C. A. Sanger on mon 5 jul 99
Peter Pinnell visited Emporia State University some years ago, and
explained an easy, clean, and effective method for firing blackware.
The pots are previously burnished to a high shine, then "bisqued" to
cone 010 for greater strnegth. (Any higher and you'll lose the shine.)
If you want designs on the pots, make a thin slip of the body clay, and
use it to paint with. Those painted areas will be matt black after
firing, the burnished areas a shiny black. The "kiln" is any metal
container big enough to cover the pot(s). It must be intact, with no
holes. (Plug any with clay.) First, lay down a layer of sand about 4
inches deep. Next, lay down a layer of sawdust, 50/50 fine and coarse,
depending on type used. Softwoods are best. Set posts or bricks
solidly so they won't fall over, so they clear the sawdust about 2-3
inches. Place pots on the posts. Cover the pots with your washtub,
garbage can, etc. Seal the edge of the can with more sand and sawdust.
Make sure you have sawdust surrounding the can. Prop a layer of finely
split softwood (like pine scrap) all around the can. Sprinkle a small
amount of flammable onto the pine, like charcoal starter. You want all
the wood to burn evenly all around the can, and quickly. Set afire so
all begins at once. (We used a torch to quickly set it all around the
can.) You want it to burn hot and fast, and be finished burning in no
more than about 20 minutes. Once the burn is done, and don't wait for
ashes to cool, pull the hot materials away from the can rim. Using
safety gloves and being really careful, gently lift one edge a little.
You should see and hear air sucked into the can. Then remove the can
from the work. When it has cooled sufficiently, wipe each piece clean
with a soft cloth. For furthur shine, you can rub oil (olive,
vegetable, skin, etc.) onto the pot, and buff with a soft cloth. You
will lose some pieces due to thermal shock, but you must shock the
pieces to freeze the black. (I'm told the carbon is trapped by the
temperature change.) I've done this with commercial stoneware, and
locally dug clay. Add grog to the clay, and make the pots thin. Thick
walls seem to crack/break easier. I can't sugggest what to use for
metallic luster, but a few pieces sometimes get an area of rainbow
luster during the firing.
C. A. Sanger
ShardRock Clay Studio
Kansas, USA
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