay is first mixed with sand to ensure that the overall size is retained. It is then ground and water is added to get the right consistency. After being pressed into moulds made of steel, the bricks are heated at a temperature of up to 1000 degrees Celsius. In modern practices, bricks are transported on conveyor belts or in cars through a tunnel kiln (oven) which is constantly being fired or heated. This ensures that all the bricks are the same.
2. Dry pressed Bricks - Here, a thicker clay mixture is heated for a longer time to obtain sharper bricks. They are more expensive.
3. Extruded Bricks - This method of making bricks produces stronger and denser bricks. The clay is mixed with varying levels of water and the finished result may be perforated. These holes mean that less clay is used and so reduces the cost of the bricks. They are also easier to transport.
Calcium Silicate bricks are made by mixing together lime, quartz or flint and mineral colouring elements. They are found commonly in Sweden, the U.S and Canada. In India, they are made of fly ash, lime and gypsum.
Stone bricks may also be used, but they are very heavy and a lot more time and skill is required to build with them. The elements used in stone bricks include granite, limestone, marble, quartz and sandstone.
Brick making in India
In India, bricks are mostly made by hand through the use of the Trench Kiln devised by the British engineer W. Bull. Here a trench is dug and an exhaust chimney built in the centre. Raw unfired bricks are placed one on top of the other in a manner to allow air to flow among them. This construction is covered with a roof made from finished bricks. Through the holes in the roof, the brick makers introduce fuel such as coal, oil or wood. Metal sheets or boards are placed in such a way to allow the fresh air to circulate among the newly heated bricks first. The heated air rises through the chimney and is sucked back in, thereby enabling the heated air to be used again and again reducing fuel expenses. Anywhere between 10,000 and 25,000 bricks are made in a single day through the continuous hard work of many labourers.
What gives Bricks their appearance?
The colour of bricks changes depending upon the elements that are mixed together to create them as well as the time and temperature of heating. Bricks with higher iron in their mixture appear pink in colour, while those with more of lime appear white. Concrete blocks are essentially bricks that are grey in colour. These blocks are steam cured and not heated. Many are made to resemble actual clay bricks.
Bricks are also often glazed to make them appear more finished or decorative. The glaze can be achieved by adding salt during the heating process, or by dipping the finished product into a glaze material. In the latter, the bricks are heated again to ensure that the glaze does not rub off.
Bricks must be of a size that is easy to deal with during construction. The labourer should be able to carry it with one hand while applying the cement/mortar with the other. The width of the bricks is fixed in size because of the average size of the human hand. The length of the brick is double this size allowing the alternating layers of laid brick to follow the same pattern.
Bricks can be made in different shapes and sizes for stronger outcomes. If bricks are larger, fewer are needed and the mortar used is also much less and so they are cheaper. Bricks, as mentioned earlier, can have holes or be hollow, making them lightweight and so more economical.
Bricks are used to pave roads that don't see much road traffic – mostly pedestrian walkways. They are also used to make the glass industry's furnaces. While bricks can be used to make buildings, they have been proven to be the worst hit in earthquake-prone areas. During the quakes, the mortar holding together the bricks start to crack, resulting in a collapse of the entire structure. Even if they are not used to make buildings and houses, they may be used to cover the concrete exterior, for an antique and neater appearance.