EWF Summer 2002 Workshop

Yohen Firing in Chamber 4

Having returned from presenting at the Aomori International Wood Fire Festival in Japan only one day before the beginning of the Earth, Water, and Fire workshop held at his home studio, John decided to share one of the techniques he learned about and utilized while firing the noborigama at the Kanayama Ceramic Cooperative in Goshogawara-shi.  This finishing technique, called "yohen" in Japanese, involves covering all of the unglazed wares stacked in the chamber with hardwood charcoal at the peak of the firing.  The crushed wood charcoal is allowed to burn off slowly, producing rich varied colorations on the wares which have already picked up deposits of flyash from the stoking of the wood that brought the chamber to the almost 2400 F completion temperature.

John showed the summer 2002 workshop participants pieces of pottery which he brought back from Japan that clearly documented the type of surfaces produced at Kanayama, and then the group discussed selecting the appropriate clay bodies and forms for the pieces that would be placed in the last, smallest chamber of the River Bend Pottery climbing kiln, "Kawagama".  

John copied the basic design of the charcoal shovel that would be fabricated for this firing from that used by Matsumiya Ryouji at Kanayama.  Potter / engineer Kurt Heinzman, who was participating in the summer workshop, immediately suggested a minor design change to the placement of the handle after watching a video of John putting charcoal into the Kanayama noborigama.  The revised design was finalized and the new shovel was constructed out of steel.  Once this design concept is proven in repeated use, a new shovel will be fabricated out of stainless steel.

The last chamber was loaded leaving space above each layer of pottery so that the special shovel could be passed above the ware.  This results in leaving a lot of empty open space in the stacking....... a "costly" procedure in a wood fired kiln where each cubic foot of heated chamber is won through lots of hot, sweaty labor.  A plunger design in the scoop part of the shovel allows the charcoal to be ejected onto the wares below without tipping the shovel.  Pieces or claywork were stacked in a "jumble stack" fashion in the chamber...... with pieces separated from each other by a "wadding" mixture of fireclay and sawdust.  When the kiln door was bricked up, special large ports were left through which the shovel could be inserted into the chamber.

When the chamber had reached almost 2400 F, at about hour 25 of stoking, the bottom shelf's charcoal port was opened up and, starting at the extreme back end of the chamber, shovel-full after shovel-full of charcoal was spread evenly onto and over the glowing wares.  The thick deposit of charcoal was worked forward until all the wares on the bottom level were covered with about 6 to 8 inches of burning charcoal chunks.  Then the port on that layer was closed and the procedure was started on the next layer of shelves.

As you might expect, this was a very hot business on a summer's day!  And at this point in the firing, everyone was pretty tired.  But the excitement of this new procedure helped to "revive" everyone a bit, at least for a little while.

The results of the yohen firing were wonderful and far exceeded John's expectations for the first time doing this in his kiln at home.  More detailed pictures of the results will be posted here soon.

Photos:  Kurt Heinzman and John Baymore

© 2002        J. Baymore     all rights reserved

Studio visits are welcome. Call 603-654-2752 to make sure I'm there.

This page last updated:

11/10/2002 03:29 PM

Free JavaScripts provided
by The JavaScript Source