mary simmons on tue 16 nov 99
Mary said: (in the old lithium glazes/petalite line)
>>So, where does Ca, NOT being an alkali, fit in? Are you lumping it in with
>>the alkalis and I am just being sniggly?
>
>
then CRAIG said:
>Are we on the same page? :>) According to my references, and the Periodic
>Table Ca, is a base material. Hamer says the the strong alkalis are Na, K,
>and Li. He places Ca in with the weaker alkalis and calls it an alkaline
>earth.
Probably not--I am not much of a chemist--everything I know about chemistry
comes from geology--I have a small amount of knowledge, with which I can be
quite dangerous!. In my thesis, I carefully distinguished between the
alkalis (Na and K) and Ca, as is also done in the geologic literature.
Maybe I don't know that there is really no difference between alkalis and
alkaline earths. BUT, there are alkali feldspars, which are a series of
compositions of (Na,K)AlSi3O8, whose end members are albite and the K-spars
orthoclase, microcline and sanidine. Then there is the plagioclase series,
whose compositions are between end members albite and anorthite (not a
simple substitution of Ca for Na though--to maintain charge balance, Al and
Si also substitute--albite =NaAlSi3O8 and anorthite = CaAl2Si2O8). Calcium
does not substitute into alkali feldspars, leading me to believe that the
reason these are called alkali feldspars is that Na and K are considered
alkalis. But, believe it or don't I am somewhat simple-minded.
My thesis was about the alteration of a pile of rhyolite via hydrothermal
alteration during or soon after the stuff was erupted, to create kyanite.
To do this, everything has to be taken out of the rhyolite except silica
and alumina (kyanite = AlSi2O5). ANd what has to be taken out that is
present in any kind of way in rhyolites???? Our little friends the
alkalis (Na and K) and Ca.!!!! (oh and some Fe and Mg) I think I proved it
rather convincingly by tracking the depletion of these elements as well as
Fe and Mg, from the edges of these huge pods or lenses of kyanite to the
middle. At the edges, the K2O. Na2O and CaO (wt %) is more or less what
you'd expect from a rhyolite, and were progressively depleted toward the
centers of the pods.
WHy am I telling you all this??? Clues about fluxes? Na, K and Ca are the
most unhappy elements in the crust--they NEVER like where they are and are
always on the move......like in glazes?? They hate being in the mantle and
jump into silicates that are unstable at earth's surface, so they weather
out and become clay......
> If you
>add some Ca to a mix of just feldspar, it starts to work with the KNaO and
>will break down and glass the silica faster and more completely.
AhA!!!! Just as I suspected!!!!!
>There is
>a very strong eutectic point in the proper ratio of any feldspar and
>whiting, or wollastonite so the proof is in the pudding so to speak.
ANY feldspar??? AM I being too bookish to note that not all feldspars have
calcium, and therefore what would they be doing in a phase diagram with
calcite or wollastonite?? Or calcite in a phase diagram with ANY feldpar?
calcite is not a silicate! What am I missing???? A phase diagram I've
never seen??
You
>asked what I meant by spar fusions and this would probably be a good point
>to go into that because I use this tool to find eutectic points with mixes
>of spar and other fluxes.
You do this to find the melting temp of a mixture you want to make a glaze of?
>Gerstley borate isn't a frit.
>It's actucally just ulexite that they pick
>up off the desert floor and crush into powder. It is really varialble. It
>contains Na, Ca and B2O3. It's a strong flux though and is real active at
>raku temps around cone 06.
I thought GB most closely resembles colemanite? ANd, is it so stong
because of the calcium? Or because the Ca is easily liberated from the
borate structure (is it?)
hasta la later,
Mary, in the Wilds of ALbuquerque.....
Mary Simmons
Dept of Earth and Planetary Sciences
Northrop Hall
University of New Mexico
Albuquerque, NM 87131-1116
(505)277-9259
piedra@unm.edu
I.Lewis on thu 18 nov 99
------------------
Mary Simmons in her recent rejoinder to the above subject gave the following
quotation from a previous posting.
