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close this book Village-Level Brickmaking
close this folder Firing A Field Kiln With Firewood
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View the document Organization Of The Kiln Site
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View the document The Firing Process
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View the document Problems With Fired Bricks
View the document Firing A Field Kiln: An Example
View the document Time Estimate For Building And Firing A Field Kiln
View the document Firing Principles - (Points To Remember)
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The Firing Process

When clay bricks are heated to a high temperature, a chemical reaction occurs in the clay which makes the brick permanently hard, durable and resistant to weather and water.

When a brick is heated to a temperature between 20C and 150C, it loses most of the water added to the clay during the preparation phase.

When heated from 150C to 600C, the clay brick loses its remaining water. When firing a kiln, you will see a white vapour or steam coming from the top of the kiln during these first two phases. If you were to stop the firing process at 600C, the bricks in the kiln would be useless for building purposes since they would not be stabilized and would easily be worn down by wind and rain.

When the temperature starts to rise over 600C, chemical changes begin to occur in the clay which give the brick colour, hardness and durability. Temperatures of 900C and above cause vitrification to occur. This means that a small quantity of glass-like material forms which helps glue all of elements in the clay together. It is after this point of vitrification that the brick will be at its hardest and most resistant and will be ideal for construction.

The final quality of the brick will depend on the amount of vitrification which occurs. It therefore is essential that the temperature of the kiln rises to well above 900C in order to obtain a well-fired brick.


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