Earl Krueger on sat 29 mar 08
"Ceramic Science for the Potter"
Lawrence and West
ISBN 1889250242
Ron Roy mentioned this one in passing
a while back so I bought a copy and
learned a few things in my first read-through.
I now understand better about black coring and
iron oxide acting as a flux in reducing atmospheres.
Floculation, defloculation and their effects
are a little more intuitive to me.
The constituents of a good clay body and
why they are there was enlightening.
Why flameware is easy to make but yet
difficult to produce reliably was surprising.
And is your "Ovenware" really save?
And so forth.
The book is dated but there is still a lot
that can be learned from it.
Ron, how about writing an updated version
for those of us who kneed to know?
Earl Krueger
Elmira, Oregon, usa
Ivor and Olive Lewis on sun 30 mar 08
Dear Earl Krueger,
Yes, "Ceramic Science For the Potter" contains remarkable information =
but much of the research done by the two authors is dated, well over =
fifty years old. If you wish to get up to date I suggest you read the =
"Science of Whiteware" Papers which record the work of Prof. William M. =
Carty of Alfred and others
What I find interesting is that their work is ignored by many other =
commentators. What do you make of their conclusions relating to the =
plastic properties of clay, page 80. My interpretation is that under the =
influence of clay, fluid water changes into a solid material.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Earl Krueger on sun 30 mar 08
Dear Ivor Lewis,
You are correct, A lot of time has elapsed
since this book was written and I'm sure
there is greater understanding now of
plasticity in clay. Perhaps someone will
gather together what is currently known
and publish a potters synopsis for us.
I don't have a personal theory about how
water and clay particles interact, or even
a hypotheses. All I have are some ideas
and thoughts on the subject based on my
limited knowledge of chemistry and physics.
Perhaps you would like to perform a thought
experiment with me on the subject.
Let's assume there is a single clay platelet,
with no water or other atoms or molecules
attached to it, existing in an otherwise empty
but bounded free space.
I believe the evidence is sufficient for us to
accept that this particle has the form of a
flat platelet with electrical charge points
dispersed around it's edges. I also believe
the evidence indicates that the flat surfaces
of the platelet are, for the most part,
electrically neutral. This fits well with my
physical understanding of electrical charges
collecting at edges and sharp points. I do
not believe that we can assume these are
full unit charges but are partial charges due
to the formation of molecular electron
probability orbitals.
Now suppose we inject a few molecules of
water into the free space surrounding the
clay platelet. It is undeniable that water
molecules are electrically polar in nature,
therefore they will be attracted to the edges
of the clay platelet by the charges that
exist at those points. As they closely
approach the clay they will be bound to
it by Van der Walls forces. Eventually,
as we inject more and more water into
the free space the clay charge points will
become fully occupied forming a ring of
water around the clay particle.
Due to the polar nature and flexibility of
the water molecule it would be safe to
assume that this ring of water will also
show signs of polarity. As more water
is introduced to the system it will eventually
form a doughnut surrounding the clay
platelet, or as Lawrence, West and others
call it "a water hull".
If we add enough water to completely fill
the bounded free space we could expect
to see a gradient develop from free flowing
water far removed from the clay platelet to
"rigid" water in the area immediately
surrounding the clay.
One could modify this experiment by
introducing two, or more, clay platelets
into the free space at the beginning in
which case the initial injection of water
may cause the edges of the clay particles
to bind together with a small water layer in
between creating a flat sheet.
Lawrence and West propose that the
addition of various cations into the
structure of water surrounding a clay
particle explains a change in plasticity.
I do have trouble accepting their
mechanism and arguments on this
but don't have any other plausible
explanation to offer for your consideration.
Unfortunately attempting these thought
experiments would require stretching my
cognitive powers and knowledge beyond
their limits.