=22There is a very strong eutectic point in the proper ratio of any felspar =
and
whiting, or wollastonite so the proof is in the pudding so to speak.=22
Please, could someone explain what a strong eutectic point is?
Since a eutectic point is a precise temperature the quotation seems to be a
nonsense statement. I do not have the mathematical ability to sort out the
Algebra which would enable me to calculate the weights of Wollastonite,
Anorthite and Tridymite which are the mineral components of this eutectic. =
Mind
you, if I could get a samples of Anorthite and Tridymite I might have a go.
In a letter to the Editor of Ceramics Monthly I suggested that those who =
insist
a eutectic is present in any glaze recipe composition should conduct the
following experiment. Calculate the proportions of the necessary oxides for =
the
Calcium oxide, Silicon dioxide, Aluminium oxide system eutectic of 1170C
(2138F). Intimately mix measured portions of these powdered compounds, using=
a
ball mill if you think that finer grain size will enhance your success. Then
heat to the temperature I have given, or slightly above and report to the =
rest
of us what your observations are. I have results for heating this mixture, =
and
other mixtures which contain the other combinations of compounds which =
contain
these three oxides. Observable and reproducible results form the basis of =
stong
arguaments.
Ivor Lewis. In the spirit of Scientific Empiricism. Or sweet lemons.
mary simmons on fri 19 nov 99
Hi Ivor-
By now, there are probably several hundred responses to your
question......but here's mine, (because my name is the first word in your
post!) maybe "precise" and "strong" eutectic points are synonymous? Leave
us NOT mince words, nor argue too strenuously about semantics....
But, as a geologist and a person who pays complete attention to details:
whiting is calcite (CaCO3), tho I've heard some say there can be a bit of
Mg in there as well, making whiting a calcite/dolomite mineral.
Wollastnonite (CaSiO3)is a pyroxenoid--the Large amount of Ca stuffed into
a pyroxene structure warps it, but not so much as to make it completely
unlike a pyroxene (recall that spodumene is a Li-rich pyroxene. Feldspars
are alumino-silicates, anorthite is the Ca-rich end-member of the
plagioclase series (Na,Ca)Si3O8. To the best of my knowledge there is no
tridymite in any of these minerals. Tridymite is a polymorph of quartz, and
equilibrates at high temperature and pressures up to 20 kilobars (20 kbar
is VERY deep in the crust)--it is found in volcanic rocks, but not in
quantities that are identifiable with the naked eye. So, you'd have a hard
time finding enough tridymite to do anything with.....
I am afraid to say that it takes much more than algebra to figure out these
eutectics--one must delve into the dreaded calculus and thermodynamics,
locating the Gibb's Free Energy planes and such, which are based on
compositions and temperature and other things that I am sure most people
don't want to know about........
OR-
Then there is the REAL, experimental world, a happenin' kind of place that
blows young scientists (especially geologists) minds, because we so expect
math and science to be precise. Ha! Many a mathematically derived phase
diagram has ended up on the slag heap, when experimental results proved it
wrong. Math is an approximation (but please DON'T tell those people in
that other building that!)
>In a letter to the Editor of Ceramics Monthly I suggested that those who
>insist
>a eutectic is present in any glaze recipe composition
How can there NOT be?
I have sitting here leering at me, FOUR volumes of _Phase Diagrams for
Cermists_ published by the American Ceramic Society--which reports
eutectics for more systems than my teeny tiny brain can comprehend. These
eutectics were EXPERIMENTALLY derived......
>I have results for heating this mixture, and
>other mixtures which contain the other combinations of compounds which
contain
>these three oxides.
>Observable and reproducible results form the basis of stong
>arguaments.
Ja.....so, tell us YOUR results!!! You could make a big name for yourself,
if you can stand the American Ceramic Society on it's head!
