Vince Pitelka on thu 19 jun 03
Andi -
I have used that glaze since undergrad school in the 60s, and it has always
been a winner at cone 10, in both oxidation and reduction. I have not run
this glaze through a calc program, but it has always been very stable with
little crazing. You will see that it doesn't have much clay in it, but with
the Gerstley in there it presents no application problems. If you have to
eliminate the Gerstley at some point it might be necessary to recalculate
with more clay content.
Honey Luster, Cone 10, Reduction or Oxidation
G-200 or Custer Feldspar - 40.9
Flint - 19.1
Talc - 14.0
Gerstley Borate - 11.5
Dolomite - 7.3
Ball Clay - 7.2
Total - 100
+ Mang. Dioxide 8%
As always, have good ventilation and wear a dust mask while mixing the
glaze, and make sure your kiln is very well ventilated during firing,
especially with the mang. diox. in there.
Good luck -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Office - wpitelka@tntech.edu
615/597-6801 x111, FAX 615/597-6803
http://iweb.tntech.edu/wpitelka/
pdp1@EARTHLINK.NET on sat 21 jun 03
Hey Ron,
She used to be a 'dancer' here...worked the 'Flammingo'
when it opened...retired now, but still really great legs...
Shall I tell her you had inquired?
Phil
lasvegas
----- Original Message -----
From: "Ron Roy"
AM
Subject: Re: looking for honey luster
Vince Pitelka on sat 21 jun 03
> This glaze is probably going to be affected by acid in food to some extent
> - I would guess it will deteroriate in use - the "luster" part is probably
> due to the over saturation of Manganese which cannot stay in solution as
> the glaze cools.
Ron -
I appreciate the recalc using 3234. But regarding the deterioration, in my
experience that has never happened with this glaze. It really has no
"luster" to it at all. The manganese provides a very fine golden honey
color, and there is often some crystal precipitation within the glaze, but
no luster to speak of on the surface. As I said, in use it has always been
a reliable, durable glaze, with no change over time.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Office - wpitelka@tntech.edu
615/597-6801 x111, FAX 615/597-6803
http://iweb.tntech.edu/wpitelka/
Ron Roy on sat 21 jun 03
This glaze is probably going to be affected by acid in food to some extent
- I would guess it will deteroriate in use - the "luster" part is probably
due to the over saturation of Manganese which cannot stay in solution as
the glaze cools.
Here is the same glaze using frit 3134 instead of GB.
G200 - 35.5 (I would expect Custer will give very close results as well)
Talc - 17.0
F3134 - 13.5
Dolomite - 6.0
Ball clay - 7.5 (I used OM#4 - other ball clays may need some adjustment)
EPK - 4.0 (any Kaolin will work)
Silica - 16.5
Total - 100.0
Add 8% Manganese dioxide - dust and firing fumes are toxic.
RR
>Honey Luster, Cone 10, Reduction or Oxidation
>G-200 or Custer Feldspar - 40.9
>Flint - 19.1
>Talc - 14.0
>Gerstley Borate - 11.5
>Dolomite - 7.3
>Ball Clay - 7.2
>Total - 100
>+ Mang. Dioxide 8%
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
John Britt on sun 22 jun 03
Ron,
I am trying to understand your reasoning on the Honey Luster and its
revision.
Of course, I could be incorrect here, but I noticed that from a Seger
perspective, your glaze has less silica (3.1557 vs 3.3977), less alumina
(0.2992 vs 0.2994), more magnesium (0.4850 vs 0.4621) and less boron
(0.1351 vs 0.1573)
(Although from the percent analysis your revision has more alumina,less
silica, more magnesium, and less boron.)
Your lower limit (as listed in the Matrix program), if I have it correct,
for alumina at cone ten is 0.300, silica is 3.500, magnesium is 0.400 and
boron 0.300. (of course Matrix, Insight, Green, Cushing, and Hamer all
have limit variations, some less and some more than yours.)
Without taking too much of your time, how has the revision improved
durability? Is it the increase in magnesium? Decrease in boron?
Just trying to understand.
Thanks for your time and help,
John Britt
Penland Clay
John Britt on mon 23 jun 03
Ron,
Thanks for taking the time to reply.
I understand that the difference is in the Material Definition Table. I do
understand that the information coming out is dependent on the information
going in.
But I am still confused by your statement:
"My comments about the durability are extrapolations of what we found out
about cone 6 glazes. I am simply guessing - not enough alumina and too much
Manganese. Simply a guess that would have to be tested to find out for
sure."
But I thought you said that your glaze was the same alumina and, unless I
misread it, the same manganese?
So that is all on the specific Honey Luster question. Just trying to
understand your reasoning.
And thank you for offering your MDT but I do have your book and will look
it up.
But to a larger question...
I have always wondered about these numbers. I remember reading Val
Cushing's book and was dismayed at the how materials were reduced to vague
generalizations. Take for instance Gerstley borate. I don't have the book
here but if I remember correctly it was something like calcium and boron
and 5 water. (Of course I understand he was doing everything by hand/slide
ruler and also teaching beginnners like me, so some simplification was
good.)
But then getting Insight and seeing how their representation of gerstley
borate was so much more complex and presumably accurate, gave me a bit of
hope for the whole process. So really, gerstley also has potassium,
sodium and silica in fairly significant quantities. But then I got
Hyperglaze and Matrix and noticed how each program representated gerstley
differently.
Then I fed in the same glaze recipe and noticed how each program
calculated the same recipe to a different UMF and percent analysis. I
figured it was not the difference in calculation but rather the difference
in Material Definition Tables.
Then I realized that MDT's, no matter how accurate, are only an average
and that average could and does change daily. (Probably hourly, knowing
the nature of geological deposits, earth movers, conveyer belts, etc.) And
that the material analysis is done by humans who have have a degree of
error.
Then that the scoop I am taking out of the (perhaps contaminated) bin is
not really the exact average. And by the time the air blew over the mixing
bucket taking with it million of atoms. And then that the water I was
using had an effect (especially with calcium) and that the bucket had
residual stuff in it,... etc. etc.
So my belief atom for atom model was a bit diminished. Then I found out
that the exp/cont numbers were not as accurate as I had invisionsed.
Especially since the oxides were not really accounted for, etc.
I quess what I am saying it that the perceived precision of the UMF
creates a false sense of certainity which does not really exist.
Of course, correct me if I am wrong.
I guess I say this because I have yet to see, from personal experience, an
exact duplication of a glaze from UMF. I have tried it many time myself,
used examples from Clayart discussion, etc. Something as simple as
substituting wollastonite for whiting and silica by Tom Buck none the
less!
