Clamp or open kiln is a temporary structure where dried bricks are stacked in alternate layers of fuel, i.e., both bricks and fuels are placed in alternate layers. Locally available materials such as grass, rice, husk, wooden chippings, cheap quality woods and dried cow dung are used as fuel. About 20,000 to 1,00,000 bricks are available after burning and cooling. It takes around 3–6 months to complete the burning and cooling of the bricks (Fig. 3.4) in the clamp.
Figure 3.4 Typical arrangement of fuel and bricks in clamp or open kilns
The main advantages of this method are that its initial cost is low, fuel cost is low and there is no need of a permanent structure and skilled labourers. The regulation and circulation of heat are not possible, and hence only 60% of good-quality bricks can be expected. Further, only a small quantity of bricks can be manufactured at a time.
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