Nils Lou on sat 20 mar 10
I was introduced to glaze calc. by Glenn Nelson who taught at Univ. of =3D
Minnesota,
Duluth branch in the 50's. He wrote a seminal book, "Ceramics" which =3D
included an
indepth chapter on calculating glazes from recipe to empirical ratios =3D
and back.
I think at the time I did the calculations with a slide rule. And, I =3D
have one of his
original, spiral bound texts that eventually made it to the fancy =3D
publisher's.
So, to arrive at an empirical formula for a cone ten glaze I calculate =3D
one by choosing one=3D20
or more known C 10 glazes and averaging them. With that ratio of =3D
RO:R2O3:RO2 it is
then the basis for converting to a recipe that will fit using the clays, =
=3D
fluxes I may
want to play with. In the case of Moss Crystalou I wanted to emphasize =3D
lithium as a=3D20
principle flux as it has a propensity for crystallization. In Hawai'i, I =
=3D
had the opportunity
to study with Herb Sanders working with crystal glazes. Lithium was one =3D
of the more
interesting ingredients we played with.=3D20
Your question about temperature sensitivity I should have explained =3D
better. I mean, simply,
that this particular glaze has distinctly different characteristics on a =
=3D
vertical surface, depending,
I think on some complex factors such as wall thickness variations, =3D
gravity, and temperature
differentiation in the vertical span of the pot. As for testing on flat =3D
tiles I prefer to test
on vertical surfaces, so I have no information on that. I offer this to =3D
the group with the caveat
that it will work on some clay bodies, but not on others. Just like many =
=3D
others in our arsenal.
I have several examples of bottles and vases, all grolleg porcelain, =3D
made in the 70's that are
still unchanged, unshivered and fun to examine. I can post jpegs if =3D
there is any interest. It might
be easier to just try it out for yourself. nl=3D20
nils lou, professor of art
http://nilslou.blogspot.com
www.tinyurl.com/bpc5nm
503.883.2274
"Play is the essence of creativity", and
"What is not brought forward into consciousness....
we later call Fate", Carl Jung
ivor & olive lewis on sun 21 mar 10
Dear Nils Lou,
I understand perfectly.
As my mentor Dr Jim Cairney explained to me a long time ago when he
introduced me to the term "Empirical", and I asked for clarification, he
told me the question being asked is treated like it was a Lemon. You suck i=
t
and see ! You take an idea and play with it.
Round about 1984-5 I enjoyed an exchange of information with Glen. His book
is one I treasure. "Glazes for Special Effects" was another book I bought
early in my teaching career.
Sincere regards,
Ivor Lewis,
Redhill,
South Australia
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