Craig Martell on sat 31 mar 07
Hello Folks:
I've been reading the debate about using or not using the Seger Formula for
clays. It would seem that if one follows the line of reasoning that the
Seger formula is only relevant to glass you shouldn't use it for
crystalline matt glazes either. My feeling is, yes, you can use the Seger
formula to look at the oxide balance in claybodies and yes, it is useful
and relevant.
I use the Seger to look at clays. Mainly vapor glazing bodies that require
a specific silica/alumina ratio to enhance salt or soda vapor glazing. I
use R2O3 unity which places the alumina value at 1.0 and this gives a much
better expression of the molecular structure of the clays than using the
1.0 value for the fluxes.
Also, with regard to aging and mixing, I think that aging is the least
important factor in good, plastic, throwing bodies. The makeup of the
clay/flux/quartz and how the body is mixed are paramount to a good body. I
mixed a new porcelain a couple of weeks ago with two ECC kaolins, J-2 Ball
Clay, G-200 spar, and quartz. It threw very well after sitting for three
days. I mixed about 300 lbs and threw several different forms to see how
the clay would do.
regards, Craig Martell Hopewell, Oregon
Matthew Katz on sun 1 apr 07
Hi Craig,
Just for clarification, are you postulating that the Seger (I call it UMF)
is irrelevant for Matte Glazes, Or are you just trying to draw the analogy
to Bodies and the UMF?
First, I should say that I will be referring to Cone 6 and above. Cone 04
Bodies are another beast entirely. Second, I'm sorry if this some of this is
old hat for you, but I assume others are reading along, so I am going to
give a little background.
You are correct that by normalizing to the Alumina you are getting a more
complete picture of the glasses being developed in the body. The problem
falls in that the initial glass formation is the not the factor to be
concerned with. In a High temperature body the more important factors are a)
The Mullite that forms in the body. b) The free quartz to glass
relationship.
In the firing process the glass forms and proceeds to consume as much free
quartz as it can (The mullite is immune to the solubility of glass and
provides the internal skeletal structure). So the glass uses the energy of
the kiln to aid in the dissolution of the quartz in the system making a
silica rich glass. As soon as the glass has consumed all of the free quartz,
because it has nowhere else to focus it's energy the viscosity of the glass
begins to drop rapidly This causes Pyro-Plastic Deformation (Slumping). So
we need a system that is able to predict how much quartz the glass will
consume, and leave just a little but at the end of the firing, to keep the
viscosity from dropping and the work from slumping
So, the problem with applying the UMF to clays is that it will only tell you
how much glass will form initially, but it makes no account for the glass
that forms as quartz is consumed. And we cannot assume that all the Quartz
presented in the UMF is free quartz because most of it is associated with
the clay. So in the end the UMF glass number is irrelevant because it does
nothing to tell you how much glass is actually formed in the body, and the
body has just as much possibility of slumping if you had not used the UMF on
it.
We work with a system that Bill (Carty) developed, where we have tracked the
behaviors of quartz dissolution in porcelain glasses and we applied that to
a spreadsheet, that is then able to predict Mullite, Glass, and Free Quartz
relationships based on Firing temperature, with relative certainty. It is
just as elegant for clays, as the UMF is for Glazes. Hopefully someday down
the road we will be able to publish a version that is good enough for public
consumption, but right now the version we have is pretty Gnarly, and takes a
lot of training to use effectively.
So I hope that explains why some of us are uncomfortable with using the UMF
to predict the performance of Bodies.
It is great for glazes though... The Bees Knees. If I do say so myself.
Glad to hear that you are a dedicated mixer! It will serve you well.
Best,
Matt
On 3/31/07, Craig Martell wrote:
>
> Hello Folks:
>
> I've been reading the debate about using or not using the Seger Formula
> for
> clays. It would seem that if one follows the line of reasoning that the
> Seger formula is only relevant to glass you shouldn't use it for
> crystalline matt glazes either. My feeling is, yes, you can use the Seger
> formula to look at the oxide balance in claybodies and yes, it is useful
> and relevant.