Respectfully,
Earl Krueger
Elmira, Oregon, usa
William & Susan Schran User on sun 30 mar 08
On 3/30/08 2:11 AM, "Ivor and Olive Lewis" wrote:
> If you wish to get up to date I suggest you read the "Science of Whiteware"
> Papers which record the work of Prof. William M. Carty of Alfred and others
Ivor,
I heard Prof. Carty speak at NCECA 2007, but a meeting with some colleagues
caused me to arrive late. He spoke about the idea of aging clay and said
after a certain short amount of time the clay will reach it's maximum
plastic nature.
Have a colleague that mixes his porcelain as slip, then dries to plastic
state, pugs, then uses. This process must wet all of the particles more
completely than just machine mixing and pugging.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Steve Mills on sun 30 mar 08
Bill,
I add a half cup of live (cider) vinegar to the slop mix to accelerate souring and hang it up in bags to dry. When it's ready I can throw it 'round corners.
Steve
Bath
UK
William & Susan Schran User wrote:
On 3/30/08 2:11 AM, "Ivor and Olive Lewis" wrote:
> If you wish to get up to date I suggest you read the "Science of Whiteware"
> Papers which record the work of Prof. William M. Carty of Alfred and others
Ivor,
I heard Prof. Carty speak at NCECA 2007, but a meeting with some colleagues
caused me to arrive late. He spoke about the idea of aging clay and said
after a certain short amount of time the clay will reach it's maximum
plastic nature.
Have a colleague that mixes his porcelain as slip, then dries to plastic
state, pugs, then uses. This process must wet all of the particles more
completely than just machine mixing and pugging.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
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Ron Roy on mon 31 mar 08
Hi Earl,
Well thanks for thinking I could do it but I don't think I have enough
understanding - maybe 4 or 5 of us could do it.
RR
>"Ceramic Science for the Potter"
>Lawrence and West
>ISBN 1889250242
>
>Ron Roy mentioned this one in passing
>a while back so I bought a copy and
>learned a few things in my first read-through.
>
>I now understand better about black coring and
>iron oxide acting as a flux in reducing atmospheres.
>
>Floculation, defloculation and their effects
>are a little more intuitive to me.
>
>The constituents of a good clay body and
>why they are there was enlightening.
>
>Why flameware is easy to make but yet
>difficult to produce reliably was surprising.
>And is your "Ovenware" really save?
>
>And so forth.
>
>The book is dated but there is still a lot
>that can be learned from it.
>
>
>Ron, how about writing an updated version
>for those of us who kneed to know?
>
>
>Earl Krueger
>Elmira, Oregon, usa
>
>______________________________________________________________________________
>Clayart members may send postings to: clayart@lsv.ceramics.org
>
>You may look at the archives for the list, post messages, change your
>subscription settings or unsubscribe/leave the list here:
>http://www.acers.org/cic/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Ivor and Olive Lewis on mon 31 mar 08
Dear William Schran,=20
If you have not read "Ceramic Science for the Potter" by Lawrence and =
West I suggest you borrow a copy. Important information about plasticity =
is given in his conclusions in the section on Plasticity. See Ch 5, page =
80. It would also pay you to borrow some of his references, particularly =
"Clay Mineralogy" by R. E. Grim.
Relating to W. Carty. He and others, particularly G. Y Onoda contributed =
papers to the first and second conferences on the "Science of =
Whitewares". American Ceramic Society published proceedings of these =
meetings. They say a lot of things but ignore Grim.
If you read M. Cardew, you will get a good appraisal of the various ways =
of preparing clay from dry materials. As I see it, the best plastic clay =
is made by the "Slop method" with a long slake under water. The worst =
would be where dry materials are poured into a minimum amount of water =
and then pummelled in a machine.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
<colleagues caused me to arrive late. He spoke about the idea of aging =
clay and said after a certain short amount of time the clay will reach =
it's maximum plastic nature. Have a colleague that mixes his porcelain =
as slip, then dries to plastic state, pugs, then uses. This process must =
wet all of the particles more completely than just machine mixing and =
pugging.>>
Ivor and Olive Lewis on mon 31 mar 08
Dear Steve Mills=20
I appreciate you joining in on this thread. Regarding you comment << =
Bill, I add a half cup of live (cider) vinegar to the slop mix to =
accelerate souring and hang it up in bags to dry. When it's ready I can =
throw it 'round corners...>>=20
Why does Vinegar, especially Cider Vinegar improve clay ? Does it =
enhance plasticity ? If your clay becomes more plastic does it resist =
or succumb to the effects of Gravity when you are throwing tall pots ?
