Process-Soda and Fire

My work may be completely made on the potters’ wheel or it may grow from parts made on the wheel.  The bowls and cups portray my appreciation for the symmetry achieved by using the wheel. The undulating sides of the trays display a more organic feeling.  The altered plates and mirror frames demonstrate a little of both.   Decorative inspiration comes from my love of the natural environment and interest in Asian art.   Some of the work is decorated with brushwork using slips; some is incised with designs influenced by Asian brushwork; the rest is left for decoration at the time of glazing.  All have multiple layers of glaze applied.  

After the work has dried, there is  an initial firing called the bisque firing. This firing partially vitrifies the work but leaves it porous  enough so that any applied glazes will be absorbed.  The work is then glazed and wadded.  Wadding refers to the little soft balls of a mixture of clay, alumina and water that are glued to the bottom of all the pots.  These are necessary to prevent the pots from sticking to the kiln shelves during the glaze firing.  At this point the work is ready to be loaded into the kiln.waddedplates3x5150

Plates with wadding attached.

A fuel-burning kiln is used in soda firing.  Generally the fuels used are wood, gas, or oil.  The kiln used for this work is gas fueled and is fired to approximately 2300 degrees Fahrenheit.  It has a pyrometer that measures the temperature. Because this kiln has no computer to control temperature climb, pyrometric cones are placed inside the kiln where they can be visually monitored during the firing. These cones monitor “heat work”. They are made of materials calibrated to melt after a certain amount of time at a certain temperature.  During the firing the potter uses the pyrometer and the cones as guides for making changes in the fuel to air ratio.  These changes affect the glazes and clay body color as well as control the temperature climb of kiln.


Unfired cone pack (left)   Fired cone pack (right)

Towards the end of the firing, a liquid solution of soda ash and water is sprayed in through ports in the kiln.  On un-glazed pots, this solution creates a glaze as it interacts with the clay.  In fact, most potters leave some of the clay body purposefully bare in order to take advantage of this wonderful blush of color.

 The soda solution also creates unique effects on glazed surfaces. Because fuel-burning kilns have a flame that travels around and through the firing chamber, the soda ash solution is also carried along with the current of the flame.  Thus, the results are very much determined by placement of the work in the kiln. Two cups glazed in the same glaze can come out very differently depending on where they are in the kiln. This results in work that is very unique and distinctive.


Soda ash solution being sprayed into the kiln.


Kiln load of work ready to be unloaded

© Hathaway Ceramics 2011-2015