The kiln, which was designed by Michael O’Brien and completed
in 1992, is a 400 cubic feet round down-draught type,
with six `Bourry’ fireboxes fed by pre-heated combustion
air from ducts running alongside the exit flues.
A
normal firing to cone 04 : 1060 degrees centigrade, takes
about thirty six hours and consumes between two, and two
and a half cords of round coppice hard wood, and pine slab
wood.
A
typical pack consists of a mixed load of large and
small plant pots and raw-glazed slipware,
varying in size from small domestic pieces to large
glazed jars . To bring the largest pots through the
firing successfully, a pre-heat of twelve hours
to 200 degrees centigrade is necessary; this drives
off residual moisture in the pots
without splitting them.
Towards
the end of the firing, holding the temperature, or 'soaking',
the kiln at 950 degrees centigrade for an hour or more,
helps to create an even temperature from the top to the
bottom of the kiln chamber, and to encourage the cones (heat
work indicators) to bend together when bringing the kiln
up to top temperature: 1060 degrees. Soaking for extended
periods at top temperature can use large amounts of extra
fuel, and run the risk of over firing the pots in the top
of the kiln.