The revision crazed badly. So the original glaze had some slight crawling
problems from high surface tension but did not craze and the revision had
different problems, ie. crazing. But the molecular analysis was identical.
I guess I see UMF as a model of reality which predicts behaviors in glazes
rather than prescribing them (That may not be the best term.)
What do you think about that?
Just trying to get it all straight,
John Britt
Penland
Ron Roy on mon 23 jun 03
Hi John,
First of all I have rechecked my calculations to be sure and they show the
new glaze with the F 3134 to be an almost perfect match from a mol stand
point - and I would expect the revision to be a dead ringer for the
original.
I did not try to improve the glaze in anyway except to source the boron
from a frit rather than from GB.
The ratio is as close as you can get and not be right on - the expansion is
also close - when I recalc glazes I always refer to them to see just how
close I got.
The silica in the original is 2.92 - it is the same in my revision.
The alumina is 0.28 and 0.28
the MgO is 0.45 and 0.45
The molecular weights are 269.35 and 267.79
I expect the difference is in our respective Material Definition Tables.
I have developed my own right from the start using analysis from the mines.
I notice that most MDT's that come with calculation programs have some
generic analyses and that is probably why you got different results.
If you are using Insight I will gladly send you a copy of mine by the way.
I can also fax you a copy of the analysis I use - two pages from my glaze
course book - you will also find all of them in the back of our book.
John has used those same analysis in his program - there are some minor
variations but we have to understand - these are "typical" and they will
vary somewhat from batch to batch but still - so much better than any
theoretical analysis.
As for the durability comment - limit formulas are not to be applied to
durability - they are - at best - indicators of melt. When John was
researching this aspect he found no references to durability aside from
lead glazes so it is still a work in progress.
My comments about the durability are extrapolations of what we found out
about cone 6 glazes. I am simply guessing - not enough alumina and too much
Manganese. Simply a guess that would have to be tested to find out for
sure.
Vince says it is a stable glaze but I don't think there has been any
objective testing. I am interested in compiling data on durability of cone
10 glazes and I will fire both versions of this glaze to see if it is
stable - and I will report to the list when I do it. I'm still waiting for
kiln shelves but I hear they are on the way.
Let me know if you are interested in exploring why we got such different
results John - it would be educational for all of us to shed some light
here.
RR
>I am trying to understand your reasoning on the Honey Luster and its
>revision.
>
>Of course, I could be incorrect here, but I noticed that from a Seger
>perspective, your glaze has less silica (3.1557 vs 3.3977), less alumina
>(0.2992 vs 0.2994), more magnesium (0.4850 vs 0.4621) and less boron
>(0.1351 vs 0.1573)
>
>(Although from the percent analysis your revision has more alumina,less
>silica, more magnesium, and less boron.)
>
>Your lower limit (as listed in the Matrix program), if I have it correct,
>for alumina at cone ten is 0.300, silica is 3.500, magnesium is 0.400 and
>boron 0.300. (of course Matrix, Insight, Green, Cushing, and Hamer all
>have limit variations, some less and some more than yours.)
>
>Without taking too much of your time, how has the revision improved
>durability? Is it the increase in magnesium? Decrease in boron?
>
>Just trying to understand.
>
>Thanks for your time and help,
>
>John Britt
>Penland Clay
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on mon 23 jun 03
Hi Vince,
Thanks for this - I will test it and let you know how it holds up - John
and I are interested to see if the any of the data on cone 6 glazes holds
up at cone 10. It is important to find out so we can evaluate the glazes we
use as liners.
It is interesting to note that all glazes change somewhat in use - it is
the magnitude of change that is of interest.
I have gotten into the habit of examining the chinaware in restaurants.
Some show wear on the top side or both sides. If only on the top part it is
because of the acid in food - if both sides it's the soap in the dish
washer or both.
The frit is 3134 by the way - just a typo.
RR
>Ron -
>I appreciate the recalc using 3234. But regarding the deterioration, in my
>experience that has never happened with this glaze. It really has no
>"luster" to it at all. The manganese provides a very fine golden honey
>color, and there is often some crystal precipitation within the glaze, but
>no luster to speak of on the surface. As I said, in use it has always been
>a reliable, durable glaze, with no change over time.
>Best wishes -
>- Vince
>
>Vince Pitelka
>Appalachian Center for Craft
>Tennessee Technological University
>1560 Craft Center Drive, Smithville TN 37166
>Home - vpitelka@dtccom.net
>615/597-5376
>Office - wpitelka@tntech.edu
>615/597-6801 x111, FAX 615/597-6803
>http://iweb.tntech.edu/wpitelka/
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
John Hesselberth on wed 25 jun 03
Hi John,
I have to jump in here. Your concerns are valid, but GB is the prime
culprit here. GB is such a variable material that you can't reliably
use it--period. I have 2 analyses for it that are so far off from each
other it is almost unbelievable. Every batch is different and you have
no idea which one the developer of a particular recipe used--or was it
some third batch for which no analysis is available.
So please don't get down on unity calculations because of GB--leave it
out of the picture and unity calculations are extremely useful. That
is exactly why we absolutely refused to use GB in any of the recipes we
developed for our book. And those authors who do use it, or even worse
use the phrase 'GB substitute', are just playing mind games with their
readers--or else they themselves don't realize how variable GB is. No
one knows what GB is and no one who is interested in being able to
reproduce their glazes over time should use it. Source boron from
frits--they may not be perfect, but they are so much better than
anything else that it isn't worth your time or energy to worry about
GB. Most other materials are far more accurately represented by their
analyses than is GB. It is a plague on us potters and thank heavens it
is almost out of our lives!
End of rant.
Regards,
John
On Monday, June 23, 2003, at 09:51 PM, John Britt wrote:
>
> But to a larger question...
>
> I have always wondered about these numbers. I remember reading Val
> Cushing's book and was dismayed at the how materials were reduced to
> vague
> generalizations. Take for instance Gerstley borate. I don't have the
> book
> here but if I remember correctly it was something like calcium and
> boron
> and 5 water. (Of course I understand he was doing everything by
> hand/slide
> ruler and also teaching beginnners like me, so some simplification was
> good.)
>
> But then getting Insight and seeing how their representation of
> gerstley
> borate was so much more complex and presumably accurate, gave me a bit
> of
> hope for the whole process. So really, gerstley also has potassium,
> sodium and silica in fairly significant quantities. But then I got
> Hyperglaze and Matrix and noticed how each program representated
> gerstley
> differently.
