in a raku kiln. When
I designed and built the prototype for the wood-fired stoneware kiln,
Fred Olsen's fastfire kilns were all the rage and my design had much in
common with Olsen's although its origins were in the little wood fired
raku kilns which we built in the 1970s. These little kilns
had two fireboxes and the chimney sat on top of the fireboxes
behind the tiny firing chamber. I don't know where the design
originally come from but we built more than a dozen of these little
kilns out of housebricks salvaged from demolition sites. They
were a joy to fire and some of the pots that emerged from them were
unbelievable gems! We could scrape 1050 degrees centigrade
used lead and borax glazes flavoured with copper, iron and (sometimes!)
uranium! Heavy reduction was achieved by blocking the chimney
with a pice of broken kiln batt and adding a bit of used sump oil to
the fireboxes. Magic!
kiln at Blackhills was built to the same design which we had used for
an earthenware kiln at Pantasaph in North Wales five years earlier.
Three large fireboxes run underneath the kiln, each about six
foot long. The 64 cubic foot chamber and the chimney are
top of the fireboxes.
I started off firing the kiln to 1300 degrees centigrade in about ten
hours, I now take thirty hours to reach 1250 - and would fire longer if
exhaustion didn't intervene. I also cool as slowly as
clamming up every crack with clay. The cooling takes a couple
days and it is this long cooling cycle that give the glazes
soft maturity and bring out the rich reds in the iron bearing clay.
The importance of the cooling cycle has not been given enough
attention. The vogue for fastfire and speed cooling produced
bright, colourful, shiny glazes but with none of the depth and
mellowness of the same glazes cooled slowly.
fire to a thousand (centigrade) in oxidation over about
twenty hours, care being taken to minimise smoke and flame
entering the ware chamber. At a thousand, we reduce hard for
hour or more without any temperature rise. Then the
in the kiln is allowed to rise slowly (a mixture of reduction and
oxidation) until the temperature reaches 1200. The kiln is
soaked for a couple of hours and reaches about 1250, by which time cone
11 is down at the top and bottom. I try (not always
to leave cone 12 standing.