Mark Potter on mon 12 jul 04
Salt added to Glazes or Clay
Dear Folks at ClayArt:
I hope this post gets through - lately I've been getting the feeling my
firm's email is blocked by Clayart due to the name - a sextant is a
nautical instrument, not a naughty instrument!!!
Anyway I have a bunch of questions for you Shino gurus:
I was recently out at Rodney Mott's legendary woodfiring of his "Big
Mama" kiln, in Penryn CA - (Woodstoke 2004). I have questions to you
knowledgeable wood-firers about some of my results.
PENN STATE SHINO?? HEARD OF IT??
My first question is about a shino glaze I used that now I'm having
trouble finding the recipe to. It is called "Penn State Shino"? Does
anyone at Clayart have it?
VERY UNUSUAL RESULTS
I used this Penn State Glaze over a number of cups, some of which were
coated with an iron rich clay slip. The cups came out a gorgeous red
brown, almost temoku or shaner's red in tone, not at all 'shino-ish' in
color. This happened to cups that did not receive much flashing or ash
deposition. This woodfiring produced some very heavy reduction (there
was even some carbon trapping in the firing) and parts of the kiln were
overfired. Loss rates were heavy. But some of the results were
HUGE RANGE OF COLORS FROM ONE GLAZE??
I'm new at wood firing but have done a lot of shino with gas. I cannot
account for the enormous variety of colors coming from this one shino
glaze. Greys to reds to yellows! So many factors to consider, a huge
range of temperatures within the kiln (probably 3-4 cones) the fact that
some parts of the kiln went to very high temperatures (Cone 12 anyway),
the cyclical way the kiln was fired - reduction to oxidation and back
(with each load of firewood) - the fact I elected to use a shino glaze I
was unfamiliar with .=20
. . Prior years the kiln was salted, but not this year . .=20
I also glazed a small white bottle with the same shino - and get this -
got a lovely yellow result. Yes yellow. Not pottery barn yellow, but a
rich yellow streaked with red and brown. I'm perplexed about what
happened. Ideas? I'll try and post pictures. Can Shino produce a yellow?
SEA SALT / SALT IN GLAZE RECIPES
My next question is about adding salt or sea salt to glaze recipes, or
even clay. What does this do, and what kind of changes can one expect to
see to glazes if you add salt to glaze or clay materials instead of
salting the kiln.