>
> Then I fed in the same glaze recipe and noticed how each program
> calculated the same recipe to a different UMF and percent analysis. I
> figured it was not the difference in calculation but rather the
> difference
> in Material Definition Tables.
>
> Then I realized that MDT's, no matter how accurate, are only an average
> and that average could and does change daily. (Probably hourly, knowing
> the nature of geological deposits, earth movers, conveyer belts, etc.)
> And
> that the material analysis is done by humans who have have a degree of
> error.
>
> Then that the scoop I am taking out of the (perhaps contaminated) bin
> is
> not really the exact average. And by the time the air blew over the
> mixing
> bucket taking with it million of atoms. And then that the water I was
> using had an effect (especially with calcium) and that the bucket had
> residual stuff in it,... etc. etc.
>
> So my belief atom for atom model was a bit diminished. Then I found out
> that the exp/cont numbers were not as accurate as I had invisionsed.
> Especially since the oxides were not really accounted for, etc.
>
> I quess what I am saying it that the perceived precision of the UMF
> creates a false sense of certainity which does not really exist.
>
> Of course, correct me if I am wrong.
>
> I guess I say this because I have yet to see, from personal
> experience, an
> exact duplication of a glaze from UMF. I have tried it many time
> myself,
> used examples from Clayart discussion, etc. Something as simple as
> substituting wollastonite for whiting and silica by Tom Buck none the
> less!
>
> The revision crazed badly. So the original glaze had some slight
> crawling
> problems from high surface tension but did not craze and the revision
> had
> different problems, ie. crazing. But the molecular analysis was
> identical.
>
> I guess I see UMF as a model of reality which predicts behaviors in
> glazes
> rather than prescribing them (That may not be the best term.)
>
> What do you think about that?
>
> Just trying to get it all straight,
>
> John Britt
> Penland
>
>
>
http://www.frogpondpottery.com
http://www.masteringglazes.com
John Britt on thu 26 jun 03
John,
Thanks for your answer. But I don't want this to be about gerstely
borate. It is merely the poster child for a variable natural material.
I guess I should have used dolomite or feldspar in the example. Any mined
material would do. (Perhaps materials that are gathered from many mines
and then mixed have a bit more reliability, like grolleg kaolin, custer
feldspar, etc. but they too have variation.) Especially when we are
talking about atoms, molecules, glass and crystals. It is very difficult
to get accuracy. Trends, yes. Valuable insights, yes, but belief in an
atom for atom replacement I think is pushing it a bit. Unless I am
mistaken?
It is about the "view" of total precison that Seger model has taken on.
Yesterday I even forgot to mention the most variable part of the process
and that is the scale accuracy. We can't even get accuracy a the gas pump
which is checked and stamped, certainly every ceramic scale varies as does
every persons ability to balance the tare, keep the residue off the bar,
etc. This accounts for millions of atoms that are misplaced or accidently
added.
I am not getting down on the Seger model, I think it has value and is
about the best we have under the cirsumstances, but I think it is
percieved as something more than it is. Seeing numbers line 3.22 Si, 0.24
KNaO, etc. give the impression that it is the infallable doctrine of the
ceramic church. But I have yet to see someone make the same glaze by
substituting a different material proportedly with atom for atom
accuracy. It is merely an educated guess. I have tried many glaze
alterations by Ron, Tom and others, including myself. They are
substitutes not the same glaze.
I must say I disagree with you about gerstely borate. I think it is a
great matetial, as long as you realize its good and bad points. And that
is the point here. The problem is the same as the Seger model,
perception. If you think of GB as a stable thing then you will have
problems. So it is not the material that is the problem it is the
understanding. You won't get much better reliability from any of the
soluble boron minerals, ulexite, colemanite, or the substitutes that use
them. But knowing this variability allows you to choose. (We have to
learn to love our materials unconditionally. With all there faults and
gifts wrapped in one package.)
Frits are a better in that regard but they too lie about their qualities.
They are not insoluble! They might be in the lab using a perfect ph
solution but in the glaze bucket the ph varies daily.
So I quess it is a fine point about the perception of Seger and the
accuracy of our business but I think it matters. I am just trying to get a
bit of clarity on the subject.
GB Rules Dude.
Thanks,
John
Paul Herman on thu 26 jun 03
Hello to both Johns, and All:
I'm writing about the Gerstley Borate polemic below.
John H states:
GB is such a variable material that you can't reliably
> use it--period.
It is a plague on us potters and thank heavens it
> is almost out of our lives!
Now, that seems a bit heavy handed to me, because I've been using GB for
over 30 years now, with good results. I currently use it (at ^11) in a
clear gloss, a yellow semi matt and in Tom Coleman's Vegas Red glaze. Of
course Tom's recipe calls for 'Colemanite' but I just laughed and subbed
in GB and it works great. Hey Phil, is Vegas Red an old showgirl too,
like Honey Luster?
All three glazes are very dependable, and I haven't noticed the plague
you speak of. I might add that my main interest is not molecular
formulas of glazes. I can appreciate how it might plague a computer
program.
I recently got 200 lbs of the stuff from a friend who does raku. He had
a panic attack when it was disappearing, and bought a ton. So I think I
have a lifetime supply now. If variability is of concern to you, buy
larger quantities, then the changes will be farther apart.
ALL our materials vary to some extent (even frits). It is up to us to
test them and put them to use, as the gurus have tried to flog into us.
When I get closer to using the 'New' 200 lbs, I will test.
Gerstley Borate has been a useful material for me, and will continue to
be.
Good Firings, and Never take for granted.
Paul Herman
Great Basin Pottery
423-725 Scott Road
Doyle, California 96109 US
potter@psln.com
----------
>From: John Hesselberth
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Re: looking for honey luster
>Date: Wed, Jun 25, 2003, 4:06 PM
>
> Hi John,
>
> I have to jump in here. Your concerns are valid, but GB is the prime
> culprit here. GB is such a variable material that you can't reliably
> use it--period. I have 2 analyses for it that are so far off from each
> other it is almost unbelievable. Every batch is different and you have
> no idea which one the developer of a particular recipe used--or was it
> some third batch for which no analysis is available.
>
> So please don't get down on unity calculations because of GB--leave it
> out of the picture and unity calculations are extremely useful. That
> is exactly why we absolutely refused to use GB in any of the recipes we
> developed for our book. And those authors who do use it, or even worse
> use the phrase 'GB substitute', are just playing mind games with their
> readers--or else they themselves don't realize how variable GB is. No
> one knows what GB is and no one who is interested in being able to
> reproduce their glazes over time should use it. Source boron from
> frits--they may not be perfect, but they are so much better than
> anything else that it isn't worth your time or energy to worry about
> GB. Most other materials are far more accurately represented by their
> analyses than is GB. It is a plague on us potters and thank heavens it
> is almost out of our lives!
