John Baymore at River Bend Pottery

River Bend Pottery   © 1995 - 2011 All Rights reserved

 

 

JOHN’S NOBORIGAMA

The fire, which is at this point built directly on the floor of the main firebox, is slowly increased in intensity, always with the mind to the effects this increase is having on each of the five chambers of wares.  The complexity of firing this style of kiln is enormous.  In effect, you re firing five kilns at once, all with inter-relating controls and effects on each other.  Fire too fast and you can create rain in the last chamber!  Burn too much wood relative to the airflow at the wrong time, and you can cause massive firing defects in another chamber.

 

As the temperature gradually climbs in the first main chamber, successive chambers are also monitored so that they are firing correctly,  As more heat energy is required, the fire is moved off the main firebox floor and up onto a grate structure to allow better combustion.  Air ports are opened and closed as needed to maintain proper conditions of the fire in each chamber.  The type and size of the pieces of wood being stoked is constantly being varied based upon the condition of the fire in the kiln.  Eventually, after about 24 hours of continuous and careful stoking, the first main chamber has reached  approximately 2400 °F, and the wares there are finished.

 

Stoking on this main firebox then ceases, and the stoking operation moves to the stoke hole on the side of the kiln that allows wood to go into the firebox in chamber number two.  Great care must be exercised so as to hold the kiln back at this point.  Slight inattention can result in a very rapid temperature rise, ruining the wares.  As the coals in the main firebox burn off, the stoking ports and air inlets into this area are carefully sealed off with clay.  After about 3 to 4 hours of stoking in chamber number two, the chamber is completed.

 

The process is then continued along up the hillside, until all chambers are completed. The kiln is then sealed, and an exhausted John can go to bed.

MORE

The slow 10 hour overnight pre-heat on the small propane burner brings the main firebox and first chamber up to about 350 °F.  This time is used for a good night’s sleep before the real sustained and hot work of the wood firing begins.  Typically the kiln is shifted over from the gas pilot burner to a low wood fire at about 5 AM.  By then steam is coming off of the first chamber.