Mary
Mary Simmons
Dept of Earth and Planetary Sciences
Northrop Hall
University of New Mexico
Albuquerque, NM 87131-1116
(505)277-9259
piedra@unm.edu
John Hesselberth on sat 20 nov 99
Hi Mary and Ivor,
I think there is a fairly straight-forward reconcile between your two
points of view. Thermodynamics describes what a system looks like at
equilibrium or, alternatively, how far it is from equilibrium and how
much energy it may require or give off to reach equilibrium. Eutectics
are on example of something that exist at equilibrium. So are crystals
and a particular mix of chemical compounds. Thermodynamics, however,
teaches nothing about the rate at which you can approach or achieve
equilibrium.
Unfortunately (actually fortunately from a potter's viewpoint), in
potter-land we rarely, if ever, reach an equilibrium state when we are
firing our pots. We, to be direct about it, heat a pot/glaze up until we
get some stuff that kind of looks like glass on the surface of the pot
and then quickly freeze it off before bad things start to happen. Yes,
sometimes we soak at temperature for an hour or two, but that probably
doesn't even come close to achieving an equilibrium state. I would guess
reaching equilibrium would take days, weeks or even years at temperature.
If were to wait for equilibrium all sorts of terrible things would start
to happen. For example we might form lots of cristoballite and have to
bear the consequences of all the problems it can cause. Or our glaze
might become perfectly homogeneous and, therefore, ugly and boring (it is
usually the non-uniformities in a glaze that give it character or beauty.
Those non-uniformities also let me keep a "sealer" glaze on top of a high
leaching glaze). Or it might just run off the pot and end up on the
shelf of our kiln. And there are probably a host of other things
equilibrium would bring of which potters are not really terribly fond.
Since we don't achieve equilibrium, we probably never achieve true
eutectics in our glazes except maybe for a few molecules or a tiny
crystal here and there scattered throughout the glaze that manage to
arrange themselves in that fashion before we freeze them off. In a
carefully controlled laboratory environment eutectics do indeed exist as
shown in the phase diagrams--just not to any significant degree in what
potters make.
The minerals we work with, on the other hand, probably had lots of time
at very high temperature (like maybe centuries or millenia in some
cases?? you know those facts far better than I) so they are near their
equilibrium states (and are boringly homogeneous from a potter's
perspective).
In short, we are dealing with a very dynamic system which acts under the
driving forces established by the thermodynamics of the system, but we
never let it go to completion. Isn't it great!!! That's what makes it
so much fun and, at the same time, so frustrating.
John
m
>
>Then there is the REAL, experimental world, a happenin' kind of place that
>blows young scientists (especially geologists) minds, because we so expect
>math and science to be precise. Ha! Many a mathematically derived phase
>diagram has ended up on the slag heap, when experimental results proved it
>wrong. Math is an approximation (but please DON'T tell those people in
>that other building that!)
>
>>In a letter to the Editor of Ceramics Monthly I suggested that those who
>>insist
>>a eutectic is present in any glaze recipe composition
>
>How can there NOT be?
>I have sitting here leering at me, FOUR volumes of _Phase Diagrams for
>Cermists_ published by the American Ceramic Society--which reports
>eutectics for more systems than my teeny tiny brain can comprehend. These
>eutectics were EXPERIMENTALLY derived......
>
>
>>I have results for heating this mixture, and
>>other mixtures which contain the other combinations of compounds which
>contain
>>these three oxides.
>>Observable and reproducible results form the basis of stong
>>arguaments.
John Hesselberth
Frog Pond Pottery
P.O. Box 88
Pocopson, PA 19366 USA
EMail: john@frogpondpottery.com web site: http://www.frogpondpottery.com
"It is time for potters to claim their proper field. Pottery in its pure
form relies neither on sculptural additions nor on pictorial decorations.
but on the counterpoint of form, design, colour, texture and the quality
of the material, all directed to a function." Michael Cardew in "Pioneer
Pottery"
mary simmons on sun 21 nov 99
Hi John and Ivor and Craig and Earl and Elizabeth and .......?
you are right of course, John...
