Hoffman kilns with multiple fires
Hoffman kilns with multiple fires
The Hoffmann kiln caught on fast – in 1870, a decade after the first one was built, there were already
639 units operating worldwide. It remained the most important technology to bake bricks, tiles and ceramic
pipes for a century.
The original design was adapted to many other forms, some of them rather spectacular. An important
improvement to the Hoffmann kiln was made by Jacob Bührer from Switzerland. He generated great fuel
efficiency and a large increase in output by the use of a continuous kiln with a tunnel about twice as
long and half as wide as those commonly in use. In order to overcome the difficulties of construction
and loss of heat inherent to an extremely long and narrow kiln, Bürher arranged his tunnel in a zigzag
manner. Whilst externally his kiln is square in plan, its effective tunnel length is almost double that
of a Hoffmann kiln.
Where very large outputs were required, “shank kilns” were built of a shape similar to one of the plans
shown above. Owing to their special shape several fires could be kept going in each kiln with a minimum
of labour, and the cost of erection was less than that of several continuous kilns of equal total capacity.
At the beginning of the 20th century, already over 200 of these shank kilns were in existence on the continent
with an annual output varying from 5 million to 50 million bricks each.
A continuous kiln was sometimes enlarged by adopting the “Shank” principle just described: such an
alteration to an old circular Hoffmann is shown on the left. In enlarging a kiln this way it was mostly
necessary to supplement the chimney-draught by the aid of a fan. Some large continuous kilns were also
equipped with several chimneys.