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## - a packing density question

### Ivor and Olive Lewis on mon 2 apr 07

Are there not mathematical rules that describe the packing density of =
uniform spheres. For example, if the arrays are centred on a square grid =
system there is more free space than if they are arranged as an =
hexagonal array. Was this not the Kepler Conjecture, a notion that is =
difficult to prove which has an answer known to every Green Grocer who =
displays Apples and Oranges.
It should also be possible to calculate the diameter of balls that will =
fit tangentially within the spaces created by open or close packing the =
larger spheres.
By the time you get the third smaller spheres and insert some dominoes =
there would be insufficient space for water. So motion would not be an =
issue.

Perhaps it is time to examine and image real plastic systems rather than =
consider hypothetical constructs.
Best regards,

Ivor

### Lynne and Bruce Girrell on mon 2 apr 07

Ivor Lewis wrote:

>Can you give us an expansion of the cyphers you are using for these
>peculiar clay qualities. >Without knowing your code I am lost.

Sorry Ivor. We started using some shorthand.
PSD = Particle size distribution
GPD = Green packing density

components as opposed to spheres - The spheres are only being used a thought
experiment to show how smaller particles easily fill the interstitial spaces
remaining when large particles are packed. There was no intention for the
spheres to represent how the actual physical system would work.

Cheers,

Bruce Girrell

_________________________________________________________________
5.5%* 30 year fixed mortgage rate. Good credit refinance. Up to 5 free
quotes - *Terms

### WJ Seidl on mon 2 apr 07

Ivor:
I believe you are on to something here.
Perhaps an examination (under a microscope of a power I can only dream of
) of the same clay body, in a short state and in a plastic state would
yield some valuable clues as to the nature of the truth in what we are all
saying. We can easily get to the bottom of this. Once short and plastic has
been examined, then a sample put aside for aging, and a comparison made as
well. Examine all the variables, decide what is happening.

Does anyone have an electron microscope hanging around?
Best,
Wayne Seidl

-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Ivor and Olive
Lewis
Sent: Monday, April 02, 2007 3:15 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: - a packing density question

Are there not mathematical rules that describe the packing density of
uniform spheres. For example, if the arrays are centred on a square grid
system there is more free space than if they are arranged as an hexagonal
array. Was this not the Kepler Conjecture, a notion that is difficult to
prove which has an answer known to every Green Grocer who displays Apples
and Oranges.
It should also be possible to calculate the diameter of balls that will fit
tangentially within the spaces created by open or close packing the larger
spheres.
By the time you get the third smaller spheres and insert some dominoes there
would be insufficient space for water. So motion would not be an issue.

Perhaps it is time to examine and image real plastic systems rather than
consider hypothetical constructs.
Best regards,

Ivor

____________________________________________________________________________
__
Send postings to clayart@lsv.ceramics.org

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settings from http://www.ceramics.org/clayart/

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### Leigh Whitaker on mon 2 apr 07

In a message dated 4/2/2007 8:41:21 A.M. Eastern Daylight Time,
wjsvt@SOVER.NET writes:

Ivor:
I believe you are on to something here.
Perhaps an examination (under a microscope of a power I can only dream of
) of the same clay body, in a short state and in a plastic state would
yield some valuable clues as to the nature of the truth in what we are all
saying. We can easily get to the bottom of this. Once short and plastic has
been examined, then a sample put aside for aging, and a comparison made as
well. Examine all the variables, decide what is happening.

Does anyone have an electron microscope hanging around?
Best,
Wayne Seidl

Ha ha, I did before I quit my job, but you might could hire one out, or
convince a student or technician to give you a freebie. The hospital/research
facility I used to work at had one that was extremely underused. They had a
tech who liked looking at unusual things with the scope. One thing to consider
with this idea... There are two types of EM: Scanning EM (SEM), and
Transmission EM (TEM). SEM looks at surfaces of materials. TEM looks at a very,
very, very thin slice through. In both methods the tiny little chunk or slice
of clay you would be looking at would likely dry out as the test was being
conducted. Would this affect the result?

I've only done EM on biological samples, so I don't know what kind of tricks
materials scientists have for looking at crystals and things. For
biological we'd have to fix them in some nasty chemicals (formaldehyde, osmium
tetroxide, etc..), and go through a laborious protocol to embed them in epoxy
resins. That's for TEM. SEM is much easier you either just look at it if it's
pretty sturdy, or if it's more fragile, put it in a chamber to coat it with gold
particles, then look at it.

How small are clay particles? Just curious.

Leigh

************************************** See what's free at http://www.aol.com.

### Leigh Whitaker on mon 2 apr 07

Here's a neat paper I just found

_http://www.clays.org/journal/archive/volume%203/3-1-1.pdf_
(http://www.clays.org/journal/archive/volume%203/3-1-1.pdf)

I have no idea how old that paper is, but it's the first one I found that I
could pull up as a pdf. I guess there are good ways of looking at clay
structure with EM, involving coating the clay with some sort of polymer or
something, and making a replica of either the surface or a cleavage plane. It would
certainly be interesting to see differences in aged clay versus not-aged.