>
> End of rant.
>
> Regards,
>
> John
>
> On Monday, June 23, 2003, at 09:51 PM, John Britt wrote:
>
>>
>> But to a larger question...
>>
>> I have always wondered about these numbers. I remember reading Val
>> Cushing's book and was dismayed at the how materials were reduced to
>> vague
>> generalizations. Take for instance Gerstley borate. I don't have the
>> book
>> here but if I remember correctly it was something like calcium and
>> boron
>> and 5 water. (Of course I understand he was doing everything by
>> hand/slide
>> ruler and also teaching beginnners like me, so some simplification was
>> good.)
>>
>> But then getting Insight and seeing how their representation of
>> gerstley
>> borate was so much more complex and presumably accurate, gave me a bit
>> of
>> hope for the whole process. So really, gerstley also has potassium,
>> sodium and silica in fairly significant quantities. But then I got
>> Hyperglaze and Matrix and noticed how each program representated
>> gerstley
>> differently.
>>
>> Then I fed in the same glaze recipe and noticed how each program
>> calculated the same recipe to a different UMF and percent analysis. I
>> figured it was not the difference in calculation but rather the
>> difference
>> in Material Definition Tables.
>>
>> Then I realized that MDT's, no matter how accurate, are only an average
>> and that average could and does change daily. (Probably hourly, knowing
>> the nature of geological deposits, earth movers, conveyer belts, etc.)
>> And
>> that the material analysis is done by humans who have have a degree of
>> error.
>>
>> Then that the scoop I am taking out of the (perhaps contaminated) bin
>> is
>> not really the exact average. And by the time the air blew over the
>> mixing
>> bucket taking with it million of atoms. And then that the water I was
>> using had an effect (especially with calcium) and that the bucket had
>> residual stuff in it,... etc. etc.
>>
>> So my belief atom for atom model was a bit diminished. Then I found out
>> that the exp/cont numbers were not as accurate as I had invisionsed.
>> Especially since the oxides were not really accounted for, etc.
>>
>> I quess what I am saying it that the perceived precision of the UMF
>> creates a false sense of certainity which does not really exist.
>>
>> Of course, correct me if I am wrong.
>>
>> I guess I say this because I have yet to see, from personal
>> experience, an
>> exact duplication of a glaze from UMF. I have tried it many time
>> myself,
>> used examples from Clayart discussion, etc. Something as simple as
>> substituting wollastonite for whiting and silica by Tom Buck none the
>> less!
>>
>> The revision crazed badly. So the original glaze had some slight
>> crawling
>> problems from high surface tension but did not craze and the revision
>> had
>> different problems, ie. crazing. But the molecular analysis was
>> identical.
>>
>> I guess I see UMF as a model of reality which predicts behaviors in
>> glazes
>> rather than prescribing them (That may not be the best term.)
>>
>> What do you think about that?
>>
>> Just trying to get it all straight,
>>
>> John Britt
>> Penland
John Britt on fri 27 jun 03
John and Ron,
Actually, now that you mention it gerstley borate proves the point, at
least in my mind.
The fact that the many great minds working on it, from industry to
individuals, have yet to find a satisfactory subsitiute for gerstely
borate calls into question the ability of the UMF model to do the atom for
atom substitution.
Weather it is Cadycal, Boraq 1 ,2 or 3, Gillespie borate, Laguna borate,
or frit subsitiutions, none have proven to be the perfect match.
I am very sure that all the subsitiutes look close or maybe perfect on
paper but the actual properties are far from the same. Some don't
flocculate well, some turn to jelly later, some require other additons at
higher temperatures, some have the same physical properties but the
chemical properties differ and the glazes don't look the same, etc.
This is no criticism of the products or the minds producing them, but
rather throws light on the extreme complexities of natural materials and
the ability of UMF to full account for this.
This is not to take away from Seger or the abilities of the UMF system to
enlighten and explain ceramic glazes, like the cone system, Currie's
system, its unquestioned value in industrial ceramics, etc. But it calls
into question the fundamental belief that by knowing this system and
having calcualtion software will enable you can accuratey exchange natural
materials with atom for atom accuracy.
Wondering what your opinion is on that?
Thanks for your time,
John Brit
Penland Clay
Ron Roy on sat 28 jun 03
Hi John,
My comments (guesses) about the durability of that glaze apply to both
versions - the original and my revision using 3134. They would reveal the
same results if both were tested.
Let me try to answer the question about the variability of materials
analysis and how that affects the calculation of glazes. It's an excellent
question and I have only alluded to the answer over the years.
First of all many of the materials we use are quite consistent. I have been
checking them over the years and have confidence in them. If you ask which
ones - well here is a partial list.
G200
EPK
Talc - Natal
Silica
Frits
Whiting (local supplies need to be checked with analysis from the mine)
Wollastonite (local supplies need to be checked with analysis from the mine)
Dolomite (local supplies need to be checked with analysis from the mine)
Neph Sy (Lake Field 270 M)
You may need to check other materials you are found of using and which you
use in quantity. You will notice the above bears a strong resemblance to
the materials listed in our book. It was not accidental those materials
were chosen. Part of the reason those glazes work so well for so many is
the fact that the materials are very stable and the molecular formulas are
so reliable.
In many cases you can have quite a difference in individual materials and
the glaze will still look the same - the trick is to have many materials in
a glazes so the variations tend to even out. It is the same with clay
bodies - the more clays the more stable the body because you are not too
reliant on the integrity of any one material. If you do want simple stable
glazes - make sure the materials you use have a good track record.
The penchant for simple glazes (only 2 or 3 materials) is the recipe for
failure - sooner or later. I am constantly amazed when I hear this - I can
only surmise this is to make em easy to weigh out. They are the hardest
glazes to deal with when a material goes bad or is discontinued.
I have a lot of faith in calculation - I have been using it in clays and
glazes for over 15 years now and the record of success is truly impressive.
I have no trouble recommending calculation as the most accurate way to
substitute materials, duplicate glazes and bodies, formulate new glazes and
make adjustments for fit and durability.
There is a catch of course - it still requires craftsmanship. The will to
do the best job you can. That means you don't rely on others craftsmanship
unless it proven.
I suggest you go to the Feldspars web site - check out the analysis for
G200 and EPK over the period of a few months - they are posted and updated
frequently.
