David Hendley on wed 28 may 03
I design most of my glazes by manipulating unity molecular formulae.
Since I learned glaze calculation almost 30 years ago, I am completely
comfortable looking at a unity formula and having a good idea what
the glaze will look like.
Sometimes I have a mental idea of what I want a glaze to be and develop
a formula that should give the desired result, but often I am just
manipulating numbers, stretching certain elements up to, or past, the
normal limits, just to see what happens.
I know it's hard work to learn glaze calculation, but if you intend to be
a potter the knowledge gained is well worth the effort. It is so easy to
do the calculations in this age of computers, but there is still a lot to
learn about the contributions and behaviors of the different elements
and glaze materials.
In the old days, we were excited when inexpensive calculators came
on the scene, so we could toss out our slide rules. It took about 15
minutes to one glaze calculation. Now, even an outdated 286 computer
can do it in 1 millisecond!
For fine-tuning a glaze or developing colors, nothing beats a tri-axial
blend. I generally divide the tests into a triangle with 5 tests to a side,
for a total of 15 blends per test.
David Hendley
Maydelle, Texas
david@farmpots.com
http://www.farmpots.com
Louis Katz on thu 29 may 03
On Wednesday, May 28, 2003, at 10:08 PM, David Hendley wrote:
> I know it's hard work to learn glaze calculation,
I am not convinced that it has to be hard. I The "math" involved in
glaze calculation is as near to arithmetic you can get and still call
it math. It is conceptually no more complicated than what goes on in a
kitchen. The problems is in knowing your ingredients and knowing as
much as you can muster about unity formulae.
The instruction for glaze calculation in the old "Clay and Glazes" by
Rhodes was enough to learn by, but was not enough to learn it easily.
It has gotten easier as people have talked about the process more.
Louis
Paul Lewing on thu 29 may 03
on 5/28/03 7:08 PM, David Hendley at hendley@TYLER.NET wrote:
> I design most of my glazes by manipulating unity molecular formulae.
I'd like to second David's comment on this. This is how I go about
designing a glaze formula these days myself. And this is a big plug for
calculation software. I think I said on stage at NCECA when I was one of
the Glaze Doctors a year or so ago, that I would not have been up there on
that stage if I had not gotten calculation software about ten years earlier.
It's true that you still have to do the studying, the testing, and the
paying attention, but nothing I have found helps more than the software.
The last two glaze recipes I've invented, that I now use in production and
hand out at workshops, were envisioned first as molecular formulas, by
deciding on what flux balance I wanted, then deciding what SiO2:Al2O3 ratio
I wanted to determine what surface I liked, and then a recipe made of that
formula. One of them was exactly what I'd been looking for on the first
try, the other needed just one slight adjustment to be what I'd envisioned.
It works.
Paul Lewing, Seattle
Paul Lewing on fri 30 may 03
on 5/29/03 5:59 PM, Louis Katz at louis.katz@MAIL.TAMUCC.EDU wrote:
> The instruction for glaze calculation in the old "Clay and Glazes" by
> Rhodes was enough to learn by, but was not enough to learn it easily.
> It has gotten easier as people have talked about the process more.
Louis, it also got easier after people realized that there was a mistake in
the math in Rhodes' example in some of the earlier editions and it got
corrected. I remember trying to teach myself from his book a couple of
times and not being able to understand it. Then years later, after I'd
learned how to do it from other books, I went back through his book and
found the error. I don't know when it was corrected, but I bought my copy
of "Clay & Glazes For the Potter" about 1966.
Paul Lewing, Seattle
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