In the Soda Zone Mark Bollwinkel

Our firing group conducted an experiment to introduce soda into one segment of a kiln rather than dedicating an entire chamber to it. We fire a small wood kiln with a 50-cubic-foot cross-draft chamber. This chamber has an “in-chamber” firebox in the front and one stoke hole in the middle that helps fire off the back half of the kiln.

Two-foot-long pieces of 2-inch tree bark covered with a soda paste were introduced in the rear stoke hole, beginning at Cone 8 and continuing every 15 minutes until Cone 10 was reached. The draft carried soda vapor through the bottom and rear quarter of the kiln and then out of the chimney, not affecting the other parts of the kiln. We call this area our “soda zone.” We gained effective distribution of soda in the zone with excellent traditional firing results in the rest of the chamber. The placement of the soda-bearing wood must be done with caution as direct contact between the paste and a pot leaves a permanent scar. Soda does make a mess of the kiln floor and shelves, so we lay a bed of oyster shells in and around the zone floor, which seems to help in clean up.

The piece to the right is one of the many examples of beautiful work by soda firing expert Gail Nichols, featured in her book Soda, Clay and Fire.

**First published in 2008.