Gerstley Borate is a special case. Up until a few years ago it was variable
but within limits that we could work with. Then it really took a dip and
should not have been called GB at all - worse still it was no longer
possible to get the analysis from Hammil and Gillespie. That I took as the
writing on the wall. Again - those glaze with only 5 or 10 % GB in them
would still work - one of the main problems turned out to be with those
glaze with a lot of GB - a hint - if you are working with an old recipe use
the old analysis when converting - if you are using an old glaze with the
older GB use that to start with and sub in using the newer analysis of GB.
Better still - cut down the amount of GB or eliminate it and use a suitable
frit.
To answer your observation that you have never seen a duplicate glaze using
calculation to sub in a different material - well I have seen many - and
clay bodies as well. There are many on this list whom I have converted
glazes for - I hope they will speak up. In the meantime I will be happy to
do a few for you. I am confident not only from my experience but in the
faith that my materials analysis are as accurate as they can be.
From the differences in the materials analysis in the programs you were
using I am not surprised the glazes did not look the same. I do think it
will be impossible in some cases. Remember - some of the materials we buy
are not what we think they are - I remember Louis Katz saying the whiting
he got was something else sold as whiting - if you can't get an analysis
for it you have a choice - get one or have the material analyzed - or don't
use it.
Some day we will learn to list the materials we use in our glazes - if we
really do care about sharing them - even better - list the materials and
the real analysis - that will make it all transparent.
I am sure you will have more questions about this - and I welcome them. In
the end learning to use calculation takes some time and we cannot discount
the importance of knowing our materials. Most of us are at the beginning of
applying calculation to glazes and clays.
I must say though - there have recently been a few comments on ClayArt - by
some just starting to use calculation - their comments bring back those
feeling I had at the beginning - of wonder and excitement that there was
finally a window through which I could begin to understand the wonders of
the chemistry of clay and glazes. The difference between being blind and
beginning to see - with the promise of better sight in the future. There
was never any doubt in my mind though - I had to apply as much
craftsmanship as I could - and try as hard as I could to not take anything
for granted.
Hope this does not sound too intimidating - one material at a time gets you
there. Just make sure your analysis are close and know what each oxide does
in the glaze you are working on.
RR
>But I am still confused by your statement:
>
>"My comments about the durability are extrapolations of what we found out
>about cone 6 glazes. I am simply guessing - not enough alumina and too much
>Manganese. Simply a guess that would have to be tested to find out for
>sure."
>
>But I thought you said that your glaze was the same alumina and, unless I
>misread it, the same manganese?
>
>So that is all on the specific Honey Luster question. Just trying to
>understand your reasoning.
>
>And thank you for offering your MDT but I do have your book and will look
>it up.
>
>But to a larger question...
>
>
>
>I have always wondered about these numbers. I remember reading Val
>Cushing's book and was dismayed at the how materials were reduced to vague
>generalizations. Take for instance Gerstley borate. I don't have the book
>here but if I remember correctly it was something like calcium and boron
>and 5 water. (Of course I understand he was doing everything by hand/slide
>ruler and also teaching beginnners like me, so some simplification was
>good.)
>
>But then getting Insight and seeing how their representation of gerstley
>borate was so much more complex and presumably accurate, gave me a bit of
>hope for the whole process. So really, gerstley also has potassium,
>sodium and silica in fairly significant quantities. But then I got
>Hyperglaze and Matrix and noticed how each program representated gerstley
>differently.
>
>Then I fed in the same glaze recipe and noticed how each program
>calculated the same recipe to a different UMF and percent analysis. I
>figured it was not the difference in calculation but rather the difference
>in Material Definition Tables.
>
>Then I realized that MDT's, no matter how accurate, are only an average
>and that average could and does change daily. (Probably hourly, knowing
>the nature of geological deposits, earth movers, conveyer belts, etc.) And
>that the material analysis is done by humans who have have a degree of
>error.
>
>Then that the scoop I am taking out of the (perhaps contaminated) bin is
>not really the exact average. And by the time the air blew over the mixing
>bucket taking with it million of atoms. And then that the water I was
>using had an effect (especially with calcium) and that the bucket had
>residual stuff in it,... etc. etc.
>
>So my belief atom for atom model was a bit diminished. Then I found out
>that the exp/cont numbers were not as accurate as I had invisionsed.
>Especially since the oxides were not really accounted for, etc.
>
>I quess what I am saying it that the perceived precision of the UMF
>creates a false sense of certainity which does not really exist.
>
>Of course, correct me if I am wrong.
>
>I guess I say this because I have yet to see, from personal experience, an
>exact duplication of a glaze from UMF. I have tried it many time myself,
>used examples from Clayart discussion, etc. Something as simple as
>substituting wollastonite for whiting and silica by Tom Buck none the
>less!
>
>The revision crazed badly. So the original glaze had some slight crawling
>problems from high surface tension but did not craze and the revision had
>different problems, ie. crazing. But the molecular analysis was identical.
>
>I guess I see UMF as a model of reality which predicts behaviors in glazes
>rather than prescribing them (That may not be the best term.)
>
>What do you think about that?
>
>Just trying to get it all straight,
>
>John Britt
>Penland
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
John Britt on sat 28 jun 03
Ron,
Ok, my mistake. I thought you were revising Honey Luster to make it more
durable and that is what I did not understand ( That is, if the alumina,
silica and manganese was the same I did not see how the durability would
differ). So all you were doing was to re-sourcing the boron.
Now to the larger question. What I am hearing you say is that, if we all
had accurate MDT and then the materials in our bags were acutally what
were in the MDT, the UMF would be highly accurate and could duplicate
glazes.
So, if there were complete accuracy in mining, analysis, reporting,
weighing, and firing then it would be accurate?
Is that is correct?
Hopefully I am understanding you!
And in your book you try to limit your glazes to materials that are and
have shown over the years to be somewhat stable and reliable. You also try
to have a variety of materials so that variability in one source
won't "greatly" effect the glaze.
What I am hearing here is that the perception that the UMF is an atom for
atom replacement is incorrect. Rather it is a "range' of atoms that we
are replacing and working within that range will make it acceptable. That
is why you say it takes 'craftsmanship". Becasue it is not really a
perfect science where A + B = C, rather it may take some of D to make it
work based on my knowledge and experience? Is that correct?
I guess I should ask you :
How do we deal with materials that vary. It is very hard to get around
them unless you make up all your own recipes from the small handful of
materials you listed. And if we are trying to replicate old recipes or
unusual recipes what do you do?
And what do you mean by craftsmanship and the will to do the best you can?