I would be interested to learn your answers to these questions.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Ivor and Olive Lewis on tue 1 apr 08
Dear Earl Krueger.
I appreciate you thoughts. Would that others had been equally creative =
towards this subject we might all have had a better understanding =
earlier in our careers with clay.
When I first came to this subject to this topic I reached the same =
conclusion, that water molecules would form a doughnut ring around the =
periphery of the clay crystals. This is an attractive model because =
when you assemble a lot of these entities of similar size you have a =
material that has the ability to deform universally in any direction.
Then I read Grim and studied his molecular models of Kaolinite and =
applied the VSPER (Valency Shell Electron Pair Repulsion) theory to the =
basic molecular unit. This allows for electron activity at the edges as =
per your model, and as shown by Lawrence and West. But the T-O (Silica =
Tetrahedra - Hydrated Alumina Octahedra) structure has faces which have =
positive charges due to the nature of the proton and negative charges =
due to the abundance of oxygen on the other face. If you search out =
photomicrographs of Kaolinite you will notice that it exhibits a pile =
structure of stacked hexagonal plates. So the faces of the crystals have =
prominent cleavage planes.
The work of Carty and Onoda in the Science of Whiteware papers reaches a =
similar conclusion. See William M. Carty, "The Colloidal Nature of =
Kaolinite" pp 101-110 in Science of Whitewares 2.
The next step is to consider the Volumetric rather than the Mass =
relationships of Kaolin and Water in a standard sort of plastic clay. =
The thickness of the water that separates one hex crystal from its =
immediate neighbour is about twice the thickness of the crystal. The =
hard concept to accept is that Water can form a solid structure above =
its freezing point. But again, I suggest you read both Grim and =
Brownell, not forgetting page 80 in Lawrence and West.
Explaining plastic motion is another story.
Best regards
Steve Mills on wed 2 apr 08
Dear Ivor Lewis,
Apologies for not replying sooner; my ISP's been down for a couple of days.
My experience is that Vinegar promotes plasticity in the same way that the old Potter's habit of pee-ing on their recently mixed clay did, it's just it smells nicer.
Urine and Vinegar amongst other acidic materials, accelerate bacterial growth in new clay when added to it, and it is the decomposition of this that increases plasticity, so that instead of just throwing with the water of plasticity, decomposing matter or "slime" is in the mix as well. Not something the squeamish amongst us like to know, but a fact none the less.
As to it's affect on thrown work, I have not noticed any appreciable difference.
I throw quickly and with pretty soft clay as it is.
Best regards
Steve Mills
Ivor and Olive Lewis wrote: Dear Steve Mills
I appreciate you joining in on this thread. Regarding you comment << Bill, I add a half cup of live (cider) vinegar to the slop mix to accelerate souring and hang it up in bags to dry. When it's ready I can throw it 'round corners...>>
Why does Vinegar, especially Cider Vinegar improve clay ? Does it enhance plasticity ? If your clay becomes more plastic does it resist or succumb to the effects of Gravity when you are throwing tall pots ?
I would be interested to learn your answers to these questions.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
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Bruce Girrell on wed 2 apr 08
Ivor Lewis wrote:
The next step is to consider the Volumetric rather than the Mass relationsh=
ips of Kaolin and Water in a standard sort of plastic clay. The thickness o=
f the water that separates one hex crystal from its immediate neighbour is =
about twice the thickness of the crystal. The hard concept to accept is tha=
t Water can form a solid structure above its freezing point.
Perhaps I could be off base on this. If so, feel free to straighten me out.