It is SO exasperating that we speak of these melt/crystallization processes
(both ceramic and igneous) as if there were such thing as an equilibrium
state ANYWHERE. I think the reason why we do this is because it makes the
math easier (I am ALL for that!!)--though at it's easiest, this math is
just a wee bit beyond what I am lazily comfortable with. But it does help
to be able to make SOME kind of stab at melting temperatures of various
mixtures, even if there is no real equilibrium and really no such thing as
pure phases (except in theory). I know from my own experience in analyzing
loads of rocks for their chemistry, that there are ALWAYS a few uninvited
passengers that can really foul these tidy theories up.
I took home those phase diagrams of the American Ceramic Society--GREAT
instructions on how to read phase diagrams!!--and the point was made there
that these univited passengers can cause the eutectic point to shift--and
I'd bet that THIS is what Ivor is talking about: theoretical phase
diagrams are based on systems of pure end-member phases. Experimental
phase diagrams are based on the compositions of the materials that are IN
the mixture being tested. Because there is some degree of variation in
glaze materials, the published phase diagrams are probably NOT what we'd
get in our own laboratories (kilns), because we are using a different
composition of materials.
I really don't know how much effect the small amount of univited guests
make in a glaze--I KNOW that they have to be taken into account, but I
wonder how MUCH? Is it enough that it is necessary to know the chemical
analysis of each new batch of glaze components????
Equilibrium in igneous and metamorphic processes within the earth's crust
is as likely as it is in the kiln. NOT! If there were equilibrium
conditions present at all times during metamorphic porcess, f'rinstance,
then there would be quite a bit LESS diversity in rock types on the surface
of the earth. As rocks are being uplifted through tectonics or erosion,
those that equilibrated at depth are undergoing changes in pressure and
temperature on their way up to the surface. According to equlibrium
theory, these rocks should change their structures to accomodate each new
pressure and temperature. But they don't. We have all sorts of really
beautiful rocks at the surface--diamonds for example--that are out of
equilibrium and definitely NOT re-equilibrating to surface conditions.
Assuming equilibrium makes the math easier, and the system easier to
understand, though this assumption should make us all skeptical, eh Ivor?
There is something deeply philosophically comforting to me, that the state
of non-equilibrium makes more interesting glazes AND prettier rocks!
Viva Voodoo!
Mary
Mary Simmons
Dept of Earth and Planetary Sciences
Northrop Hall
University of New Mexico
Albuquerque, NM 87131-1116
(505)277-9259
piedra@unm.edu
Earl Brunner on mon 22 nov 99
Hey, YOu might have addressed this in part to me, but you are not even talking
the same language I speak (probably ignorance on my part but clueless just the
same)
theoretical phase diagrams are based on systems of pure end-member phases.
---Indeed!
mary simmons wrote:
> ----------------------------Original message----------------------------
> Hi John and Ivor and Craig and Earl and Elizabeth and .......?
>
> you are right of course, John...
>
> It is SO exasperating that we speak of these melt/crystallization processes
> (both ceramic and igneous) as if there were such thing as an equilibrium
> state ANYWHERE. I think the reason why we do this is because it makes the
> math easier (I am ALL for that!!)--though at it's easiest, this math is
> just a wee bit beyond what I am lazily comfortable with. But it does help
> to be able to make SOME kind of stab at melting temperatures of various
> mixtures, even if there is no real equilibrium and really no such thing as
> pure phases (except in theory). I know from my own experience in analyzing
> loads of rocks for their chemistry, that there are ALWAYS a few uninvited
> passengers that can really foul these tidy theories up.