Then I guess I would ask your opinion on why all the gerstley borate
subsitiutes are close but not quite? (As are the Albany substitutes)Why
Laguna, Gillespie, Boraq 1, 2, 3,and frits etc all have either physical or
chemical characteristics that do not match up?
Is that why you say replacement or replication "would be impossible in
some cases"?
I quess this leads me to the difference between substances (man-made
materials), igneous, sedimantary and metamorphic rocks. How does the UMF
account for that? (Especially, in light of your recent exchange with Ivor
about the purity of oxides in eutetics.) Or does it matter?
Substituting wollasonite for whiting and silica. Someone did a simple
subsitution in a celadon glaze. The revision was similiar but not the same?
Original Celadon
Custer 25
Silica 35
Grolleg 20
Whiting 20
Blk Iron 1
Revision Celadon
Custer 30
Silica 24
Wollasonite 25
Grolleg 21
Black Iron 1
These looked really close on the calculation software. But the glazes were
different. One crazed and the other did not? On a grolleg porcelain.
grolleg 55
custer 25
silica 25
bent 2
Hope that is not to many questions in one post?
Thanks,
John
Ron Roy on mon 30 jun 03
Hello again John,
No I am not saying you have to be dead accurate - there will always be a
difference in the material in your glaze and the analysis for that
material. The question is how much of a difference. Close is fine - there
are very few glazes that are so sensitive that small differences will make
a difference in the look of the glaze. If that is the kind of glaze you
have - so unbalanced that small differences make big changes then you have
an unbalanced glaze - the way it is with some. In that case there is
nothing that will help anyway.
I have worked on many glazes that still looked the same even though I had
to rearrange the fluxes to solve a fit problem.
I am saying - if we have grossly inaccurate material analysis in our data
base we don't have a chance. Getting most of the error out will work just
fine.
If a material naturally varies a lot then have several analysis of that
material and use the ones you think are suitable.
Better still try to find more reliable materials for as many of your glaze
ingredients as possible - maybe even have them analyzed.
I am not even sure that having the exact analysis would make this whole
business easier - there is still the skill factor.
What I am sure of - and I find myself repeating myself now - if your
analysis do not come close to what your are using it cannot work.
I am not sure I can say it is a perfect science - I don't know if all the
materials were represented perfectly - would it be then - how would I know
that? I do know that the people who do the phase diagrams and research have
to do it by experimenting - something that cannot be figured out.
What I do know it that it can be done - because I do it - not every time -
but more often than I have ever been able to do it. And I know that the
care (call it craftsmanship if you like) I take with the analysis I put in
my data base has something to do with it.
The two recipes below are not close at all - and if your analysis are not
at least semi accurate then I would not expect them to be the same. The
expansion is very close so I expect the one that did not craze (#2) will
probably eventually craze. If you don't want it to ever craze it will have
to be lower.
Custer is not as reliable as G200 so that is a factor - were they mixed
with the same bag of Custer?
Wolastonite has some MgO associated with it so that may influence the colour
The alumina was down and the ratio was off - I'm not surprised it did not
look the same.
Here is #2 redone to match as close as possible counting the MgO as an
addition - It's only .04 diff so I don't think you will see it.
Custer 24.0
Silica - 26.0
Wolas - 28.0 (I use the Vansil analysis)
Grolleg - 22.0
Total 100.0
Ratio is very close 8.89/8.91
Expansion is down a bit because of the MgO
Test em out and we can talk about it.
In the end I wish I could give you the concrete answers you are looking for
- I can't do that right now - all I can do is tell you what I have found
out so far - and how to get better results. You are going to have to start
and see if there is a difference.
RR
>Now to the larger question. What I am hearing you say is that, if we all
>had accurate MDT and then the materials in our bags were acutally what
>were in the MDT, the UMF would be highly accurate and could duplicate
>glazes.
>
>So, if there were complete accuracy in mining, analysis, reporting,
>weighing, and firing then it would be accurate?
>
>Is that is correct?
>
>Hopefully I am understanding you!
>
>And in your book you try to limit your glazes to materials that are and
>have shown over the years to be somewhat stable and reliable. You also try
>to have a variety of materials so that variability in one source
>won't "greatly" effect the glaze.
>
>What I am hearing here is that the perception that the UMF is an atom for
>atom replacement is incorrect. Rather it is a "range' of atoms that we
>are replacing and working within that range will make it acceptable. That
>is why you say it takes 'craftsmanship". Becasue it is not really a
>perfect science where A + B = C, rather it may take some of D to make it
>work based on my knowledge and experience? Is that correct?
>
>I guess I should ask you :
>
>How do we deal with materials that vary. It is very hard to get around
>them unless you make up all your own recipes from the small handful of
>materials you listed. And if we are trying to replicate old recipes or
>unusual recipes what do you do?
>
>And what do you mean by craftsmanship and the will to do the best you can?
>
>Then I guess I would ask your opinion on why all the gerstley borate
>subsitiutes are close but not quite? (As are the Albany substitutes)Why
>Laguna, Gillespie, Boraq 1, 2, 3,and frits etc all have either physical or
>chemical characteristics that do not match up?
>
>Is that why you say replacement or replication "would be impossible in
>some cases"?
>
>I quess this leads me to the difference between substances (man-made
>materials), igneous, sedimantary and metamorphic rocks. How does the UMF
>account for that? (Especially, in light of your recent exchange with Ivor
>about the purity of oxides in eutetics.) Or does it matter?
>
>Substituting wollasonite for whiting and silica. Someone did a simple
>subsitution in a celadon glaze. The revision was similiar but not the same?
>Original Celadon
>Custer 25
>Silica 35
>Grolleg 20
>Whiting 20
>Blk Iron 1
>
>Revision Celadon
>Custer 30
>Silica 24
>Wollasonite 25
>Grolleg 21
>Black Iron 1
>
>These looked really close on the calculation software. But the glazes were
>different. One crazed and the other did not? On a grolleg porcelain.
>
>grolleg 55
>custer 25
>silica 25
>bent 2
>
>Hope that is not to many questions in one post?
>
>Thanks,
>
>John
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on mon 30 jun 03
Hello again John,
Good questions again - it really is helping me mine the thought processes
out of my brain.
First we have to understand - many glazes - particularly those that are
well balanced - do not need to be exact to look the same.
Second - some times the results are better than the original in a number of
ways.
Third - if it's not right on it is possible to get closer. This part
depends on individual skill and experience. I am not saying - in any way
that I have arrived at the state where I have nothing more to learn - that
will never happen. I can say that I am better at it than I was a year ago
and way beyond what I could do 10 years ago.
