Published Oct 20, 2021
I can get lost in the sumptuous surfaces of Gail Nichols’ soda fired work. The way she skillfully “paints” her pots through the atmospheric firing process is fascinating and the results are breathtaking–from the rich dimpled textures to her trademark “soda ice” blue hues. Though I have never participated in a soda firing, it rose to the top of my “must do list” after reading Nichols’ book, Soda, Clay and Fire. Now, I just need to find someone willing to share their soda kiln (sigh). In today’s feature, we bring you a couple of Gail Nichols’ recipes and techniques for soda firing.–Jennifer Poellot Harnetty, editor.
Please note: The following techniques and recipes are for fuel burning kilns and should not be used in electric kilns.
Soda glazing was once hailed as an alternative to salt glazing, but has proven to be much more than that. The choice of vapor glazing is now primarily one of aesthetics, with soda’s potential extending far beyond that of imitation salt. A contemporary challenge is to explore what soda has to offer in its own right, and to set aesthetic directions for this new ceramic process.
For the Gail Nichols Soda Mix, add 9 U.S. fl. oz. of water per 1 lb. (600 ml of water per 1 kg) of dry mix. Wearing gloves, mix the dry ingredients thoroughly, then add the water all at once. Stir until the mixture begins to set, then break it into small pieces.
Light soda ash is required for the setting process. A wet mixture of sodium bicarbonate (baking soda) and calcium carbonate will not set; neither will a mixture using dense soda ash. Sodium bicarbonate is not an essential part of the soda source, but it makes the wet mixture less caustic. Sodium bicarbonate is also inexpensive and readily available in the supermarket or from a bakers’ supplier.
As this mixture breaks down in the heat of the flame, water vapor is released along with the vaporizing soda. Water vapor helps to carry the soda through the kiln chamber, enabling good glaze distribution and evidence of flame movement on the work. Water vapor also appears to assist with soda dissociation and glaze formation.
The choice of kaolin used in the Basic Soda Slip largely determines the color of the fired surface. Soda glaze quality is highly reliant on materials used, especially clay. It is important to become familiar with locally available clays and their responses to soda vapor. Developing and working with slips is a good place to start with such research.
HEALTH AND SAFETY PRECAUTIONS
Soda ash dust is an irritant to the nose, throat, and lungs. In combination with lime, it will form sodium hydroxide (caustic soda), which can cause alkaline burns. Wear impervious rubber gloves and a NIOSH (National Institutes for Occupational Safety and Health) approved respirator mask. Chemical safety goggles are recommended for eye protection, and long sleeves and trousers should be worn. These precautions apply to all preparation and handling stages for the calcium/sodium mix, including handling the firebox residue, which is high in sodium hydroxide.