Dave Finkelnburg on wed 29 mar 00
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Clayarters,
For those of you with an interest in Shinos, I made the following notes
during the NCECA breakout session Friday afternoon.
Steve Loucks, from Jacksonville State University in Alabama led the
discussion. He began the session with a brief history of shinos. The point
was, the original glaze was likely all feldspar, possibly with some ash.
Current recipes use high soda feldspar and/or soda ash, and sometimes =
lithium,
because they melt at low temperature, and the low melting temperature traps
carbon. This also means to get good shinos you have to start reduction at =
a
low temperature, like around cone 014 to cone 010.
Steve attempted to de-emphasize Shino recipes. Shino is not so much a
particular recipe as a singular appearance--a deep, warm glaze typically =
high in
clay, which means lots of alumina and silica, but with fluxes which cause it=
to
melt very early in the firing process.
There was some discussion of single firing, basically to the point that
Malcolm Davis says single firing doesn't produce carbon trapping. He =
reasons
that the soda ash doesn't get distributed to the surface in the same way as =
with
bisque ware, so the early glaze coat doesn't form in single firing like it =
does
over bisque ware. He was in the group and said that was what he thought.
Malcolm said he spritz's pieces (hand spray bottle) with a saturated =
soda
ash solution to get some improved carbon trapping. He also said up to 5=25 =
salt
will give more lustrous shinos.
There seemed to be general agreement that spray application of shino =
glazes
is bad. It has so much clay it's too viscous to run, and the texture of the
glaze droplets tends to remain. Painting, dipping and pouring seem to be
preferred.
Regarding glaze layering, Malcolm said shino HAS to go on first. =
=22Shino
over is a curse,=22 he said. Again, because of the clay, anything coming =
out of
the glaze below breaks through the shino and it doesn't heal over, leaving a
pinhole. He said that might be okay, if that's what you wanted.
There was some suggestion of refiring shinos to a low bisque temperature=
if
they don't work the first time. That won't give you a great shino, but it =
may
salvage something useable.
Firing seems to be generally oxidation to cone 014 or so, then mild
reduction until the last 20 to 30 minutes, then strong oxidation at the =
finish.
Heavy reduction wasn't regarded as particularly effective. They cited Ron =
Roy's
suggestion that heavy reduction produced large particles of carbon, which he
said were probably too big to get inside the glaze surface to condense on =
the
clay body. One person said he fired fast to cone 10, then reduced down to =
get
shino effects, but there wasn't much support for that method, the consensus
being that the shino effects has been caused by reduction during the fast =
firing
up.
There was a comment that high iron clay bodies yield more shino results.
Jim Busby (James Busby jbusby=40linfield.edu ) , one of Nils Lou's =
grad
students at Linfield College, was also in the group. He is searching for =
Shino
recipes and would like to hear from you if you have a recipe you could =
share.
He handed out copies of some recipes he had collected for wood firing
I hope this gives you some idea of how the session went=21
Dave Finkelnburg
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