karen gringhuis on tue 7 oct 03
Ivor & anyone else -
>I have not read "the Cushing HANDBOOK" and there may
not be a copy in Australia in a public library.<
Point well taken - if you are in a school situation,
may I suggest adding one to it's library?
>Perhaps you could post a precis of what this is all
about on page 53 for those of us in foreign climes?<
See below.
>From the tenor of your note, you are proposing an
empiric approach based on direct trials with real
materials. If so, I would agree.<
First let me clarify - empiricism is not the issue
here. In my mind empiricism is the hands-on test
mixing and firing work which hopefully accompanies ANY
method of teaching glaze - be it Ian Currie's Four
Corners/Eutectic Trench approach or an approach built
upon the UMF.
Also let me state that I consider none of these
methods to be totally independent of or excluding any
other method. My thinking is just to keep glaze as
simple as possible for beginners and to minimize the
very real Fear Factor Kat talked about.
Precis of Val Cushing's "Constructing Your Own Cone 9
Base Glaze" from Cushing's HANDBOOK. After guiding
the reader thru the variables in deciding what type of
glaze is wanted (temp., surface texture, light
transmission, etc.), this chapter then has the reader
choose MATERIALS from each of several groups. The
materials are grouped as follows:
-- fluxes - spars, frits, auxiliary
-- materials causing satin to matt surfaces
-- glass former materials
-- clay content materials
-- optional opacifiers & colorants
The chapter then includes "clues, hints, suggestions"
as to approximate percentages from which group to
achieve general types of surfaces followed by
paragraphs on mixing a test batch and practicalities
such as putting the test on a cookie just in case.
My point in this discussion is that this group
structure organizes glaze materials - IMHO the first
step to understanding what is going on. It also
arranges them according to function with no apparent
chemistry or element symbols in sight. If students can
see the logic to this structure, then hopefully they
no longer view materials as one huge intimidating
indecipherable mass of strange words.
Using this organized group structure, students can mix
& fire a glaze getting empirical results to be
evaluated with fellow students & a knowledgeable
teacher. Hopefully this will lead to their own qns.
"why did...." & "well, what if I...."
The answers to their qns. should lead more serious
students toward a UMF structure and actual oxides
composing these materials.
Personal anecdote i.e. more than you wanted to know.
In a former life as a consumer market research
analyst, I presented statistical info to merchants.
The market research dept. was very highly respected,
second only to the company lawyers - meaning many
people could understand only half of what we were
saying! I considered my job well done when a question
from my audience was answered by another member of the
merchant audience - meaning someone "got it."
Glaze knowledge is the same way. In the face of
novices, if we cling to our JARGON, we will only scare
off students. The job of a teacher is to present
information in a way conducive to learning - and to
me, that demands remembering what it's like NOT to
know it.
=====
Karen Gringhuis
KG Pottery
Box 607 Alfred NY 14802
__________________________________
Do you Yahoo!?
The New Yahoo! Shopping - with improved product search
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iandol on wed 8 oct 03
Dear Karen,
Thank you providing that information. Your description of the "Cushing
Handbook Method" paraphrases what I started doing more than a couple
of decades ago with year eight students as an introduction to pottery.
Keeps things in the realms of what can be experienced.
Best regards,
Ivor Lewis. Redhill, South Australia
----- Original Message -----
From: "karen gringhuis"
To:
Cc:
Sent: Wednesday, 8 October 2003 2:17
Subject: The path to Glaze know how is way way too long
> Ivor & anyone else -
>
> >I have not read "the Cushing HANDBOOK" and there may
> not be a copy in Australia in a public library.<
>
> Point well taken - if you are in a school situation,
> may I suggest adding one to it's library?
>
> >Perhaps you could post a precis of what this is all
> about on page 53 for those of us in foreign climes?<
>
> See below.
>
> >From the tenor of your note, you are proposing an
> empiric approach based on direct trials with real
> materials. If so, I would agree.<
>
> First let me clarify - empiricism is not the issue
> here. In my mind empiricism is the hands-on test
> mixing and firing work which hopefully accompanies ANY
> method of teaching glaze - be it Ian Currie's Four
> Corners/Eutectic Trench approach or an approach built
> upon the UMF.
>
> Also let me state that I consider none of these
> methods to be totally independent of or excluding any
> other method. My thinking is just to keep glaze as
> simple as possible for beginners and to minimize the
> very real Fear Factor Kat talked about.
>
> Precis of Val Cushing's "Constructing Your Own Cone 9
> Base Glaze" from Cushing's HANDBOOK. After guiding
> the reader thru the variables in deciding what type of
> glaze is wanted (temp., surface texture, light
> transmission, etc.), this chapter then has the reader
> choose MATERIALS from each of several groups. The
> materials are grouped as follows:
> -- fluxes - spars, frits, auxiliary
> -- materials causing satin to matt surfaces
> -- glass former materials
> -- clay content materials
> -- optional opacifiers & colorants
> The chapter then includes "clues, hints, suggestions"
> as to approximate percentages from which group to
> achieve general types of surfaces followed by
> paragraphs on mixing a test batch and practicalities
> such as putting the test on a cookie just in case.