>
> I use the Seger to look at clays. Mainly vapor glazing bodies that
> require
> a specific silica/alumina ratio to enhance salt or soda vapor glazing. I
> use R2O3 unity which places the alumina value at 1.0 and this gives a much
> better expression of the molecular structure of the clays than using the
> 1.0 value for the fluxes.
>
> Also, with regard to aging and mixing, I think that aging is the least
> important factor in good, plastic, throwing bodies. The makeup of the
> clay/flux/quartz and how the body is mixed are paramount to a good
> body. I
> mixed a new porcelain a couple of weeks ago with two ECC kaolins, J-2 Ball
> Clay, G-200 spar, and quartz. It threw very well after sitting for three
> days. I mixed about 300 lbs and threw several different forms to see how
> the clay would do.
>
> regards, Craig Martell Hopewell, Oregon
>
>
> ______________________________________________________________________________
> 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.
>
--
Matthew Katz
Alfred, NY
Craig Martell on sun 1 apr 07
Matt was asking:
>Just for clarification, are you postulating that the Seger (I call it UMF)
>is irrelevant for Matte Glazes,
Hello Matt:
No, I wasn't thinking that calculation was irrelevant for Mattes. The idea
that the Seger method was not applicable to Claybodies because of the
crystalline structure, and it only applies to glass, made me think about
the fact that the mattes may be more crystalline than glass so where do you
draw the line about using the Seger Formula. I know, very nit picky but I
couldn't resist.
Thanks for the reply and all the great info you've posted in the last week
or so.
regards, Craig Martell Hopewell, Oregon
>Or are you just trying to draw the analogy
>to Bodies and the UMF?
>First, I should say that I will be referring to Cone 6 and above. Cone 04
>Bodies are another beast entirely. Second, I'm sorry if this some of this is
>old hat for you, but I assume others are reading along, so I am going to
>give a little background.
>You are correct that by normalizing to the Alumina you are getting a more
>complete picture of the glasses being developed in the body. The problem
>falls in that the initial glass formation is the not the factor to be
>concerned with. In a High temperature body the more important factors are a)
>The Mullite that forms in the body. b) The free quartz to glass
>relationship.
>In the firing process the glass forms and proceeds to consume as much free
>quartz as it can (The mullite is immune to the solubility of glass and
>provides the internal skeletal structure). So the glass uses the energy of
>the kiln to aid in the dissolution of the quartz in the system making a
>silica rich glass. As soon as the glass has consumed all of the free quartz,
>because it has nowhere else to focus it's energy the viscosity of the glass
>begins to drop rapidly This causes Pyro-Plastic Deformation (Slumping). So
>we need a system that is able to predict how much quartz the glass will
>consume, and leave just a little but at the end of the firing, to keep the
>viscosity from dropping and the work from slumping
>So, the problem with applying the UMF to clays is that it will only tell you
>how much glass will form initially, but it makes no account for the glass
>that forms as quartz is consumed. And we cannot assume that all the Quartz
>presented in the UMF is free quartz because most of it is associated with
>the clay. So in the end the UMF glass number is irrelevant because it does
>nothing to tell you how much glass is actually formed in the body, and the
>body has just as much possibility of slumping if you had not used the UMF on
>it.
>We work with a system that Bill (Carty) developed, where we have tracked the
>behaviors of quartz dissolution in porcelain glasses and we applied that to
>a spreadsheet, that is then able to predict Mullite, Glass, and Free Quartz
>relationships based on Firing temperature, with relative certainty. It is
>just as elegant for clays, as the UMF is for Glazes. Hopefully someday down
>the road we will be able to publish a version that is good enough for public
>consumption, but right now the version we have is pretty Gnarly, and takes a
>lot of training to use effectively.
>So I hope that explains why some of us are uncomfortable with using the UMF
>to predict the performance of Bodies.
>It is great for glazes though... The Bees Knees. If I do say so myself.
>Glad to hear that you are a dedicated mixer! It will serve you well.
