When the brick is fired at a sufficiently high temperature for a controlled length of time, chemical changes occur and these result in a harder and more lasting product.

1. The softness necessary for moulding is lost.

2. The clay shrinks.

3. Mechanical strength is greatly increased.

4. The material becomes durable and resistant to weathering

5. Changes in colour occur.

The properties of these bricks and nature of these changes depend upon the composition of the clay, the method of manufacture and the conditions during the firing. The firing of bricks takes considerable skill on the part of the person in charge as the bricks have to be set properly in the kiln, which will allow for a good firing, knowledge of temperatures and how to achieve the desired colours and textures.

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