>
> My point in this discussion is that this group
> structure organizes glaze materials - IMHO the first
> step to understanding what is going on. It also
> arranges them according to function with no apparent
> chemistry or element symbols in sight. If students can
> see the logic to this structure, then hopefully they
> no longer view materials as one huge intimidating
> indecipherable mass of strange words.
>
> Using this organized group structure, students can mix
> & fire a glaze getting empirical results to be
> evaluated with fellow students & a knowledgeable
> teacher. Hopefully this will lead to their own qns.
> "why did...." & "well, what if I...."
>
> The answers to their qns. should lead more serious
> students toward a UMF structure and actual oxides
> composing these materials.
>
> Personal anecdote i.e. more than you wanted to know.
> In a former life as a consumer market research
> analyst, I presented statistical info to merchants.
> The market research dept. was very highly respected,
> second only to the company lawyers - meaning many
> people could understand only half of what we were
> saying! I considered my job well done when a question
> from my audience was answered by another member of the
> merchant audience - meaning someone "got it."
>
> Glaze knowledge is the same way. In the face of
> novices, if we cling to our JARGON, we will only scare
> off students. The job of a teacher is to present
> information in a way conducive to learning - and to
> me, that demands remembering what it's like NOT to
> know it.
>
>
>
>
>
>
>
>
>
> =====
> Karen Gringhuis
> KG Pottery
> Box 607 Alfred NY 14802
>
> __________________________________
> Do you Yahoo!?
> The New Yahoo! Shopping - with improved product search
> http://shopping.yahoo.com
>
Richard Aerni on wed 8 oct 03
On Tue, 7 Oct 2003 21:47:13 -0700, karen gringhuis
wrote:
>Ivor & anyone else -
>
>>I have not read "the Cushing HANDBOOK" and there may
>not be a copy in Australia in a public library.<
?<
>
>See below.
>
>>From the tenor of your note, you are proposing an
>empiric approach based on direct trials with real
>materials. If so, I would agree.<
I am not going to reprise Karen's excellent post which outlines Val
Cushing's methodology for building glazes; reread her post if you're
interested. I'm here to give a testimonial to his method.
During my brief time of teaching college ceramics, I was appalled by all of
the art educators I was sending out into the world whose only knowledge of
glazes was that they came out of a bottle of came about by following a
brief recipe written on a scrap of paper. At about that time, Robin Hopper
had published a six part series in Ceramics Monthly concerning glaze
development, which I in my ignorance assumed he had worked out, but in
actuality was very similar to Cushing's method described by Karen.
Essentially, Hopper laid out limit formulae for various temperature glazes,
matte and glossy, and grouped glaze materials into categories. By
substituting different similar materials within the categories into the
limit formulae, a student could learn empirically how different materials
affected the finished glaze.
I broke the class down into groups of three, and their assignment, over the
course of the semester, was to experiment a certain number of times, come
up with base glazes that they liked, and then do the experimental color
work after developing the base glazes in the same manner. This project
went on for several months, alongside of their normal work. After a lot of
grumbling, they began to get it, especially after the first few kilnloads
of tests came out. By the end of the semester, they had developed a killer
range of glazes, at various temperatures, with which to glaze the work they
had made. Talk about a bunch of excited students! They had a great
feeling of accomplishment, as well as the feeling that they had somehow
demystified chemistry.
I highly recommend Val Cushing's method.
Best,
Richard Aerni
Bloomfield, NY
Ron Roy on fri 10 oct 03
Certainly having a clear picture of what you want to do before starting is
an advantage but there some serious disadvantages to only using the
empirical approach.
Fir instance - when describing a spar as a flux there is a serious problem
- especially at low and mid fire temperatures. Certainly they do contain
KNaO but also lots of alumina and silica. Adding spar to a cone 6 glaze is
going to decrease the melt.
Expansion is an important factor as well and you get nothing with that
method until you see the crazing or the shivering. Been there done that.
You get no useful information about durability either.
What I am saying here is - those that do not continue on - learning to use
calculation software and the unity molecular formula are working under a
considerable handicap.
The problem is the great amount of information at the beginning - it is
scary - but it is also true that each bit learned is applied to the whole.
Pretty soon the greater part is behind.
I think we potters underestimate what we are capable of learning - if we
could just look back and remember how difficult it was to learn to throw.
The big difference is - throwing looks easy so we are not intimidated.
RR
>At about that time, Robin Hopper
>had published a six part series in Ceramics Monthly concerning glaze
>development, which I in my ignorance assumed he had worked out, but in
>actuality was very similar to Cushing's method described by Karen.
>Essentially, Hopper laid out limit formulae for various temperature glazes,
>matte and glossy, and grouped glaze materials into categories. By
>substituting different similar materials within the categories into the
>limit formulae, a student could learn empirically how different materials
>affected the finished glaze.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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