Chester Nealie's kiln 4

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Flame observation port. Chester calls this a “spyhole”, and recommends an internal diameter of 30 mm for the hole. He says that if the port is too close to the firebox then it will suck air in rather than providing a flame out during reduction.

Damper at chimney base. The damper is nearly closed at the start of the firing to “steam the pots”. It is rarely adjusted during the firing and is usually set at 27 square inches cross sectional area. No passive damper is used.

At right: Chester indicates function of the flame observation port as seen from the stoker's position. Note the top of the chimney visible through the triangular window.

The amount of flame rising from the observation port is used as an indication of when to stoke but this cue has to be periodically recalibrated according to the stage of the firing and the damper setting.

Chester's firing procedure
In conversation with Chester in July 2003 I asked him about using this kiln.
The wood is from the property and collecting and splitting it is one of Chester's main activities. Black Cypress (Callitris calcarata) is used for 80% of total amount of wood, and all of the side stoking. It is split for side stoking. Some Cypress bark is used for stoking. Some Angophera (which has ash which is “fluffy”) and Stringybark (a Eucalypt) is used, and at the start Chester uses Yellow Box (Eucalyptus meliodora). The latter is used prior to the kiln reaching 600 or 700C. It is stoked through the lower firebox door, in pieces the thickness of a forearm.

Packing the kiln
The main chamber is referred to as the anagama chamber and is used for natural ash effects. In this chamber Chester uses tumble stacking. That is to say the pots are stacked in heaps at various orientations and are separated by ash resistant wads so they do not weld together and so that the wad marks are major decorative elements. Pots are frequently refired in different orientations so Chester's pots are difficult to read in terms of flame direction and ash impingement. Direct stoking onto pots occurs near the side stoke ports. Silicon carbide kiln shelves are used in the salt chamber to allow more conventional placement of pots.
Pots are fired raw, for a total of 50 hours, for 24 of which the main chamber is at top temperature. Absolutely no oxidation is allowed during the up cycle. Chester regards this kiln as firing hot with lots of ash so that the shorter firing time is acceptable to him. At the base of the chimney the pots reach cone 10, the salt chamber goes to about cone 10, and the small chamber to between cones 8 and 9. Three times during the firing, when the main chamber is at at least cone 9, the embers are allowed to build up in the main firebox and are then flicked onto the pots with an iron tool. Except on these occasions the ember bed height is controlled by the size of the mouse hole opening .The side stoke embers are built up and burned down twice during the firing. Chester plans to build a bigger anagama type kiln to be fired slowly to a lower temperature. He intends to use high firing terracotta clay in cooler parts and and aims to achieve lots of side stoke effects.
The rear chamber is salted, and after salting charcoal is introduced around the pots for local reduction. Salt is thrown in from the hand. The pots in the anagama chamber are downwind from the salt vapours and so are not salted. To raise the temperature at the bottom of the salt chamber the damper is opened. Closing the damper tends to raise the temperature at the top of this chamber.
End game
Chester uses final stage reduction with natural cooling. With damper still at the standard 27 sq ins opening, the firebox is filled “moderately full” with wood and the side stoke ports filled, and the doors closed and sealed (with leaks). The damper is gradually closed according to “back pressure” and flame at the chimney. Reduction persists for about an hour, then the damper is closed off completely.
Cooling time
The kiln is opened on the third day after the firing.
On the topic of clay bodies Chester makes the heroic assertion:
“Most Australian clays are just bloody awful – they don't flash”
This is followed by a qualification: “At least the ones around here don't”
This is still a major claim as on the way to Chester's place you pass the turn-off to Puggoon, a famous source of clay. Nepheline syenite type glazes and red flashing and other slips are used in the main chamber and Chester also makes use of a New Zealand slab clay with feldspar nodules.

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