Peter Atwood on wed 10 mar 99
Hi All,
I've been following these discussions about the unity formulas and the
value of glaze calculations etc. I have been potting for only a year and
a half and have very limited experience with calculations. I have to
admit that I am a little phobic about jumping into the calc aspect but I
realize that it is inevitable. I figure I'll keep studying books like
Out of the Earth and Hamer for a little while more to get some
understanding of the nature of the materials but I know that eventually
I'll have to have someone show me the math.
Something that has been puzzling me though and you who are most
knowledgable must forgive me, is why everyone has to continually
reinvent the wheel? It seems to me that if you have a set of glaze cores
and you have various fluxes and oxides why can't someone come up with a
system of say Custer Spar glazes for cone ten. You don't need fifty or a
thousand different combinations to use custer and a few other
ingredients to make a matt or a shiny glaze. You don't need an infinite
number of adjustments to make it fit a claybody if most claybodies have
say 9-12 percent shrinkage. There must be some sort of basic set of
glazes to which colorants could be added to make workable glazes.
I know what you all will say. You're probably going to make the point
that there are so many ingredients and combinations possible that it is
indeed infinite. And no doubt there is often a great effect on a glaze
from the colorant oxides as David Hewitt points out with his
crazing/noncrazing experiments so starting with a base glaze and adding
colorants won't necessarily work.
I just find it overwhelming and a bit bewildering to enter this ceramic
world and find it so utterly chaotic and complicated. It's obvious that
I'm not the only one.
--Peter ATwood
Get Your Private, Free Email at http://www.hotmail.com
Bill Williams on thu 11 mar 99
AMEN AND EVERYONE SAID, "AMEN". Connie
-----Original Message-----
From: Peter Atwood
To: CLAYART@LSV.UKY.EDU
Date: Wednesday, March 10, 1999 10:09 AM
Subject: glaze formulas
----------------------------Original message----------------------------
Hi All,
I've been following these discussions about the unity formulas and the
value of glaze calculations etc. I have been potting for only a year and
a half and have very limited experience with calculations. I have to
admit that I am a little phobic about jumping into the calc aspect but I
realize that it is inevitable. I figure I'll keep studying books like
Out of the Earth and Hamer for a little while more to get some
understanding of the nature of the materials but I know that eventually
I'll have to have someone show me the math.
Something that has been puzzling me though and you who are most
knowledgable must forgive me, is why everyone has to continually
reinvent the wheel? It seems to me that if you have a set of glaze cores
and you have various fluxes and oxides why can't someone come up with a
system of say Custer Spar glazes for cone ten. You don't need fifty or a
thousand different combinations to use custer and a few other
ingredients to make a matt or a shiny glaze. You don't need an infinite
number of adjustments to make it fit a claybody if most claybodies have
say 9-12 percent shrinkage. There must be some sort of basic set of
glazes to which colorants could be added to make workable glazes.
I know what you all will say. You're probably going to make the point
that there are so many ingredients and combinations possible that it is
indeed infinite. And no doubt there is often a great effect on a glaze
from the colorant oxides as David Hewitt points out with his
crazing/noncrazing experiments so starting with a base glaze and adding
colorants won't necessarily work.
I just find it overwhelming and a bit bewildering to enter this ceramic
world and find it so utterly chaotic and complicated. It's obvious that
I'm not the only one.
--Peter ATwood
Get Your Private, Free Email at http://www.hotmail.com
Craig Martell on fri 12 mar 99
Peter Atwood said:
>Something that has been puzzling me though and you who are most
>knowledgable must forgive me, is why everyone has to continually
>reinvent the wheel? It seems to me that if you have a set of glaze cores
>and you have various fluxes and oxides why can't someone come up with >a
system of say Custer Spar glazes for cone ten. You don't need fifty or a
>thousand different combinations to use custer and a few other
>ingredients to make a matt or a shiny glaze. You don't need an infinite
>number of adjustments to make it fit a claybody if most claybodies have
>say 9-12 percent shrinkage.
Hey Peter:
There are guidelines for different types of feldspathic glazes and they have
to do with what you want in terms of surface, color response, crystalline
matts etc. These glaze types are expressed mostly in the Seger formula as
to how much of a given oxide one needs for a certain response. But, it's
not as simple as having a standard compilation of formulas or receipes that
one can draw from and expect to get a predictable result. You have to
remember too that shrinkage is not the same as thermal expansion and it is
the expansion factor that will determine glaze fit. Glazes have an
expansion value and so do clay bodies. They need to be within certain
parameters for a good "fit" situation to occur. This isn't a simple matter
to deal with but it can be done when one has a certain level of experience
with materials. It is not an absolute necessity to know glaze calc to
attain good fit, but it is certainly helpful.
