Alternative Firing Methods

Pit firing, Raku, Salt firing, Anagama, Gas firing

Pit Firing

Pit firing is probably the oldest method of firing   A pit is dug in the ground and layered up from the bottom Fired only once, the pots are porous and not water-tight

All topped by corrugated metal 5.then wood 4.then cow dung 3.then crumpled newspaper 2.then pottery 1.First is sawdust

Cross Section or Worms Eye View: Side View

Cross Section or Worms Eye View: Front View

or organic materials which Pieces can be bound with metal wire or organic materials which will result in trails and variations of color. This piece is wrapped in newspaper and bailing wire. It is now ready to go into the pit.

After the fire is lit sheets of corrugated metal are placed side by side over the pit. This slows down the firing and creates a good environment for sustained heat.

A steel rod and cinder block prying the corrugated steel upwards creates a flue.

Pit fired pottery

Raku

“Raku” means "joy" or "happiness". Raku started in Japan in the 16th century by Korean potters under Japanese rule Raku is linked to  Zen Buddhism, and the Japanese Tea Ceremony.  

Glaze is applied to bisque ware

Tongs are used to remove pots from the kiln at their maximum temperature.

Glowing hot pots are placed in metal drums filled with sawdust. Carbon from the smokes gets into the cracks caused by thermal shock

After pots are doused in water they are scrubbed clean Crackle lines remain

Due to the cracks, raku ware is not watertight They are valued as beautiful, decorative objects

Salt Firing

Salt, or sodium chloride, is introduced into a hot kiln Salt firing started in Germany in the 15th C.   Salt, or sodium chloride, is introduced into a hot kiln when the temperature reaches 2350 F. or higher. Sodium combines with silica on the surface of pots creating an “orange peel” effect.

Salt becomes an active vapor through the kiln A diluted form of hydrochloric acid is released as a vapor Salt fired kilns can not be used for other kinds of firing.

Salt fired pottery

A Japanese term meaning "cave kiln" Anagama Firing

Storage jar by Carol Rosser Fired in an anagama for 84 hrs. with Blackwood and Forest Red Gum

Carol and Arthur Rosser Anagama plan Side view Top view

The fire box is stoked every ten minutes for about 3 days.  Ash must be raked regularly from the mouse hole so that the ember bed is kept alive

Stoking one of the front side stoking ports.

Generic design of an anagama kiln Chim- ney, 3m high 5. Flue 1. Door Cast arch, made of heat resistant cement Dampers, two – One for firing, the second to tightly shut the flue Stacking floor of silica and sand for placing unfired pots 2. Firebox

Gas Firing

Melting pyrometric cones determine temperature levels

Flames come out of every opening, unless they are plugged

A load of copper red glazes (in the center of the kiln) indicates a variation in reduction between front and rear.

Gas reduction firing uses a fuel such as natural gas or propane. The temperatures of a gas fired reduction kiln may exceed 2300F., Cone 10 Gas is a combustible fuel and  the potter can control the ratio of oxygen to gas during firing. 

Depriving the kiln of oxygen creates a “reduction” atmosphere, where carbon monoxide can be produced. This only occurs in gas fired kilns. Burning of chemically combined oxygen in the clay and glaze minerals gives reduction fired pottery its unique characteristics and rich colors