There is so much to read about this and not all of it is even worth reading
because the writer either does not have the experience and/or stopped
learning way before they should have.
This is compounded in that those who do the experiments write in a way that
is mostly not understandable to the great majority of potters. So we have
to learn the language and also try to apply the experience to work.
It is true our scales are crude - which is why we need to use larger batch
sizes when we test - and learn how to balance and test the equipment me use
to minimize the errors.
There is no doubt in my mind that glazes can be duplicated using the Seger
model - and mole % is another way. I have done it so I know it is possible.
I also know I can get better at it. It's a matter of understanding what can
go wrong and finding ways to counteract the problems.
An example: In many glazes you can add two measures (0.5 increments) of say
a clay and the Seger mol # will not change. If you look at the mols of SiO2
and then at the SiO2/Al2O3 ratio you can then see which amount is more
appropriate.
Example 2: If you find - after using Wollastonite to source CaO (instead of
Whiting) and lower the SiO2 to the same level as the original - you will
probably find a little more melting. If you understand about why you would
get more melting you can simply do a short line blend raising the SiO2 and
the Al2O3 - keeping the ratio the same - to overcome that extra melting.
You would soon understand just how much refractory you would have to add to
keep the melt the same.
It's just a matter of learning the tricks and they become part of your skill.
So calculation is - in the end - just a tool - it is still your skill level
that determines the results.
In this case - fixing, inventing and re inventing glazes - there is no
better tool.
If the object is to not think - well then you are stuck with line blending
or simply guessing. It works to a limited degree but in the long term - if
you really want to solve all the problems - including fit and stability -
calculation has the potential.
RR
>Thanks for your answer. But I don't want this to be about gerstely
>borate. It is merely the poster child for a variable natural material.
>
>I guess I should have used dolomite or feldspar in the example. Any mined
>material would do. (Perhaps materials that are gathered from many mines
>and then mixed have a bit more reliability, like grolleg kaolin, custer
>feldspar, etc. but they too have variation.) Especially when we are
>talking about atoms, molecules, glass and crystals. It is very difficult
>to get accuracy. Trends, yes. Valuable insights, yes, but belief in an
>atom for atom replacement I think is pushing it a bit. Unless I am
>mistaken?
>
>It is about the "view" of total precison that Seger model has taken on.
>Yesterday I even forgot to mention the most variable part of the process
>and that is the scale accuracy. We can't even get accuracy a the gas pump
>which is checked and stamped, certainly every ceramic scale varies as does
>every persons ability to balance the tare, keep the residue off the bar,
>etc. This accounts for millions of atoms that are misplaced or accidently
>added.
>
>I am not getting down on the Seger model, I think it has value and is
>about the best we have under the cirsumstances, but I think it is
>percieved as something more than it is. Seeing numbers line 3.22 Si, 0.24
>KNaO, etc. give the impression that it is the infallable doctrine of the
>ceramic church. But I have yet to see someone make the same glaze by
>substituting a different material proportedly with atom for atom
>accuracy. It is merely an educated guess. I have tried many glaze
>alterations by Ron, Tom and others, including myself. They are
>substitutes not the same glaze.
>
>I must say I disagree with you about gerstely borate. I think it is a
>great matetial, as long as you realize its good and bad points. And that
>is the point here. The problem is the same as the Seger model,
>perception. If you think of GB as a stable thing then you will have
>problems. So it is not the material that is the problem it is the
>understanding. You won't get much better reliability from any of the
>soluble boron minerals, ulexite, colemanite, or the substitutes that use
>them. But knowing this variability allows you to choose. (We have to
>learn to love our materials unconditionally. With all there faults and
>gifts wrapped in one package.)
>
>Frits are a better in that regard but they too lie about their qualities.
>They are not insoluble! They might be in the lab using a perfect ph
>solution but in the glaze bucket the ph varies daily.
>
>So I quess it is a fine point about the perception of Seger and the
>accuracy of our business but I think it matters. I am just trying to get a
>bit of clarity on the subject.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on mon 30 jun 03
Hi Paul,
It is not a problem if you are using small amounts - and at cone 10 at
that. But what about the poor souls that are using 50% GB.
What you are advocating here is to use materials that vary a lot - it does
not make sense unless you make sure there are enough materials in a glaze
so the net effect averages out. Even then a majority will sometimes go up
or down together. Not the advice I would give production potters who rely
on keeping things looking the same - or at least getting a full load out
each firing.
Besides - it's almost gone for the great majority of potters and getting
more expensive every time I look - I say good riddance.
RR
>I'm writing about the Gerstley Borate polemic below.
>
>John H states:
>GB is such a variable material that you can't reliably
>> use it--period.
>It is a plague on us potters and thank heavens it
>> is almost out of our lives!
>
>Now, that seems a bit heavy handed to me, because I've been using GB for
>over 30 years now, with good results. I currently use it (at ^11) in a
>clear gloss, a yellow semi matt and in Tom Coleman's Vegas Red glaze. Of
>course Tom's recipe calls for 'Colemanite' but I just laughed and subbed
>in GB and it works great. Hey Phil, is Vegas Red an old showgirl too,
>like Honey Luster?
>
>All three glazes are very dependable, and I haven't noticed the plague
>you speak of. I might add that my main interest is not molecular
>formulas of glazes. I can appreciate how it might plague a computer
>program.
>
>I recently got 200 lbs of the stuff from a friend who does raku. He had
>a panic attack when it was disappearing, and bought a ton. So I think I
>have a lifetime supply now. If variability is of concern to you, buy
>larger quantities, then the changes will be farther apart.
>
>ALL our materials vary to some extent (even frits). It is up to us to
>test them and put them to use, as the gurus have tried to flog into us.
>When I get closer to using the 'New' 200 lbs, I will test.
>
>Gerstley Borate has been a useful material for me, and will continue to
>be.
>
>Good Firings, and Never take for granted.
>
>Paul Herman
>Great Basin Pottery
>423-725 Scott Road
>Doyle, California 96109 US
>potter@psln.com
>
>----------
>>From: John Hesselberth
>>To: CLAYART@LSV.CERAMICS.ORG
>>Subject: Re: looking for honey luster
>>Date: Wed, Jun 25, 2003, 4:06 PM
>>
>
>> Hi John,
>>
>> I have to jump in here. Your concerns are valid, but GB is the prime
>> culprit here. GB is such a variable material that you can't reliably
>> use it--period. I have 2 analyses for it that are so far off from each
>> other it is almost unbelievable. Every batch is different and you have
>> no idea which one the developer of a particular recipe used--or was it
>> some third batch for which no analysis is available.