Let's just assume for the moment that the model you have called the "ice st=
ructure" is correct. Does the fact that water molucules align in a regular =
structure actually imply that they create a solid? We are accustomed to the=
properties of water in a regular structure that we call ice. But ice does =
not form at room temperature. It requires that the thermal energy available=
to the water molcules be below a certain level. Water in a regular structu=
re with a certain maximum energy behaves as what we know as ice.
If we create a situation (the clay particles) that allows water to take on =
a regular structure at room temperature, why should we assume that it shoul=
d act like ice? Why should we assume that it would be solid in the manner t=
hat we associate with ice? The water molecules have considerably more energ=
y. They may be in a regular structure, and the electrical forces near the c=
lay particles help support that state, but wouldn't it be more likely that =
the regular structure could be broken down much more easily than the struct=
ure of ice?
It seems to me that such a scenario would explain the stiffening that occur=
s as clay is allowed to sit motionless. More water molecules are taken into=
the regular lattice from which they are somewhat reluctant to move, yet it=
is still not a solid in the way that we normally think of a solid. With on=
ly a small amount of additional energy (dropping or wedging the clay), the =
water molecules are easily knocked out of position in the lattice, the regu=
lar structure breaks down quickly, and the clay feels much more plastic.
Comments?
Bruce Girrell
Ivor and Olive Lewis on thu 3 apr 08
Dear Bruce,
Have you read Lawrence and West and Brownell yet ?
Since Wayne Ernest Brownell was at the time of publication of =
"Structural Clay Products" Professor of Ceramic Science at New York =
State College of Ceramics at Alfred University I think he does a far =
better job than I ever could.
Please don't rely on me to simplify the description. Read the texts that =
have provided me with the information.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
<out.
Let's just assume for the moment that the model you have called the "ice =
structure" is correct. Does the fact that water molecules align in a =
regular structure actually imply that they create a solid? We are =
accustomed to the properties of water in a regular structure that we =
call ice. But ice does not form at room temperature. It requires that =
the thermal energy available to the water molecules be below a certain =
level. Water in a regular structure with a certain maximum energy =
behaves as what we know as ice.>>
I suggest you read the contents of the references I give.
Ivor and Olive Lewis on fri 4 apr 08
Dear Steve Mills,
I was intrigued by your suggestion that you are able to "throw the stuff =
round corners"
However....
the old Potter's habit of pee-ing on their recently mixed clay did, it's =
just it smells nicer.>>
........Sounds like experience based on folklore ! Have you ever read of =
any objective evidence to support this view ?
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Steve Mills on fri 4 apr 08
Dear Ivor Lewis,
While I feel that some of the "Folklore" aspects of Ceramics are an interesting starting point for an investigation (the "No smoke without a fire" prompt). I don't view them as gospel without proof.
I am also naturally skeptical of some of the claims made for patented equipment and pet theories. If they sound pausible and might help me, I try them. If they don't work, I reject them.
I prefer always to rely on direct experience.
From 1967 when I started potting full-time I have made up my own clay, only breaking from that for a short time in the late '90s, resuming self making in 03.
Early making was achieved with a Pugmill, and on advice from a fellow maker I added Vinegar to the pugged mix.
Due to the pressures of production there was no time to allow the clay to sit and sour, consequently I saw little or no effect from the addition at that time. The clay was used straight from the Pugmill
Much later I got rid of my third pugmill (I dislike using them for many reasons), and changed to the regime I use now; making my clay up in slop form, pouring it into Terylene (a synthetic cloth) "Trouser Legs", hanging it out to dry off, and then hand wedging it prior to use.
This does allow the clay a short time to "sit".
I had used this technique for a little while before for reclaiming, and after a time had started adding Vinegar to that mix.
This time the effect was noticable. While the reclaim previously was very workable, and an improvement on the pugged mix, the vinegar added mixture was vastly better.
When removed from the trouser-leg, the clay under the surface was almost black, and extremely plastic, requiring very little water or slip to be used while throwing.
For me this was an indication that the addition of vinegar had speeded up the souring process in the comparatively short time allowed for drying off, resulting in a body that was and is a total joy to throw with.
