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Feeding of Hoffman kiln

Feeding of Hoffman kiln
Some Hoffmann kilns were fuelled by gas, but mostly the fuel was coal. The ceiling of a ring oven
contained many rows of openings – covered with air-tight metal caps – which were known as “feed holes”
(see drawing and picture below). Experienced “stokers” dropped a small and precisely dosed amount of
crushed coal through the holes above the chamber that was fired, using a small coal shovel.

They formed a team with the “setters”, who built the stacks of unfired green bricks inside the chambers.
These stacks were positioned so that they contained flues and channels to ensure even baking. Right
underneath each feed hole the bricks were arranged to form “fireplaces”, in which the fuel could be burnt.
These were hollow shafts built of bricks, with occasional projecting bricks to prevent all the fuel from
falling directly to the bottom.
Once the stacks were built, the chamber was closed by a door or a temporary brick wall, not to be opened
again before unloading the bricks several weeks later. It was not necessary to enter the chambers to light
the fire: once a room was preheated enough by the hot gases of the chambers next to it, the temperature
inside was high enough to spontaneously combust the coal that was dropped through the feed holes.