"... Gesalzene 1300°C"

Firing

Packing of the kiln starts in the chimney. To get the most out of the kiln after the 36-hours firing they try to use every available space for pots. As temperatures do not rise so high and not much salt reaches here the chimney is packed with strawberry pots, which should stay porous, flower boxes and planters.

Every piece is checked for cracks before stacking. The planters are packed into each other using highly grogged clay rings. The pots are only able to withstand the weight of the stack if the pressure is distributed evenly. Therefore Eberhard spreads sand on top and underneath every ring. This also helps to counter the shrinkage of the pots during firing. Bowl on bowl is stacked this way right to the ceiling.

Huge piles of green pots are stored on the floor above the kiln. The selected pots are handed down and stacked rim to rim in the kiln.

Here are some segments of columns and spheres for garden design drying on the kiln.

Test rings and cones are placed when the spyhole on the back is reached. They are the only means for temperature control.

Question: How old is this kiln?
Eberhard:" It has been constructed about 20 years ago."
Q.: Did you join the construction?
E.:" Yes, indeed. A mason came from Finsterwalde, but he never before had constructed a kiln ... he tried to learn from the others and started work. Without any support forms. He started here in the back and on the sides and then proceeded by estimation. A little mistake happened here in the front. When he starts the wall already with a slope he gets a bad arch curvature. The first rows have to be straight up, then the arch is rounded.
Q.: You produced your own bricks for the kiln?
E.: "No, these are heavy firebricks which have been delivered."

The bagwall is placed in the end.

After two days packing Eberhard closes the kiln door. He bricks it up, because this huge opening does not allow a door construction. A very sandy clay mortar is used for laying the bricks and sealing the door. This mortar has a low shrinkage and can be removed easily for uncracking.

Finally the upper firehole is closed. Ready for starting the fire.

A small fire in the ashpit heats the kiln carefully to 100°C within two days. The remaining water is driven out of pots and bricks in that time. Hot flames still have a reasonable distance to the first stacks.

These two days are calm and the best opportunity to store the firewood at the kiln. 15 cu.meter of pine are consumed during firing. It should have been dried for almost two years.

After the preheating is finished the ashpit is covered and Christel now stokes the grate in the lower firemouth to increase temperature. A hanging door prevents cold air from rushing in.

Steady stoking starts now - first every hour, but in the final stages every three minutes. Black smoke leaves the chimney everytime the firebox is filled. Temperature rises to 1000°C within 12 hours.

The stokers in front of the kiln now are dressed in thick cloth for protection and the stoking cycles get shorter. The pauses are just long enough for catching a deep breath. Slowly also the pots in the back start to glow. Flames lick on cones and the ware.

Eberhard fires the kiln since dawn . The upper firemouth has been cracked open and functions as a gas producer firebox for reaching higher temperatures. The wood does not burn down totally. A part is degased on the grate, then the gases mixes with air from the upper firemouth and combustion takes place already in the stacking area. The coal bed is rising to the upper firehole. Stoking is now performed nearly without interruption and the stock of firewood diminuishes.

The firing is now a struggle for every degree of temperature.

After two days candling and 35 hours of firing the climax is reached: cone 10 has melted and the glaze on the test rings too. Salting has to start now. But as the draft of the chimney would pull the salt out of the kiln much too fast, Eberhard opens up a hole in the chimney to reduce the draft. Christel salts the kiln through the firemouth. The sodium of the salt combines with the clay to a durable glaze.

A white cloud of hydrochloric acid leaving the chimney is an indicator for the chemical reaction. The spyhole on back of the kiln is salted too.

All openings have to be sealed now with mortar. The kiln cools down for a week before uncracking.

camera: Gerhard Meidinger / director: Mani Tille / sound: Jens-Peter Planke / speaker: Peter Veit / music: Martin Spies / cutttin&mixing: Gerhard Meidinger
produced in march 1991 / pottery Christel Kiesel / Crinitz(Brandenburg)
with Christel Kiesel and Eberhard Tunsch
a Kalkspatz e.V. production © 1992