>
> I took home those phase diagrams of the American Ceramic Society--GREAT
> instructions on how to read phase diagrams!!--and the point was made there
> that these univited passengers can cause the eutectic point to shift--and
> I'd bet that THIS is what Ivor is talking about: theoretical phase
> diagrams are based on systems of pure end-member phases. Experimental
> phase diagrams are based on the compositions of the materials that are IN
> the mixture being tested. Because there is some degree of variation in
> glaze materials, the published phase diagrams are probably NOT what we'd
> get in our own laboratories (kilns), because we are using a different
> composition of materials.
>
> I really don't know how much effect the small amount of univited guests
> make in a glaze--I KNOW that they have to be taken into account, but I
> wonder how MUCH? Is it enough that it is necessary to know the chemical
> analysis of each new batch of glaze components????
>
> Equilibrium in igneous and metamorphic processes within the earth's crust
> is as likely as it is in the kiln. NOT! If there were equilibrium
> conditions present at all times during metamorphic porcess, f'rinstance,
> then there would be quite a bit LESS diversity in rock types on the surface
> of the earth. As rocks are being uplifted through tectonics or erosion,
> those that equilibrated at depth are undergoing changes in pressure and
> temperature on their way up to the surface. According to equlibrium
> theory, these rocks should change their structures to accomodate each new
> pressure and temperature. But they don't. We have all sorts of really
> beautiful rocks at the surface--diamonds for example--that are out of
> equilibrium and definitely NOT re-equilibrating to surface conditions.
>
> Assuming equilibrium makes the math easier, and the system easier to
> understand, though this assumption should make us all skeptical, eh Ivor?
>
> There is something deeply philosophically comforting to me, that the state
> of non-equilibrium makes more interesting glazes AND prettier rocks!
>
> Viva Voodoo!
> Mary
>
> Mary Simmons
> Dept of Earth and Planetary Sciences
> Northrop Hall
> University of New Mexico
> Albuquerque, NM 87131-1116
>
> (505)277-9259
> piedra@unm.edu
--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec@anv.net
mary simmons on tue 23 nov 99
Hi Earl, Gavin, John, Craig, Elizabeth, and????-
Wellllllll, I sent that post to whoever is interested in reading it--and
was responding to the discussion.......
Pure end-member phases are minerals such as anorthite and albite--both are
"end members" in the plagioclase feldpsar series. "Pure end member" means
that there are no pesky uninvited guests--that is anorthite is CaAl2Si208
and albite is NaAlSi3O8. It would be very unusual and uncommon for us to
find minerals so pure--it is more likely that you'd get something with a
little Na and a little Ca and whatever else might be able to stow away in
the plagioclase feldspar structure.
This is not limited to feldspars, neither......a lot of minerals belong to
"systems" where they can accomodate a limited number of different elements.
Pyroxenes are such a system--where the "end members" are pure MgSiO3,
FeSiO3, and CaSiO3. THere is a limited "series" between these "end-member"
phases, where for example Fe and Mg can substitute for one another and
still be bonded to the SiO3 stuff, so you'd have almost a complete "solid
solution" between Fe and Mg. Solid solution means that a mineral can have
a combination of the elements that compose it's end-members, ie you get ONE
mineral. Mg and Fe are about the same size and have the same charge
(1+)--which is why they can do this--this mineral series is in between pure
end member enstatite (MgSiO3) and ferrosilite (FeSiO3). Ca, on the other
hand is LARGE and has a charge of 2+, even so, up to 50% Ca, a pyroxene
with Ca, Mg (AND Fe) can be had (diopside to hedenbergite series =
Ca(Mf,Fe)Si21O6.) 100% Ca in this system is a "pyroxenoid"--because to
accomodate the large Ca the structure has to distort.....this mineral is
wollastonite (CaSiO3).
It is those univited passengers that foul up the phase diagrams that are
based on mathematical and thermodynamic calculations. THese guests will be
along in a variety of concentrations, which to us means that each bag of
any old glaze material we use would have a different amount of the
interlopers--so even the phase diagrams that are built by experiment would
not be 100% accurate for every batch of that material.
