RAKU, CHOJIRO'S METHOD OF MAKING TEA BOWLS
These plain red or black handleless stumpy mugs were not thrown on the potter's wheel but hand-carved out of local clay with wood and metal tools.
They were straight-sided but had a rim on the base on which they rested. The top was not cut level but gently undulated, very rustic to the modern eye used to everything being precise and machine-made.
The bowls would be dipped in a bucket of clear glaze made, probably, with China clay, lead and flint (silica).
The potter had to make his own kiln from bricks or brick panels which he would have to fire in a friend's or neighbour's kiln. A hatch, removable panel or lid was needed as the potter had to have access to the bowls inside the kiln. The Raku ware would be loaded into the kiln and the fire lit. It would take several hours and much stoking of the fire box with logs to achieve a temperature of 800oC (1472oF). A Raku firing temperature of 1050oC (1922oF) required much more wood and an efficient fire under or beside the kiln.
Chojiro, lacking a modern pyrometer, would have to judge when the glaze had melted satisfactorily. Nothing could substitute for years of experience. The crucial decision was when to remove the bowls, too soon or too late were equally undesirable. Once he'd made up his mind that his ware was 'done', he'd remove the hatch, panel or lid and, with long tongs and as much protection as he could muster, he'd take the red hot bowls out into the air.
The sudden drop in temperature would cause all sorts of interesting things to happen to the thermally shocked glaze. Some of these could be anticipated, some could not, which is why Raku is known as unpredictable. He'd place the bowls on fired clay tiles on the ground and let them cool off in the open air.
