Hoffman kilns in use today
Hoffman kilns in use today
Today, ring ovens (and some alternatives) are still used in developing countries, and by some artisanal
producers of traditional bricks in the developed world – their products being mostly
aimed at the renovation of historical buildings.
In some developing countries a low-tech version of the Hoffmann kiln is used, in which the arched roof
is replaced by a cover of bricks and sand. These are called Bull’s trench kilns – named
after its British inventor W. Bull – and they are common in Pakistan, India, Bangladesh, Nepal (some
great pictures here) and Myanmar.
These semi-continuous kilns – 100 to 150 metres long and usually built in a trench – produce bricks of
similar strength, but with a lesser esthetic quality. In a Bull’s trench kiln the light
sheet metal chimneys are moved around every 24 hours by a team of workers in order to fire a different
part of the tunnel.
These kilns are less efficient than a real Hoffmann kiln, but still more efficient than periodic kilns.
Their great advantage is that they are cheaper to built. In a real Hoffmann kiln it is
necessary to burn some six to ten million bricks before the saving in fuel has compensated the cost
of the construction of the oven.