Because I am more a geologist at the moment than a potter, I lack
experience in what glaze materials will do to (and with) each other in the
kiln. I want to draw on the knowledge that I have of geology and apply it
to glaze chemistry. Phase diagrams are not the
infinite-God-ultimate-truth, because of the intrinsic variation in
minerals, but they DO provide a starting point as well as an approximation
of the behavior of mixtures of minerals and oxides we use.
At some point we all hit the wall with this stuff. The wall is where I
can't understand any more. I throw up my hands in despair at my dull wits.
Each time I think about these things, or read another page in "Phase
Diagrams for Idiots" my understanding increases. But so does my awareness
of how much I don't know, and there's that damn wall again!!!
Some people call that wall voodoo......whatever....it IS that place where I
am lost. Makes me want to run away......but I ALWAYS come back
I try to maintain a balance between the "pure end members" art and science.
I DO believe that they are connected. It is in such artful endeavors as
pottery where we see science and art interact in a glorious dance.......
lost, and spaced
Mary
Mary Simmons
Dept of Earth and Planetary Sciences
Northrop Hall
University of New Mexico
Albuquerque, NM 87131-1116
(505)277-9259
piedra@unm.edu
Earl Brunner on wed 24 nov 99
You are an interesting read. The scarry thing is I think I almost understand
what you are saying, at least the general gist of it. But basically I tthink I
hit that vodoo wall way, way before you do.
In my terms I think you are saying that when we try tp predict the interactions
of two or more chemicals and /or raw materials we are limited in our ability to
predict by the imperfections or impurities in the materials and their influence
on the melt. And that some of these can screw up the works even in small
percentages as the raw materials vary from batch to batch.
Is that basically it?
mary simmons wrote:
> ----------------------------Original message----------------------------
> Hi Earl, Gavin, John, Craig, Elizabeth, and????-
>
> Wellllllll, I sent that post to whoever is interested in reading it--and
> was responding to the discussion.......
>
> Pure end-member phases are minerals such as anorthite and albite--both are
> "end members" in the plagioclase feldpsar series. "Pure end member" means
> that there are no pesky uninvited guests--that is anorthite is CaAl2Si208
> and albite is NaAlSi3O8. It would be very unusual and uncommon for us to
> find minerals so pure--it is more likely that you'd get something with a
> little Na and a little Ca and whatever else might be able to stow away in
> the plagioclase feldspar structure.
>
> This is not limited to feldspars, neither......a lot of minerals belong to
> "systems" where they can accomodate a limited number of different elements.
> Pyroxenes are such a system--where the "end members" are pure MgSiO3,
> FeSiO3, and CaSiO3. THere is a limited "series" between these "end-member"
> phases, where for example Fe and Mg can substitute for one another and
> still be bonded to the SiO3 stuff, so you'd have almost a complete "solid
> solution" between Fe and Mg. Solid solution means that a mineral can have
> a combination of the elements that compose it's end-members, ie you get ONE
> mineral. Mg and Fe are about the same size and have the same charge
> (1+)--which is why they can do this--this mineral series is in between pure
> end member enstatite (MgSiO3) and ferrosilite (FeSiO3). Ca, on the other
> hand is LARGE and has a charge of 2+, even so, up to 50% Ca, a pyroxene
> with Ca, Mg (AND Fe) can be had (diopside to hedenbergite series =
> Ca(Mf,Fe)Si21O6.) 100% Ca in this system is a "pyroxenoid"--because to
> accomodate the large Ca the structure has to distort.....this mineral is
> wollastonite (CaSiO3).
>
> It is those univited passengers that foul up the phase diagrams that are
> based on mathematical and thermodynamic calculations. THese guests will be
> along in a variety of concentrations, which to us means that each bag of
> any old glaze material we use would have a different amount of the
> interlopers--so even the phase diagrams that are built by experiment would
> not be 100% accurate for every batch of that material.