Things would be approaching a state of "generic" when myriads of potters
were relying on standard formulas for many glaze types. This is already
true to a certain degree but it could be a lot more evident. I find it
pretty liberating to be able to make my glazes and do adjustments and
variants of things. It is the infinite possibilities that keep me going,
and the search for what hasn't happened yet. This is true in all the
aspects of claywork in regard to how I approach things. I don't expect
everyone to feel this way and it's just my "approach", not the "one true
way". We are all different.
>I just find it overwhelming and a bit bewildering to enter this ceramic
>world and find it so utterly chaotic and complicated. It's obvious that
>I'm not the only one.
While all this stuff can be quite bewildering, I don't think that it is
necessarily chaotic. We have a ton of resources at our disposal which aid
in the understanding of all sorts of technical issues in ceramics. I don't
think anyone has ever promised that this would all be "easy". It is a
challenging craft and enjoying the journey and the amount of learning can
make things a lot more pleasant and rewarding.
I think that your use of materials resource books proir to doing the glaze
calc thing is good. It's also fine to do both at the same time but if I had
to do one before the other, I would, and did, do it just as you are. Glaze
calc is not infinitely difficult. It just requires some understanding of
glaze basics and a good amount of method and organization. The computer
programs save such an incredible amount of time. I used to do calc with a
calculator and paper and pencil. This is time consuming. There is one guy
on the list, who I won't mention by name, that started doing calc with a
slide rule, if you want to talk about real consumtion of time.
regards, Craig Martell in Oregon
Ron Roy on sat 13 mar 99
Hi Peter,
I think your point about having a few base glazes is a good one - the
problem we have now is - Most don't know enough about what makes particular
glazes work. The traditional way (BCC - before computer calculation) was
and mostly still is - find a glaze that sounds like what you want and try
it. Part of the skill in selling or otherwise disseminating text book
glazes is in naming them.
The problems with this approach are many - different materials, different
firing, different clay bodies, no ratio number - in other words no
molecular formula without which there is no meaningful base for comparison.
One of the huge disadvantages - no info on expansion/contraction - you can
spot the crazing glazes most times - especially if you test by freezing and
boiling - but you often don't find the opposite problem till ware starts
coming back cracked.
By the way - expansion is calculated from the percent oxides. I use this
feature a lot in solving fit problems. I find it very reliable in the great
majority of glazes I need to deal with. It is even possible to calculate
expansion from materials. You must take into account LOI and you need the
expansion of the material as well.
By the way - your statement "most clay bodies have a shrinkage of 9 to 12
percent" this has nothing to do with glaze fit. This shrinkage is from
drying and firing. Once the clay has gone through it - it is not
reversible. It is only when the glaze solidifies (sets or freezes) do the
different cooling contractions begin to generate stress. Most of our
glazes solidify between 700C to 500C - much lower than we usually assume.
Expansion/contraction is the expansion of a material as it is heated -
contraction is what happens as a material is cooled (there are exceptions
but our materials are almost always straight forward) These movements are
directly reversible. If it starts out as 1.0 at 50C and grows to 2.0 at
200C it will return to 1.0 when it gets back to 50C. These changes are very
small but - glaze (glass) being considerably more rigid than rubber for
instance - cannot take much tension - it can take considerably more
compression however.
Our problems arise because clays expand on heating and contract on cooling
in different amounts than our glazes. We use these differences to make our
materials compatible so it should not be viewed as bad news - but without
calculation the problem is infinitely more difficult to deal with.
If you wana talk more about this - wait till NCECA is over - I'll be back
March 23.
RR
>----------------------------Original message----------------------------
>Something that has been puzzling me though and you who are most
>knowledgable must forgive me, is why everyone has to continually
>reinvent the wheel? It seems to me that if you have a set of glaze cores
>and you have various fluxes and oxides why can't someone come up with a
>system of say Custer Spar glazes for cone ten. You don't need fifty or a
>thousand different combinations to use custer and a few other
>ingredients to make a matt or a shiny glaze. You don't need an infinite
>number of adjustments to make it fit a claybody if most claybodies have
>say 9-12 percent shrinkage. There must be some sort of basic set of
>glazes to which colorants could be added to make workable glazes.
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
Edouard Bastarache on sat 13 mar 99
------------------
Hello Craig,
i started making glaze calculation without
a slide rule and without a hand calculator,
but i liked it.
That was quite many years ago.
