Variations on these are achieved by regulating the firing or by the addition of metals such as manganese to the clays at the mixing stages. Applied colours can be achieved by blowing coloured sands onto the column of clay as it moves towards the moulds. Likewise texturing is done in a similar fashion. For glazed wall and floor tiles introduced colours can be held in the glazed surface which is fixed during the firing process. The glazing process is also widely used in the production of clay drainage pipes which makes them an almost impervious material.
Brick making is a truly traditional art and bricks are a valuable building material.
To reduce costs mass production techniques have developed. History proves that this problem is one of bad production techniques rather than one of the material type or of the traditional process. To justify the high energy consumption that brick production requires, the consumer must be sure that the bricks they choose are totally suitable for the job to be carried out. Cement Manufacture and Use Brief History Hydraulic cements were first used by the Romans. The composition then was of lime and volcanic ash, which slowly reacted with the lime in the presence of water to form a hard mass.