>
> Because I am more a geologist at the moment than a potter, I lack
> experience in what glaze materials will do to (and with) each other in the
> kiln. I want to draw on the knowledge that I have of geology and apply it
> to glaze chemistry. Phase diagrams are not the
> infinite-God-ultimate-truth, because of the intrinsic variation in
> minerals, but they DO provide a starting point as well as an approximation
> of the behavior of mixtures of minerals and oxides we use.
>
> At some point we all hit the wall with this stuff. The wall is where I
> can't understand any more. I throw up my hands in despair at my dull wits.
> Each time I think about these things, or read another page in "Phase
> Diagrams for Idiots" my understanding increases. But so does my awareness
> of how much I don't know, and there's that damn wall again!!!
>
> Some people call that wall voodoo......whatever....it IS that place where I
> am lost. Makes me want to run away......but I ALWAYS come back
>
> I try to maintain a balance between the "pure end members" art and science.
> I DO believe that they are connected. It is in such artful endeavors as
> pottery where we see science and art interact in a glorious dance.......
>
> lost, and spaced
> Mary
>
> Mary Simmons
> Dept of Earth and Planetary Sciences
> Northrop Hall
> University of New Mexico
> Albuquerque, NM 87131-1116
>
> (505)277-9259
> piedra@unm.edu
--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec@anv.net
mary simmons on thu 25 nov 99
Earl and everyone else reading....
>You are an interesting read. The scarry thing is I think I almost understand
>what you are saying, at least the general gist of it. But basically I
tthink >I hit that vodoo wall way, way before you do.
I'd bet you DO understand more than you think! I am also in awe that I
have been able to come this far in a science! And I HOPE that all the
time/years/tears I've spent paid off a little and made that wall a bit
further away than it was to begin with. I was not born knowing any of
this, and truth be told I am much more an artist than a scientist, so it's
been a long hard road. But the payoff is so satistfying!! I also have
this pesky curiousity and a passionate love for rocks and earth processes.
And now I am at the threshold of a whole new wonderful world of pottery,
where my knowledge of rocks and minerals can only propel me forward.
The important thing (or at least ONE of them) for us to realize is that we
all use chemistry and math in our daily lives and are not aware of it (eh,
Mel?). Everyone who works in pottery has some degree of understanding of
the technology in this endeavor--and THAT creates a context for other bits
of imformation that we encounter, each bit of info that finds it's way
there moves the wall back. If you don't have a context in which to place
information, then it is really hard to understand it. I think this
discussion is helping us all to build that context, or at least to add to
it. I am benefitting GREATLY by everyone's input.
FEAR NOT! Most of us did develop fear of math and science at an early age,
and convinced ourselves that we are just stupid--(and I am the Queen of
Feeling Stupid) and panic when we hit the wall. Courage is going on
ANYWAY.....
>In my terms I think you are saying that when we try tp predict the
>interactions of two or more chemicals and /or raw materials we are limited
in >our ability to predict by the imperfections or impurities in the
materials and >their influence on the melt. And that some of these can
screw up the works >even in small percentages as the raw materials vary
from batch to batch.
>Is that basically it?
that is EXACTLY it!!!! All this discussion about eutectics and phase
diagrams leads to being able to make predictions about the behavior of
"imperfect" earth materials in a glaze. We want things to be somewhat
predictable, so that we can, among other things, depend on a new batch of
glaze to be more or less the same as the last one. Which is why it must be
important to know what we are using!
It is also good to realize that the theoretical nature of phase diagrams
and the theorectical compositions of rocks and minerals must be tempered
with experiments and testing, as Mel and Ron Roy and Tony Hansen and others
are continually reminding all of us. Whether or not you understand the
wild ride through a phase diagram does not impair your ability to
understand this stuff through experimentation--there is more than one path
through these woods!
