contact@allblognow.comLogin
all blog now

July 12, 2023

Wood Fired Pottery and the Kiln

wood fired pottery

Wood fired pottery has a captivating relationship with its surroundings in a kiln. Ash, salts and minerals interact with every piece during firing to produce unique textured effects and one-of-a-kind textures that become part of its unique identity.

To successfully fire an urban setting, it is necessary to separate pots and fuel sources through stacking "cover sherds".

The Basics

Although each wood firing can vary greatly due to the nature of its kiln and type and amount of fuel used, there are certain general principles which apply to any wood-fueled kiln. Such factors include structure of the kiln itself, how tightly pots are packed in and choice of clay for making pots all play an integral part in producing final results.

As the fire burns, its flames transform the atmosphere within a kiln into an ever-evolving canvas of fire and fly ash particles, with heavier ones landing on pieces closer to the fire while lighter ash drifting through the flue area of the kiln and becoming part of its natural ash glaze. These effects give each piece unique texture and character while flame movement through the kiln creates flashing and texturing effects which further define its surface appearance.

Wadding is an integral component of firing pottery. As a refractory material made up of many different materials, wadding has long been debated among potters as to its role in creating beautiful firing surfaces. Simon Levin has developed an intricate system for wadding his Noborigama kiln which blends art and science, read his article Wadding for Wood Firing for more details, or watch this YouTube video about the Noborigama's firing process on YouTube for more insight.

Materials

Wood firing is an intensive ceramic process requiring extensive effort, time, and constant attention. Unpredictable in its results, this approach relies upon hot wood ash to interact with clay surfaces at extreme temperatures to achieve unique surface effects that lend their pots an organic appearance.

Different kinds of wood fuel the fire when creating pottery, each type producing distinctive effects on its final result. Hardwoods such as walnut, cherry and maple produce more distinctive colors and markings while pine and cedar yield subtler results. Furthermore, the type and size of kiln also plays an integral part in shaping its final appearance; an anagama kiln with chimney on one side and fire chamber on the other is capable of creating incredible wood ash effects in particular.

Wadding, an 80/20 blend of EPK kaolin and alumina hydrate that elevates clay bodies off of kiln shelves during atmospheric firings; and fly ash (a mineral byproduct from burning wood that contains extremely small particle sizes), are other materials commonly employed during wood firing processes. Wood fired potters may opt to glaze their pieces or leave their pieces without glaze entirely and rely solely on natural markings from firing for decoration.

Preparation

Wood fired potters must be thoroughly prepared before firing their kiln. Prep can take as much as one month of planning and preparation; there are many types of kilns, from small raku kilns to larger anagama kilns; each presents unique challenges and rewards.

A raku kiln is the go-to choice when it comes to ceramics. Its key feature is being small enough for potters to control and direct flames using wood wadding over their pieces, creating beautiful flashing patterns on her work by collecting wood ash which melts as the pottery heats up, adding additional decoration as it gives each piece its unique glaze.

A raku potter must be extremely careful with their placement of wood wadding, as too much could cause their piece to stick and not release from its shelf, while too little would prevent flames from reaching it for flashing marks. Unwashed wood ash contains trace metals which could affect its color as glaze; so the potter must carefully sieve theirs into clay with minimal amounts of Gerstley borate and silica for best results without adding metallic hues that interfere with desired finishes.

Firing

Firing a wood fire kiln requires an elaborate ritual: gathering wood, loading pots, stacking them securely on shelves, and then maintaining heat for extended periods. Each person approaches this task differently but there are similarities in how we all go about firing one; it requires physical effort as well as attention to various details that need careful management.

Protecting pottery from fuel requires isolating it from direct contact with coals by covering it with something such as sawdust. Some potters create their own wadding by mixing half whiting and half plaster of Paris and pressing into shape before saving for firing; other use pre-made refractory material, like expanded shale or even large cans bought from hardware stores as protective cover.

Wood firing creates stunning results; its combination of ash, salts and minerals with clay produces varied outcomes that range from crusty surfaces near the fire to less altered pieces in the back of the kiln. Furthermore, its atmosphere can also be altered depending on which wood was used during firing as well as where any stoke holes are situated in its chamber.