Atmospheric Firing Samples

What is wood firing? Wood firing in ceramics is a traditional technique where wood is the primary fuel source for firing pottery in a kiln. The process requires constant attention as wood must be manually fed into the kiln to keep the firing on schedule.  This method creates unique and often unpredictable surface effects on the pottery due to the high temperatures and the interaction of wood ash with the clay and glazes. This process is known for its unique and unpredictable effects on ceramic pieces, resulting in distinctive colors, textures. The work inside of a wood kiln is not only subject to the heat from the fire, but also to the shifting atmospheres of reduction and oxidation, variations in temperature, flame movement, and wood combustion mean that no two pieces in a wood firing will be exactly the same.

How does it work? During a wood firing, pieces of pottery are loaded into the kiln, and wood is burned in a firebox within the kiln. As the wood burns, it releases heat, flames, and ash. Wood ash builds up on any surface that it can find and eventually melts, creating a natural glaze. It requires careful attention to the firing process and a deep understanding of how different factors, such as wood type, kiln design, and temperature control, influence the final results. These firings can last anywhere from a few hours, to 10 or more days in length. 

What is soda firing? Soda firing is a type of atmospheric firing where sodium carbonate (Na2CO3) is introduced into the kiln at or near the peak temperature, 2350°F, and at high reduction of the firing (reduction fire starves the kiln of oxygen and produces intense earth tones). Sodium Bicarbonate, otherwise known as baking soda or soda ash, can be used as an alternative. The soda is basically a glaze, and when two glazes mix, they can react chemically with one another creating a variety of dynamic colors, textures, and surfaces, but also a lot of movement. No two pieces will be alike!

How does it work? When the soda ash is introduced, due to the intense heat, it vaporizes and becomes a flux (melter) and is carried throughout the kiln with the path of the flame. As it moves along, it begins to glaze the wares inside the kiln chamber as it is attracted to the silica within the clays, slips, and glazes. Ways of introducing soda into the kiln include spraying soda ash dissolved in water, dumping a solid mixture of soda ash into the fire box, or putting it on wood to be added to the kiln. When placing the pieces in the kiln during loading, you must think carefully about when and where you want a piece to get lots of soda, or when and where you want a piece to be more protected. The kiln must be evenly loaded because the flame will travel on the path of least resistance, and therefore the soda will also be traveling on that same path. You must be aware of how the piece is glazed. Pieces are wadded to help prevent wares from sticking to the kiln shelves. One side of a piece can look totally different than the other side, even if glazed the same, depending on how the soda hits the piece.