>Best,
>Matt
>
>
>On 3/31/07, Craig Martell wrote:
>>
>>Hello Folks:
>>
>>I've been reading the debate about using or not using the Seger Formula
>>for
>>clays. It would seem that if one follows the line of reasoning that the
>>Seger formula is only relevant to glass you shouldn't use it for
>>crystalline matt glazes either. My feeling is, yes, you can use the Seger
>>formula to look at the oxide balance in claybodies and yes, it is useful
>>and relevant.
>>
>>I use the Seger to look at clays. Mainly vapor glazing bodies that
>>require
>>a specific silica/alumina ratio to enhance salt or soda vapor glazing. I
>>use R2O3 unity which places the alumina value at 1.0 and this gives a much
>>better expression of the molecular structure of the clays than using the
>>1.0 value for the fluxes.
>>
>>Also, with regard to aging and mixing, I think that aging is the least
>>important factor in good, plastic, throwing bodies. The makeup of the
>>clay/flux/quartz and how the body is mixed are paramount to a good
>>body. I
>>mixed a new porcelain a couple of weeks ago with two ECC kaolins, J-2 Ball
>>Clay, G-200 spar, and quartz. It threw very well after sitting for three
>>days. I mixed about 300 lbs and threw several different forms to see how
>>the clay would do.
>>
>>regards, Craig Martell Hopewell, Oregon
>>
>>
>>__________________________________________________________________________
>>____
>>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.
>
>
>
>--
>Matthew Katz
>Alfred, NY
>
>______________________________________________________________________________
>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.
Ivor and Olive Lewis on mon 2 apr 07
Dear Matthew Katz,=20
Does the system you describe allow you to predict the Coefficient of =
Linear Thermal Expansion of a high temperature body?
If it does then it would be a very useful tool in preventing crazing and =
shivering.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Matthew Katz on mon 2 apr 07
Hi Ivor,
Yes it can, But we find that is is much easier to use the UMF (Seger)
formula to predict those behaviors in the glazes themselves. Reason being
that it is much easier to make adjustments to (or discard if necessary) a
glaze after the initial mixing than a clay.
On 4/2/07, Ivor and Olive Lewis wrote:
>
> Dear Matthew Katz,
>
> Does the system you describe allow you to predict the Coefficient of
> Linear Thermal Expansion of a high temperature body?
>
> If it does then it would be a very useful tool in preventing crazing and
> shivering.
>
> Best regards,
>
> Ivor Lewis.
> Redhill,
> South Australia.
>
>
> ______________________________________________________________________________
> 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.
>
--
Matthew Katz
Alfred, NY
Matthew Katz on mon 2 apr 07
Ahh,
I thought that was where you were going but I just wanted to make sure.
The cool thing about the UMF and Matte glazes is that in a properly
formulated Matte is that all of the Material melts completely, so to say
that if you pulled the glaze out of the kiln at peak temperature it would be
perfectly glossy. The cristalization happen on the cooling where excess RO
(calcium. MgO, Etc) in Glasses with a Si:Al ratio under 5:1, combine with
excess Alumina and a little bit of free Silica to percipitate Anorthite (or
the relevant mineral based on the RO in use, Corderite for MgO. etc.).
So the major difference is that bodies never totally melt. So by using the
UMF you are trying to predict the behavior if crystalline materials that are
not associate with the formation of glass (ie. Mullite growth and Quartz
dissolution).
And as far as using it to substitute in bodies for green performance. the
UMF/Chemical analysis is virtually irrelevant, because the more important
factors are SSA, Morphology, and GPD of the respective materials.
Best,
Matt
On 4/1/07, Craig Martell wrote:
>
> Matt was asking:
> >Just for clarification, are you postulating that the Seger (I call it
> UMF)
> >is irrelevant for Matte Glazes,
>
> Hello Matt:
>
> No, I wasn't thinking that calculation was irrelevant for Mattes. The
> idea
> that the Seger method was not applicable to Claybodies because of the
> crystalline structure, and it only applies to glass, made me think about
> the fact that the mattes may be more crystalline than glass so where do
> you
> draw the line about using the Seger Formula. I know, very nit picky but I
> couldn't resist.
>
> Thanks for the reply and all the great info you've posted in the last week
> or so.