Hence the phrase (a comment from a fellow Potter who tried some of it) that you lit upon.
Best regards
Steve Mills
Ivor and Olive Lewis wrote:
Dear Steve Mills,
I was intrigued by your suggestion that you are able to "throw the stuff round corners"
However....
>
.........Sounds like experience based on folklore ! Have you ever read of any objective evidence to support this view ?
Best regards,
Ivor Lewis.
Redhill,
South Australia.
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Jeanette Harris on sat 5 apr 08
>.
>
>I wonder what the Earwigs are contributing to my clay as they
>scamper around inside the store boxes.
>
>Best regards,
>
>Ivor.
Not too much, Ivor unless you count digested pasteboard and glue.
Could be good.
Jeanette
Who tries to chase them out of her peaches every year.
--
http://jeanetteharrisblog.blogspot.com/
http://www.washingtonpotters.org/members/Jeanette_Harris/wpa_jeanette_harris.htm
http://www.sa-clayartists.org Click on Members, then H
Jeanette Harris
Washingzona
Ivor and Olive Lewis on sat 5 apr 08
Dear Steve Mills,=20
Thank you for your description of preparing clay.=20
Organic activity in Soil, one stage or so before eventual decomposition =
of organic residues into Carbon Dioxide and Water, decays to a dark =
substance called Humus. The basic component of Humus is Humic Acid. =
This, because of the variability of its origins has a variable elemental =
composition of Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus and =
Sulphur. Humus is characterised as a Colloid. Much of it is due to =
Faecal Matter discharged by invertebrate micro-organisms.
I have no doubt that you are experiencing and exploiting the qualities =
of this residue as you throw your clay.
I wonder what the Earwigs are contributing to my clay as they scamper =
around inside the store boxes.
Best regards,
Ivor.
Ivor Lewis.
Redhill,
South Australia.
Steve Mills on sun 6 apr 08
Dear Ivor Lewis,
Thank you for the explanation of what is going on in my clay, I do appreciate that information.
Unfortunately I lack that scientific background; my education gave me a BBC accent, and precious little else!
Take care
Steve
Bath
UK
Ivor and Olive Lewis wrote:
Dear Steve Mills,
Thank you for your description of preparing clay.
Organic activity in Soil, one stage or so before eventual decomposition of organic residues into Carbon Dioxide and Water, decays to a dark substance called Humus. The basic component of Humus is Humic Acid. This, because of the variability of its origins has a variable elemental composition of Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus and Sulphur. Humus is characterised as a Colloid. Much of it is due to Faecal Matter discharged by invertebrate micro-organisms.
I have no doubt that you are experiencing and exploiting the qualities of this residue as you throw your clay.
I wonder what the Earwigs are contributing to my clay as they scamper around inside the store boxes.
Best regards,
Ivor.
Ivor Lewis.
Redhill,
South Australia.
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Ivor and Olive Lewis on mon 7 apr 08
Dear Steve Mills,=20
I may not be correct in my summation of the potential for biological =
activity in clay but Biology was my main subject as I cruised through =
Teacher's College back in the late 1960's. One of the things I =
investigated was the use of Marine Algae as a soil additive. While =
reading for this topic I ran into a lot of information about the =
formation of soils and the genesis of Humic Acid.
Though I have not seen this idea proposed, I imagine using one of the =
Alginate derivatives might enable the preparation of a clay with a high =
degree of plasticity, a high mechanical strength, a relatively low yield =
point and a reduced water content.=20
Such a clay body would not need additions of Bentonite of Halloysite as =
plasticisers.
Now, a question for you. Please would you tell me the quantity of Cider =
Vinegar you add per kilogram of dry clay ?
Have a good week.
Best regards,
Ivor.
Steve Mills on mon 7 apr 08
Dear Ivor Lewis.
For each Trouser Leg I make up 13.8kg of clay (dry weight) at a time in a 5 (UK) Gallon bucket. To this I add enough water to make a thick slip and approximately half a cup (cook's measure) of Vinegar. Sand is included in the mix.
