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Christine Homer Weaving

Firing Methods and Results
 Firing Details
 Salt Glazing & Wood Firing
 

 Deterioration
of
Kiln & Kiln Furniture when Salt Glazing

The process of salt glazing is hard on a potter's kiln, the posts and kiln shelves used in the salt firing.

Salt glazing shortens the life span of a kiln.  A salt kiln may only last 1/5  as long, as a kiln in which sodium is not used.

Potters who use only a small amount of sodium or salt will experience a far lesser degree of deterioration to their kilns.  Robert chooses to use a larger concentration of sodium when firing, to achieve the fluid salt glazes he seeks.  He pays the price for that glaze look in the extra maintenance needed to keep his kilns in good repair.

When choosing to salt glaze, much time is required to care for the kiln and kiln furniture.  This time is not obvious to customers or potters who are unfamiliar with the technique.  It takes Robert about 18 hours to do maintenance on his wood-salt kiln after each firing.  Most of that time is cleaning salt and ash glaze build up from the floors, bag walls, and the one hundred Kiln Shelves used in his large Noborigama.

Salt Glazing - Hidden Costs

The Diamond Cup, which costs about $85,  is worn out after cleaning the furniture from one large kiln firing.  The clean up after each firing also consumes one of the "Wire Rope Brush Cup's" which cost about $45 each.

Above photo shows:  Kiln Shelf before Grinding

The Diamond Cup is shown on this Grinder, it is a grand tool for removing hard salt glaze buildup.  Another attachment,  the "Wire Rope Brush Cup" , visible in the bottom middle photo at right, works faster on light corrosion  
 It is necessary to wear a Dust Mask, Gloves and Face Shield when grinding.

An Angle Grinder is an excellent tool for removing salt glazed kiln wash and other corroded surfaces.  The "Segmented Diamond Cup" used on this grinder is best for hard to remove glazed areas.

Robert glues wads to pots in the wood and salt chambers of his Noborigama.  This large kiln consumes 1500 pots, and each piece will require between 3 to 8 wads. Over 6000 wads are made and  glued to his pots when loading, adding nearly a day of work just to do all the wadding.

Wash & Wadding = Hidden Costs

To re-wash the kiln shelves, floor, and caps of the bag walls, consumes about 8 Gallons of Kilns Wash, and 50 lbs of wadding in each firing of Robert's large Noborigama.

Every wood and salt firing is bound to have a few mishaps, but they can be kept to a minimum when the kiln is stacked with care.

If you fire enough pots, accidents are bound to happen.  The glaze fused the bowls together, breaking them apart,
 destroyed both pieces.

Tip Over's

The wadding on the Pilgrim Flask (middle of photo) shifted in the firing,
 resulting in the pot "kissing" the adjacent kiln shelf.

 It is important to apply a solid base of wadding, to prevent this kind of mishap.
The number, size and placement of wadding, will make the difference between success and failure.

The wadding supporting the Light Blue "Pilgrim Pot" on the left
 settled during firing, tipping it slightly and fusing it to the red pilgrim.

Quality of Bricks
The ceiling bricks in the salt chambers are of two different compositions. The wider arch bricks have a higher Silica Content and have glassed over earlier, than other "higher alumina" bricks.  This photo was taken after four salt firings, and the walls and arch are already well coated.

Most bricks used in a salt kiln are rated as "super duty" which is roughly equivalent to 42% Alumina.  The High Heat Bricks used by most potters to build kilns are rated at 34% Alumina.

The Firebox of the salt chamber is the most heavily impacted area since this is where the "salt burritos" are introduced to the kiln.