>
> regards, Craig Martell Hopewell, Oregon
>
>
>
>
>
>
>
>
>
>
> >Or are you just trying to draw the analogy
> >to Bodies and the UMF?
> >First, I should say that I will be referring to Cone 6 and above. Cone 04
> >Bodies are another beast entirely. Second, I'm sorry if this some of this
> is
> >old hat for you, but I assume others are reading along, so I am going to
> >give a little background.
> >You are correct that by normalizing to the Alumina you are getting a more
> >complete picture of the glasses being developed in the body. The problem
> >falls in that the initial glass formation is the not the factor to be
> >concerned with. In a High temperature body the more important factors are
> a)
> >The Mullite that forms in the body. b) The free quartz to glass
> >relationship.
> >In the firing process the glass forms and proceeds to consume as much
> free
> >quartz as it can (The mullite is immune to the solubility of glass and
> >provides the internal skeletal structure). So the glass uses the energy
> of
> >the kiln to aid in the dissolution of the quartz in the system making a
> >silica rich glass. As soon as the glass has consumed all of the free
> quartz,
> >because it has nowhere else to focus it's energy the viscosity of the
> glass
> >begins to drop rapidly This causes Pyro-Plastic Deformation (Slumping).
> So
> >we need a system that is able to predict how much quartz the glass will
> >consume, and leave just a little but at the end of the firing, to keep
> the
> >viscosity from dropping and the work from slumping
> >So, the problem with applying the UMF to clays is that it will only tell
> you
> >how much glass will form initially, but it makes no account for the glass
> >that forms as quartz is consumed. And we cannot assume that all the
> Quartz
> >presented in the UMF is free quartz because most of it is associated with
> >the clay. So in the end the UMF glass number is irrelevant because it
> does
> >nothing to tell you how much glass is actually formed in the body, and
> the
> >body has just as much possibility of slumping if you had not used the UMF
> on
> >it.
> >We work with a system that Bill (Carty) developed, where we have tracked
> the
> >behaviors of quartz dissolution in porcelain glasses and we applied that
> to
> >a spreadsheet, that is then able to predict Mullite, Glass, and Free
> Quartz
> >relationships based on Firing temperature, with relative certainty. It is
> >just as elegant for clays, as the UMF is for Glazes. Hopefully someday
> down
> >the road we will be able to publish a version that is good enough for
> public
> >consumption, but right now the version we have is pretty Gnarly, and
> takes a
> >lot of training to use effectively.
> >So I hope that explains why some of us are uncomfortable with using the
> UMF
> >to predict the performance of Bodies.
> >It is great for glazes though... The Bees Knees. If I do say so myself.
> >Glad to hear that you are a dedicated mixer! It will serve you well.
> >Best,
> >Matt
> >
> >
> >On 3/31/07, Craig Martell wrote:
> >>
> >>Hello Folks:
> >>
> >>I've been reading the debate about using or not using the Seger Formula
> >>for
> >>clays. It would seem that if one follows the line of reasoning that the
> >>Seger formula is only relevant to glass you shouldn't use it for
> >>crystalline matt glazes either. My feeling is, yes, you can use the
> Seger
> >>formula to look at the oxide balance in claybodies and yes, it is useful
> >>and relevant.
> >>
> >>I use the Seger to look at clays. Mainly vapor glazing bodies that
> >>require
> >>a specific silica/alumina ratio to enhance salt or soda vapor
> glazing. I
> >>use R2O3 unity which places the alumina value at 1.0 and this gives a
> much
> >>better expression of the molecular structure of the clays than using the
> >>1.0 value for the fluxes.
> >>
> >>Also, with regard to aging and mixing, I think that aging is the least
> >>important factor in good, plastic, throwing bodies. The makeup of the
> >>clay/flux/quartz and how the body is mixed are paramount to a good
> >>body. I
> >>mixed a new porcelain a couple of weeks ago with two ECC kaolins, J-2
> Ball
> >>Clay, G-200 spar, and quartz. It threw very well after sitting for
> three
> >>days. I mixed about 300 lbs and threw several different forms to see
> how
> >>the clay would do.
