Skutt KilnMaster Kilns Manufactured between 2000 and 2006 - Manual (Page 19)

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Lusters. Luster may flake off if applied
thickly and will “frost” if overfired. To
start over, fire to 06-05. Keep ware well
away from kiln elements. Fire to 019 for
durability, drop to 020 if frost is encoun-
tered. Lusters are extremely sensitive to
contamination by kiln vapors, particularly
those from greens, and lid ventilating
must sometimes be continued at 1/2” or
1” throughout the firing.
Overglaze. Breakage of ware during over-
glaze firings can usually be traced to
roughly-handled, unevenly-dried or
unevenly-sponged greenware. In general,
there is less trouble with art porcelain than
with ceramic pieces, and least with high
quality, pre-glazed, dry-footed imported
china blanks.
Firing schedules for overglazes can usu-
ally be accelerated because the ware is
entirely free of moisture. A fast firing rate
will be appropriate for this type of ware.
The lid remains propped until the odor
from the burning medium is no longer
detected. Under-ventilation is the biggest
cause of problems. Of course, if you are
firing with an EnviroVent, this will not be
a concern.
Firing porcelain.
Art porcelain should be bisque fired to
Cone 5 or 6 (not 05-06) in your Skutt kiln
unless glaze is to be applied, in which case
a soft 05 or 06 non-vitrifying fire is appro-
priate. Ware should be loaded and sup-
ported as noted in the loading instruc-
tions. Begin lace fires with the lid posted
open 2 1/2”. Optimum quality can be
achieved several ways:
1. By not loading the kiln very heavily
with ware or extra shelves.
2. By bisque firing twice; one to the firing
temperature of the clay, and another to
one cone equivalent cooler. Wet-sand-
ing with a fine grit silicon carbide paper
between firings will maximize smooth-
ness in the finished piece.
3. “Soaking” for 30-45 minutes slightly
lower than the maturing temperature
will add sheen to the porcelain. The
process for soaking is discussed in the
section about glaze firing.
Porcelain glaze is usually fired to maturity
of the clay and dry-footing is still essential.
Overglaze decoration is fired exactly as
with ceramics, but usually 2 to 4 cones
hotter (017-015) to produce penetration,
gloss and durability on the higher-soften-
ing glaze. Overglazes are also frequently
applied directly to porcelain bisque that is
to remain unglazed. Fire to the above
cones.
Firing stoneware.
Most Skutt kilns (except a few 208V mod-
els and KM-614-3) can attain Cone 8 or
Cone 10. Because stoneware shapes are
designed for self-support during firing,
the glaze can be matured at the same time
as the body, particularly because the pin-
holes, sunbursts and scumming which
tend to accompany one-firing are often
highly prized in stoneware. Pieces are dry-
footed, of course, and loaded as previous-
ly described.
The procedure for stoneware differs
from that for one-fire ceramics in that the
plain or decorated greenware is usually
first given a low bisque firing to Cone 016-
04 before glazing. Due to the ware’s thick-
ness, the firing rate must be much slower
and more prolonged than in other types of
ware.
While the typical overglaze decorations
are rarely considered suitable on
stoneware, Cone 06-04 reds, oranges and
crackles are sometimes added after firing
to provide effects unobtainable at the
higher temperatures. Warm (130˚F/54˚C)
the vitrified ware to facilitate application
of glaze.