Speaking of which, I am about to post the results of a chemical analysis I
did yesterday on my batch of gerstley borate, which may well be one of the
most UN-predictable glaze material around.
cheers to all-
Mary
Mary Simmons
Dept of Earth and Planetary Sciences
Northrop Hall
University of New Mexico
Albuquerque, NM 87131-1116
(505)277-9259
piedra@unm.edu
Earl Brunner on sat 27 nov 99
One of the really attractive things about pottery to me back when I was in High
school looking at a career in it was the fact that I didn't have to take as many
math classes in my BFA program. So I got to college and then found out about
glazes. This was before personal computers, before pocket calculators, Rhodes
book on clay and glazes was the glaze bible of choice. I think I started out
doing the math with a slide rule. It was the pits. I did the math and learned
because I was motivated. It had a real life application that I was interested
in. More than my High school teachers managed to convey.
mary simmons wrote:
> ----------------------------Original message----------------------------
> Earl and everyone else reading....
>
> >You are an interesting read. The scarry thing is I think I almost understand
> >what you are saying, at least the general gist of it. But basically I
> tthink >I hit that vodoo wall way, way before you do.
>
> I'd bet you DO understand more than you think! I am also in awe that I
> have been able to come this far in a science! And I HOPE that all the
> time/years/tears I've spent paid off a little and made that wall a bit
> further away than it was to begin with. I was not born knowing any of
> this, and truth be told I am much more an artist than a scientist, so it's
> been a long hard road. But the payoff is so satistfying!! I also have
> this pesky curiousity and a passionate love for rocks and earth processes.
> And now I am at the threshold of a whole new wonderful world of pottery,
> where my knowledge of rocks and minerals can only propel me forward.
>
> The important thing (or at least ONE of them) for us to realize is that we
> all use chemistry and math in our daily lives and are not aware of it (eh,
> Mel?). Everyone who works in pottery has some degree of understanding of
> the technology in this endeavor--and THAT creates a context for other bits
> of imformation that we encounter, each bit of info that finds it's way
> there moves the wall back. If you don't have a context in which to place
> information, then it is really hard to understand it. I think this
> discussion is helping us all to build that context, or at least to add to
> it. I am benefitting GREATLY by everyone's input.
>
> FEAR NOT! Most of us did develop fear of math and science at an early age,
> and convinced ourselves that we are just stupid--(and I am the Queen of
> Feeling Stupid) and panic when we hit the wall. Courage is going on
> ANYWAY.....
>
> >In my terms I think you are saying that when we try tp predict the
> >interactions of two or more chemicals and /or raw materials we are limited
> in >our ability to predict by the imperfections or impurities in the
> materials and >their influence on the melt. And that some of these can
> screw up the works >even in small percentages as the raw materials vary
> from batch to batch.
> >Is that basically it?
>
> that is EXACTLY it!!!! All this discussion about eutectics and phase
> diagrams leads to being able to make predictions about the behavior of
> "imperfect" earth materials in a glaze. We want things to be somewhat
> predictable, so that we can, among other things, depend on a new batch of
> glaze to be more or less the same as the last one. Which is why it must be
> important to know what we are using!
>
> It is also good to realize that the theoretical nature of phase diagrams
> and the theorectical compositions of rocks and minerals must be tempered
> with experiments and testing, as Mel and Ron Roy and Tony Hansen and others
> are continually reminding all of us. Whether or not you understand the
> wild ride through a phase diagram does not impair your ability to
> understand this stuff through experimentation--there is more than one path
> through these woods!
>
> Speaking of which, I am about to post the results of a chemical analysis I
> did yesterday on my batch of gerstley borate, which may well be one of the
> most UN-predictable glaze material around.
>
> cheers to all-
> Mary
>
> Mary Simmons
> Dept of Earth and Planetary Sciences
> Northrop Hall
> University of New Mexico
> Albuquerque, NM 87131-1116
>
> (505)277-9259
> piedra@unm.edu
--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec@anv.net
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