What are bricks made of?

Most common bricks made today are made from a mixture clay and ground shale. 

 
The process of brick making can be traced as far back as ancient Mesopotamia and ancient Rome.  There bricks were used in much the same way we use bricks today, mainly as building materials. Nowadays the mix of clay and shale is moistened and either left to dry in the sun or more popularly baked in large room sized ovens called kilns. Today most bricks are made in factories that form the clay and shale mix into long columns.  Then once the clay has dried, the columns are cut into bricks of all sizes. 

In the early days of brick making, bricks were often made in wooden forms and pressed by hand.  It was also common for straw to be added to the clay and shale mix.  This added much needed strength to the bricks being used in building construction. 

Most bricks you will see are red in color.  This is because of the natural occurring iron that is present in most clay.  The more iron the clay contains the darker red the bricks will become when dried. Brick colors can vary from light or dark red to different shades of grays and brown.  This often determined by the temperature at which the bricks are burned.  Where at different temperatures varying colors ranging anywhere from dark red to purple can be accomplished.  The highest temperature that brick firing is safe occurs at 1,300 degrees Celsius.  This is the equivalent of 2,372 degrees Fahrenheit.   Firing in a kiln at these elevated temperatures will create bricks with a brown or grey hue.