The mixture is a combination of two UK Ball Clays a little China Clay and yellow builder's sand. No Bentonite or similar.
Thank you
Best regards
Steve
Bath
UK
The builders are in and concentration is a rare luxury!
Ivor and Olive Lewis wrote:
Dear Steve Mills,
I may not be correct in my summation of the potential for biological activity in clay but Biology was my main subject as I cruised through Teacher's College back in the late 1960's. One of the things I investigated was the use of Marine Algae as a soil additive. While reading for this topic I ran into a lot of information about the formation of soils and the genesis of Humic Acid.
Though I have not seen this idea proposed, I imagine using one of the Alginate derivatives might enable the preparation of a clay with a high degree of plasticity, a high mechanical strength, a relatively low yield point and a reduced water content.
Such a clay body would not need additions of Bentonite of Halloysite as plasticisers.
Now, a question for you. Please would you tell me the quantity of Cider Vinegar you add per kilogram of dry clay ?
Have a good week.
Best regards,
Ivor.
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Ivor and Olive Lewis on tue 8 apr 08
Dear Steve Mills,=20
Thank you for this precise information.
<in a 5 (UK) Gallon bucket. To this I add enough water to make a thick =
slip and approximately half a cup (cook's measure) of Vinegar. Sand is =
included in the mix.
The mixture is a combination of two UK Ball Clays a little China Clay =
and yellow builder's sand. No Bentonite or similar.>>
Picked up a gallon of generic vinegar this morning so I am ready to make =
up a 20 litre bucket of slop. I will pre-mix my water and vinegar. Will =
report back to you once the slop is dewatered.
Best regards,
Ivor.
Ivor Lewis.
Redhill,
South Australia.
Steve Mills on tue 8 apr 08
Dear Ivor Lewis,
As a matter of interest I usually buy a gallon of the cheapest Cider going (known locally as "Screech" for obvious reasons!), take the lid off, and it's Vinegar within a week!
It's definitely the cheapest option.
Best regards
Steve
Bath
UK
Ivor and Olive Lewis wrote: Dear Steve Mills,
Thank you for this precise information.
<
The mixture is a combination of two UK Ball Clays a little China Clay and yellow builder's sand. No Bentonite or similar.>>
Picked up a gallon of generic vinegar this morning so I am ready to make up a 20 litre bucket of slop. I will pre-mix my water and vinegar. Will report back to you once the slop is dewatered.
Best regards,
Ivor.
Ivor Lewis.
Redhill,
South Australia.
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pdp1@EARTHLINK.NET on tue 8 apr 08
Hi Ivor,
Expect some differences anyway, between differing Vinegars, as for how they
will influence what they are added to -
Especially between 'Raw Apple Cider Vinegar' ( which is a Living Organism in
suspension, ) and 'White Vinegar' ( which is a 'dead' chemical solution )
...but for that matter, also with various others such as 'Balsamic' or
'Rice' and so on...which are usualy the latter, but some may be 'live' also,
so each must be regarded intrinsically according to the exact type.
I have no idea what 'Generic Vinegar' is, other than it will only partially
represent it's broader kind, just as say, getting some 'Generic Clay' or a
'Generic anything' would only
partially or incompletely represent a broader Catagory of item.
So...bear this in mind, as it will probably make a difference.
Best wishes...
Have fun...!
Phil
l v
----- Original Message -----
From: "Ivor and Olive Lewis"
Dear Steve Mills,
Thank you for this precise information.
<5 (UK) Gallon bucket. To this I add enough water to make a thick slip and
approximately half a cup (cook's measure) of Vinegar. Sand is included in
the mix.
The mixture is a combination of two UK Ball Clays a little China Clay and
yellow builder's sand. No Bentonite or similar.>>
Picked up a gallon of generic vinegar this morning so I am ready to make up
a 20 litre bucket of slop. I will pre-mix my water and vinegar. Will report
back to you once the slop is dewatered.
Best regards,
Ivor.
Ivor Lewis.
Redhill,
South Australia.
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