22 October 2015

OPENING THE KILN

However long you do ceramics, a kiln firing remains nerve-wracking and you always open the kiln with trepidation. Today I finished a firing and took out 70 pieces, nearly all of them good.

Firing an electric kiln isn't as easy as is often made out. Sure, you can get the controller to switch the kiln off while you're asleep in bed, but kiln thermometers are inaccurate, all kilns have hot and cool spots, and anyway you have to measure heat-work, not temperature, and that requires pyrometric cones. In my 14 cu.ft. (400 litre) kiln I use two sets of cones because the top and bottom can differ by almost a cone (roughly 20 deg. C).  The last two hours of firing call for as much fiddling with sector switches, vents and bungs as a gas kiln.

Through repetition and experiment I've eliminated the grossest faults in my firings. Crazing and crawling are the opposites of each other, but I've had them both. Glaze chipping off the edges of pots is a hazard of tin glaze, and I've pretty well got rid of that. Colours running - got rid of that too. There's always room for improvement, of course - a slight adjustment of glaze thickness, some modification of the colour, better control of the brush, and in this firing I tried some new designs which will go into production when they've been refined. But on the whole, satisfactory.