>>
>> So please don't get down on unity calculations because of GB--leave it
>> out of the picture and unity calculations are extremely useful. That
>> is exactly why we absolutely refused to use GB in any of the recipes we
>> developed for our book. And those authors who do use it, or even worse
>> use the phrase 'GB substitute', are just playing mind games with their
>> readers--or else they themselves don't realize how variable GB is. No
>> one knows what GB is and no one who is interested in being able to
>> reproduce their glazes over time should use it. Source boron from
>> frits--they may not be perfect, but they are so much better than
>> anything else that it isn't worth your time or energy to worry about
>> GB. Most other materials are far more accurately represented by their
>> analyses than is GB. It is a plague on us potters and thank heavens it
>> is almost out of our lives!
>>
>> End of rant.
>>
>> Regards,
>>
>> John
>>
>> On Monday, June 23, 2003, at 09:51 PM, John Britt wrote:
>>
>>>
>>> But to a larger question...
>>>
>>> I have always wondered about these numbers. I remember reading Val
>>> Cushing's book and was dismayed at the how materials were reduced to
>>> vague
>>> generalizations. Take for instance Gerstley borate. I don't have the
>>> book
>>> here but if I remember correctly it was something like calcium and
>>> boron
>>> and 5 water. (Of course I understand he was doing everything by
>>> hand/slide
>>> ruler and also teaching beginnners like me, so some simplification was
>>> good.)
>>>
>>> But then getting Insight and seeing how their representation of
>>> gerstley
>>> borate was so much more complex and presumably accurate, gave me a bit
>>> of
>>> hope for the whole process. So really, gerstley also has potassium,
>>> sodium and silica in fairly significant quantities. But then I got
>>> Hyperglaze and Matrix and noticed how each program representated
>>> gerstley
>>> differently.
>>>
>>> Then I fed in the same glaze recipe and noticed how each program
>>> calculated the same recipe to a different UMF and percent analysis. I
>>> figured it was not the difference in calculation but rather the
>>> difference
>>> in Material Definition Tables.
>>>
>>> Then I realized that MDT's, no matter how accurate, are only an average
>>> and that average could and does change daily. (Probably hourly, knowing
>>> the nature of geological deposits, earth movers, conveyer belts, etc.)
>>> And
>>> that the material analysis is done by humans who have have a degree of
>>> error.
>>>
>>> Then that the scoop I am taking out of the (perhaps contaminated) bin
>>> is
>>> not really the exact average. And by the time the air blew over the
>>> mixing
>>> bucket taking with it million of atoms. And then that the water I was
>>> using had an effect (especially with calcium) and that the bucket had
>>> residual stuff in it,... etc. etc.
>>>
>>> So my belief atom for atom model was a bit diminished. Then I found out
>>> that the exp/cont numbers were not as accurate as I had invisionsed.
>>> Especially since the oxides were not really accounted for, etc.
>>>
>>> I quess what I am saying it that the perceived precision of the UMF
>>> creates a false sense of certainity which does not really exist.
>>>
>>> Of course, correct me if I am wrong.
>>>
>>> I guess I say this because I have yet to see, from personal
>>> experience, an
>>> exact duplication of a glaze from UMF. I have tried it many time
>>> myself,
>>> used examples from Clayart discussion, etc. Something as simple as
>>> substituting wollastonite for whiting and silica by Tom Buck none the
>>> less!
>>>
>>> The revision crazed badly. So the original glaze had some slight
>>> crawling
>>> problems from high surface tension but did not craze and the revision
>>> had
>>> different problems, ie. crazing. But the molecular analysis was
>>> identical.
>>>
>>> I guess I see UMF as a model of reality which predicts behaviors in
>>> glazes
>>> rather than prescribing them (That may not be the best term.)
>>>
>>> What do you think about that?
>>>
>>> Just trying to get it all straight,
>>>
>>> John Britt
>>> Penland
>
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Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on mon 30 jun 03
Hi John,
Yes I think it does make the point - that where you start - or the accuracy
of your start is crucial. In the case of GB which analysis should you start
with. If you start with the material now available - which is quite
different from the older - you have quite a different material. If most of
the glazes we use it in were made with the older, better melters - then the
subs should have been made to emulate that material.
Giiespie Borate is the closest to the run of the mill older varieties -
when I check it next to the current variety it is way off.
What is being sold now should not be called the same as what we used to
get. If we are to do this properly we need to know what material we are
using - in other words the analysis - then it becomes doable.
In the meantime - when dealing with substituting materials, fit problems,
stability etc - the unity molecular formula is the best tool we have. There
is no doubt about that - add to that - getting smart about what you put in
the data base, understanding from reading and observing and using some
creativity to overcome what we know interfers with accuracy - it's all part
of the picture.
In the meantime there are many now working on their glazes and solving
problems - more eveyday I think - it is the beginning of something very
important for potters.
RR
>John and Ron,
>Actually, now that you mention it gerstley borate proves the point, at
>least in my mind.
>
>The fact that the many great minds working on it, from industry to
>individuals, have yet to find a satisfactory subsitiute for gerstely
>borate calls into question the ability of the UMF model to do the atom for
>atom substitution.
>
>Weather it is Cadycal, Boraq 1 ,2 or 3, Gillespie borate, Laguna borate,
>or frit subsitiutions, none have proven to be the perfect match.
>
>I am very sure that all the subsitiutes look close or maybe perfect on
>paper but the actual properties are far from the same. Some don't
>flocculate well, some turn to jelly later, some require other additons at
>higher temperatures, some have the same physical properties but the
>chemical properties differ and the glazes don't look the same, etc.
>
>This is no criticism of the products or the minds producing them, but
>rather throws light on the extreme complexities of natural materials and
>the ability of UMF to full account for this.
>
>This is not to take away from Seger or the abilities of the UMF system to
>enlighten and explain ceramic glazes, like the cone system, Currie's
>system, its unquestioned value in industrial ceramics, etc. But it calls
>into question the fundamental belief that by knowing this system and
>having calcualtion software will enable you can accuratey exchange natural
>materials with atom for atom accuracy.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
John Britt on mon 30 jun 03
Ron,
Thank you so much for trying to explain your thinking! It is really
wonderful. It is so easy to learn about UMF and materials and get the
calculation software and think that is it. But really that is just the
beginning.
Now I see how you are thinking. (The rational on wollastonite and melting)
Also I see how you have evolved over the last 10 years (on clayart) doing
this so often and how one needs that experience to improve.
Yes, it was the same bag of custer.
I will try the recipe and let you know.
Once again thanks for taking the time to educate me,
John
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