What Are Bricks Made Of? How Are Bricks Made?
Brick is one of the strongest and most durable building materials available, and humans have been using them for more than 5,000 years. Many people want to know what makes bricks so durable and what ingredients go into their creation. Keep reading as we look at how our ancient ancestors made them and if we still do it the same way.
What Are Bricks Made of?
It might surprise you to learn that you use only a few ingredients to create a brick. The first bricks used only dirt and straw, but builders learned that clay heated in a kiln would create a stronger material. Builders continued to make bricks by hand until the 20th century, and the colonies in the eventual United States started building them to sell commercially in 1611. Today, bricks are heated clay and shale mixed with water. These natural materials don’t create any emissions and help make for a cleaner environment.
How Are Bricks Made?
Gather the Materials
Bulldozers and other large machinery dig up different types of clay and shale and transport them to a facility that crushes them up into particles about 4 inches wide.
Crush and Mix
The different types of clay are mixed depending on what kind of brick is to be created and sent back for more crushing. They will continue to be crushed until the particles are small and even.
This crushed clay and shale powder will be formed into bricks in one of two ways.
Semi-dry Pressed Brick
Semi-dry bricks have 10–12% water content mixed with the powder. The powder is placed into molds and pressed to form a smooth brick with sharp edges and a shallow depression on the top surface. The sharp edge is called an arise, and the depression is called a frog.
Extruded bricks are more common than semi-dry pressed bricks, and they are made from a powder that contains more water. These bricks start with clay mixed with up to 25% water, and this clay is pushed through a tube, similar to that of a pasta machine, with a brick-shaped tip. When enough clay emerges from the tip to form a brick, a wire cuts through the clay to sever it and start the next one. These bricks start smooth, but the manufacturer can add a pattern or texture before baking them.
Dry the Bricks
Extruded bricks can take too much time to dry naturally, so manufacturers often add perforations to speed up the process. These perforations also reduce brick distortions and baking and cooling times. These bricks then pass through a drying fire or sit in drying racks depending on their moisture content.
Since pressed bricks have much less water, manufacturers stack them and dry them with a small fire.
When the bricks are dry, the manufacturer will bake them using one of three methods to bake the dry “green” bricks at up to 1,800 degrees Fahrenheit to turn them into their finished product.
The down-draught kiln is a rectangular area with a perforated floor and a curved ceiling. The bricks are stacked on the floor with fires on the sides, which cause hot gases to circulate and bake the bricks. When they are finished, the fires are extinguished and the bricks removed.
The Hoffman Kiln uses a slightly different system that enables manufacturers to fire the bricks continuously, so they can remove finished bricks and replace them with new ones.
- See Also: How to Paint Brick in 4 Easy Steps
The tunnel kiln is a continuous firing method. The bricks are pushed past stationary fires in a system that is not that different from the conveyor-belt pizza oven found in many pizza shops. Manufacturers use the heat to fire the bricks and the exhaust to dry them, making it more efficient than other methods.
You can make bricks from nothing more than clay and shale mixed with water. Once you form the brick and dry it, you must bake it at an extremely high temperature to create the finished product. The high temperature means that bricks take a great deal of energy to create, but they have a long lifespan that can last 100 years or more, even in bad weather.
Featured Image Credit: mariastone, Pixabay