Later,
Edouard Bastarache
edouardb=40sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/=7Eedouardb/
-----Message d'origine-----
De : Craig Martell =3Cashglaze=40teleport.com=3E
=C0 : CLAYART=40LSV.UKY.EDU =3CCLAYART=40LSV.UKY.EDU=3E
Date : 12 mars, 1999 14:29
Objet : Re: glaze formulas
=3E----------------------------Original message----------------------------
=3EPeter Atwood said:
=3E=3ESomething that has been puzzling me though and you who are most
=3E=3Eknowledgable must forgive me, is why everyone has to continually
=3E=3Ereinvent the wheel? It seems to me that if you have a set of glaze =
cores
=3E=3Eand you have various fluxes and oxides why can't someone come up with =
=3Ea
=3Esystem of say Custer Spar glazes for cone ten. You don't need fifty or a
=3E=3Ethousand different combinations to use custer and a few other
=3E=3Eingredients to make a matt or a shiny glaze. You don't need an =
infinite
=3E=3Enumber of adjustments to make it fit a claybody if most claybodies =
have
=3E=3Esay 9-12 percent shrinkage.
=3E
=3EHey Peter:
=3E
=3EThere are guidelines for different types of feldspathic glazes and they
have
=3Eto do with what you want in terms of surface, color response, crystalline
=3Ematts etc. These glaze types are expressed mostly in the Seger formula =
as
=3Eto how much of a given oxide one needs for a certain response. But, it's
=3Enot as simple as having a standard compilation of formulas or receipes =
that
=3Eone can draw from and expect to get a predictable result. You have to
=3Eremember too that shrinkage is not the same as thermal expansion and it =
is
=3Ethe expansion factor that will determine glaze fit. Glazes have an
=3Eexpansion value and so do clay bodies. They need to be within certain
=3Eparameters for a good =22fit=22 situation to occur. This isn't a simple =
matter
=3Eto deal with but it can be done when one has a certain level of =
experience
=3Ewith materials. It is not an absolute necessity to know glaze calc to
=3Eattain good fit, but it is certainly helpful.
=3E
=3EThings would be approaching a state of =22generic=22 when myriads of =
potters
=3Ewere relying on standard formulas for many glaze types. This is already
=3Etrue to a certain degree but it could be a lot more evident. I find it
=3Epretty liberating to be able to make my glazes and do adjustments and
=3Evariants of things. It is the infinite possibilities that keep me going,
=3Eand the search for what hasn't happened yet. This is true in all the
=3Easpects of claywork in regard to how I approach things. I don't expect
=3Eeveryone to feel this way and it's just my =22approach=22, not the =22one=
true
=3Eway=22. We are all different.
=3E
=3E=3EI just find it overwhelming and a bit bewildering to enter this =
ceramic
=3E=3Eworld and find it so utterly chaotic and complicated. It's obvious =
that
=3E=3EI'm not the only one.
=3E
=3EWhile all this stuff can be quite bewildering, I don't think that it is
=3Enecessarily chaotic. We have a ton of resources at our disposal which =
aid
=3Ein the understanding of all sorts of technical issues in ceramics. I =
don't
=3Ethink anyone has ever promised that this would all be =22easy=22. It is =
a
=3Echallenging craft and enjoying the journey and the amount of learning can
=3Emake things a lot more pleasant and rewarding.
=3E
=3EI think that your use of materials resource books proir to doing the =
glaze
=3Ecalc thing is good. It's also fine to do both at the same time but if I
had
=3Eto do one before the other, I would, and did, do it just as you are. =
Glaze
=3Ecalc is not infinitely difficult. It just requires some understanding of
=3Eglaze basics and a good amount of method and organization. The computer
=3Eprograms save such an incredible amount of time. I used to do calc with =
a
=3Ecalculator and paper and pencil. This is time consuming. There is one =
guy
=3Eon the list, who I won't mention by name, that started doing calc with a
=3Eslide rule, if you want to talk about real consumtion of time.
=3E
=3Eregards, Craig Martell in Oregon
Beth Ward on mon 15 mar 99
<< I just find it overwhelming and a bit bewildering to enter this ceramic
world and find it so utterly chaotic and complicated. It's obvious that
I'm not the only one.
--Peter ATwood >>
Peter:
I really believe that you just summed up why so many of us love pottery.
(Utterly chaotic and complicated.) What could be more fun??
Nothing is worse than doing the same-old-same-old your whole life.
Pottery is never the same!
Between choosing clay bodies, firing techniques, colors, glazes, terra
sigilattas, type of kiln, size of kiln etc. There are unending things to make
you crazy!! (just like having kids only cheaper!)
I personally think most potters are very smart and deserve respect.
Beth
Muddfolks@AOL.com
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