> >>
> >>regards, Craig Martell Hopewell, Oregon
> >>
> >>
>
> >>__________________________________________________________________________
> >>____
> >>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.
> >
> >
> >
> >--
> >Matthew Katz
> >Alfred, NY
> >
>
> >______________________________________________________________________________
> >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.
>
>
> ______________________________________________________________________________
> 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.
>
--
Matthew Katz
Alfred, NY
Craig Martell on mon 2 apr 07
Matt clued me in by saying:
>The cool thing about the UMF and Matte glazes is that in a properly
>formulated Matte is that all of the Material melts completely, so to say
>that if you pulled the glaze out of the kiln at peak temperature it would be
>perfectly glossy.
Hello Matt:
Thanks for another response. I know this stuff but what I didn't know was
the critical distinction regarding glazes that devitrify. Now I do.
What fries my head about the crystalline mattes, especially the MgO mattes
is the difference in coefficient or expansion relating to the cooled state
of the glaze. MgO has a lower COE than many of the fluxing oxides we use
but will not eliminate crazing in the crystalline state. Well, sometimes
it won't. I have one matte that I use and the MgO is about 0.3 molecular
equivalents, if I can use that terminology. When I cool it fast and keep
the crystals down it will fit my porcelains. When cooled slowly and there
is more crystalization, it will craze probably due to the fact that
crystalline stuff has a higher COE than bright fused glazes.
To further explain my use of the Seger for Clays, I just use it to look at
the fired form of the claybody when the LOI is a done deal etc. I can also
look at the Si/Al ratio and compare it to other bodies without wearing out
my calculator. I've never used it to actually formulate a body. I do that
the old slow way by testing everything and doing the post firing
examination of absorbtion, shrinkage, exams of bars made to test
pyroplastic deformation etc ad nauseum.
I've known people to use the Seger to substitute materials when something
has gone south or is no longer on the market. A friend was helping another
friend find a sub for C-1 clay in a large production tile company and they
used the Matrix glaze calc program and from what I understand, it helped
them a good deal. Anyway................................
regards, Craig Martell Hopewell, Oregon
Dan Semler on mon 2 apr 07
Hi Craig,
My take on this is a little different.
> When I cool it fast and keep
> the crystals down it will fit my porcelains. When cooled slowly and there
> is more crystalization, it will craze probably due to the fact that
> crystalline stuff has a higher COE than bright fused glazes.
I suspect the crazing arises not because the crystalline phases
have a higher COE, though they may, but rather that the remaining
glass is depleted of magnesia in the process, and so it has a higher
COE. I'm assuming that the crystals are high in magnesia of course.
Thanx
D
Craig Martell on tue 3 apr 07
D was saying:
>My take on this is a little different.
>I suspect the crazing arises not because the crystalline phases
>have a higher COE, though they may, but rather that the remaining
>glass is depleted of magnesia in the process, and so it has a higher
>COE. I'm assuming that the crystals are high in magnesia of course.
Hello Daniel:
Well, it's difficult to nail this stuff down. I've never come across any
research or work done on this particular theory. There may be some very
solid stuff somewhere but I sure don't know about it. I'm a potter and I
don't get out all that much. But I have seen this happen with calcium
mattes too where the crystals would be snatching Ca which is actually a
higher expansion oxide.
The crystal possibilities with my glaze are: Enstatite which is a magnesium
silicate, Diopside a calcium/magnesium silicate and Wollastonite or calcium
metasilicate. Might be some others too but those are the most likely I
think. Cordierite is another possibility. Enstatite and Diopside are
Pyroxenes (Strangers to the Fire) if that's of any interest.
What happens, I think, is that the crystals will pull not only MgO, CaO
from the glass but also silica. Then you perhaps have a two edged sword
scenario where the crystals have a higher COE because crystalline silica
has a higher COE than fused silica and the glass has been robbed of silica
and also has a higher COE. It could be one of the two possibilities or
perhaps both that cause the COE change in a crystalline glaze. I don't
think I'm going to bust my butt trying to figure it all out though. I'd be
better paid making pots if you know what I mean. I think you do!!
regards, Craig Martell Hopewell, Oregon
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