The Journal of Australian Ceramics Vol 49 No 1 April 2010

Focus: Wood-Fi ring
Janna Ferris with completed glaze pack tor first firing,
showing offvset shelving arrangement, air inlet ports and
fire box; photo: Yun Wiedenhofer
to use it. Ferris works with oxidised, high-fired
earthenware, often with underglaze decoration.
I perceived my long-dreamt-of lustre kiln.
The materials were on hand, having long
been collected or saved. Dense firebrick was
used in the firebox and partially up the rear
wall, the floor, flues and chimney. The chamber
was constructed using light, insulating brick,
backed with fibreboard taken from a derelict old
gas kiln (its last firing prepared blanks for the
lustre workshop!). Braided rope, emerging as
coils from an old dusty box, insulated the roof;
ash and perlite filled any voids, and the whole
construction was encased in salvaged, partially
fired, adobe brick.
The firebox beneath the chamber throws a fan
of flames up the rear wall, pushing through the
setting; flames surge down through front corner
exits and back along the outside of a single brick firebox, exchanging heat and converging into the
chimney. A four-brick passive damper gives rear access to flues, rubble floors topped-up or raked lower,
another passive damper positioned several courses higher. A round masonry chimney tapers to a height
where a metal flue and spark arrester safely intervene. The firebox mouth is sliced shut with a counterbalanced,
tin guillotine.
A key feature is the front air inlets into the flue-channels, entering just below where flames and gases
exit the chamber. Their uses are manifold. As passive dampers, they throw up air curtains, partially
circumventing the chamber from the chimney to encourage reduction. As air intakes, exhaust gases
oxygenate while passing over the hot exterior of the firebox, ensuring a clean post-chamber burn. They
are also important for judging the volume and quality of fire leaving the chamber: a fire guide to firing.
The chimney shows reluctance to display plumage of billowy flames and smoke.
To minimise ash effects, a perforated, curved bag wall is arranged around a diamond floor plan.
A heavy, silicon carbide shelf is positioned off-square, the rear corner to pierce incoming flames, the
opposing corner midway between floor exits. A clay bag wall straddles the rear corner and rests on the
brick floor. The arrangement places the setting well clear of exit flues, providing space for combustion
where gases enter, split and mix and allows some flame passage under the floor shelf. The stack finds its
optimal position within the cube.
Of three earthenware firings Ferris has completed, each has been rather different. An opportunity
taken to tidy the yard meant the first fired much like an incinerator, consuming mostly timber off-cuts
and degraded hardwood. Some pots were marred, but generally the work offered subdued colour and
gently lustrous surfaces - a window to further possibilities. I loved the look, but, as w ith all wood firing,
the results didn't quite match expectations. Glazes were not the full gloss finish anticipated, appearing
under-fired, with some colours fugitive. A transition from electric firing to living wood-fire would not be
without a little angst.
Shields of paper-clay were then mounted on shelf perimeters to provide more protection. This second
S2 THE JOURNAL OF AUSTRALIAN CERAMICS APRIL 2010