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Soda firing is another form of atmospheric firing. Very late in the firing close to the final firing temperature of Cone 10 (2350 F), a mixture of sodium carbonate (soda ash) and/or sodium bicarbonate (baking soda) and water is sprayed into the kiln. The soda vaporizes and travels through the kiln carried by the propulsion of the sprayer and then taken up by the flames and ventilation of the kiln. The sodium combines with the silica in the clay to form a basic glaze. The sodium also reacts with other materials such as iron, copper, cobalt and alumina to produce different colors or “flashing”. The soda will also interact with glazes causing them to change as well.
Wow, there’s a lot going on in that kiln chamber! Why do I love soda firing? Just like with reduction firing but even more so with soda firing, I feel that the kiln is my partner in the creation of the pots. Unlike an electric kiln where it serves a single purpose of heating, the soda kiln is not just heating but also decorating and creating. The firing is very interactive and through skill and experience I do my best to set the kiln up to do its best work. But ultimately, the kiln will have the final say on the ultimate look of the finished pots. It’s all about control and letting go of it. Life right? Each piece is unique and is a testament, a legacy of the soda rich flame’s travels through the kiln.