Leigh

************************************** See what's free at http://www.aol.com.

### Matthew Katz on mon 2 apr 07

Hi,
Well, I have officially been left in the dust in this conversation. I will
admit to knowing about the methodology of packing spheres. But I just wanted
to say the the "Room of balls" as a metaphor has some major weaknesses. In
that the particles that we are speaking of are severally un-spherical, so I
am not sure how well those calculations would apply. Also the variations in
SSA (Specific Surface Area), Morphology, and PSD vary widely form clay to
clay, so we have found that the only effective way to determine PE is to
test each clay.
Wayne, I'm not quite sure exactly what you mean by 'Plastic" and "Short" but
it sounds to me like you are talking about different moisture contents. We
have found two thing. GPD is completely independent of moisture content. The
Variation of 3-5% for soft clay (23-24%) to hard (19-20%) are not enough to
effect GPD. And also what I would call short is a composistion issue, so
that it is impossible to have "short" and plastic in the same body. That
said this may be a definition question for me.
Best,
Matt

On 4/2/07, WJ Seidl wrote:
>
> Ivor:
> I believe you are on to something here.
> Perhaps an examination (under a microscope of a power I can only dream of
> ) of the same clay body, in a short state and in a plastic state would
> yield some valuable clues as to the nature of the truth in what we are all
> saying. We can easily get to the bottom of this. Once short and plastic
> has
> been examined, then a sample put aside for aging, and a comparison made as
> well. Examine all the variables, decide what is happening.
>
> Does anyone have an electron microscope hanging around?
> Best,
> Wayne Seidl
>
> -----Original Message-----
> From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Ivor and
> Olive
> Lewis
> Sent: Monday, April 02, 2007 3:15 AM
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: - a packing density question
>
> Are there not mathematical rules that describe the packing density of
> uniform spheres. For example, if the arrays are centred on a square grid
> system there is more free space than if they are arranged as an hexagonal
> array. Was this not the Kepler Conjecture, a notion that is difficult to
> prove which has an answer known to every Green Grocer who displays Apples
> and Oranges.
> It should also be possible to calculate the diameter of balls that will
> fit
> tangentially within the spaces created by open or close packing the larger
> spheres.
> By the time you get the third smaller spheres and insert some dominoes
> there
> would be insufficient space for water. So motion would not be an issue.
>
> Perhaps it is time to examine and image real plastic systems rather than
> consider hypothetical constructs.
> Best regards,
>
> Ivor
>
>
> ____________________________________________________________________________
> __
> 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
>
>
> ______________________________________________________________________________
> 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
>

--
Matthew Katz
Alfred, NY

### Thomas Malone on mon 2 apr 07

Hello Ivor. You re right there are mathematical rules that describe the
packing density of uniform spheres. A useful introduction of a simple
system can be found in =93Pottery Science by Allen Dinsdale.=94 The problems=
,
as you may have guessed, are applying models of simple systems to real
systems. Not only does the complexity of calculations increase
exponentially with each additional size but, very importantly, raw material
particles used in pottery are neither uniformly sized nor shaped. This can
be seen from (1) Particle size analysis. The results show a range of sizes,
and their calculations are based on the assumptions of spheres: known as
Equivalent Spherical Diameter. This is a huge simplification, but the only
way measurement techniques can be used. (2) Particle morphology. The
idealised shape of kaolinite particles are hexagons, but SEM examination
will show these are rarely perfect. Additionally there is a wide range of
aspect ratios. Non plastic particles are even more complex, being
incredibly irregular in shape.

Mathematical modelling of the raw material particles is, by a wide margin,
just too complicated!

### WJ Seidl on mon 2 apr 07

Matt:
I'm sure that others will offer their own view on the subject. There are as
many opinions here as there are people, and that is a good thing.

For me, the most basic test (definition) of "plastic" or "short" is on the
clay body itself.
A "short" body will reveal itself rather quickly with this method:
Roll a coil of clay about the thickness of a pencil or better.
Attempt to wrap that coil around your finger. Short clays will crack as you
wrap the clay. "Plastic" clays will not, or will crack significantly less.
Therefore, _depending_on_your_process_ (emphasis mine) a clay body can be
either short or plastic.
It's all in how your process works, what you use the particular body for.
Throwing, sculpting, hand building...all these processes require different
things from the clay. To further confound matters, with different processes,
the same body can be both. A clay a hand builder finds too plastic might be
too short for a thrower or sculptor, etc.
Short and plastic are _sometimes_ a result of moisture or lack of, sometimes
a result of body composition, and (most often, from my experience) a
combination of the two. Conditions/variables affecting "short" and
"plastic" are well known, and have been pointed out to us time after time on
the list by folks who make their living "knowing", and who have been kind
enough to try to help us. Whole chapters of books have been written to
explain the differences and why they happen.
For potters, it might be best to say that a determination of short and
plastic depends on the process for which the clay will be used and let it go
at that. There is no "reference point" from which to make a standard
determination that I know of. More's the pity.

Again, I caution everyone reading this not to confuse apples with
grapefruit.
As Matt mentions, GPD (green packing density) is independent of moisture
content. I will accept that from him as "fact", since I have not done the
research. Matt has. And it makes sense. Water will not cause particles to
pack more tightly, (but might aid in the movement of those particles.)
GPD has little if anything to do with short, plastic, aging, etc. It is
what it is. No more cantaloupes, ok?

Best,
Wayne Seidl

-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Matthew Katz
Sent: Monday, April 02, 2007 9:28 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: - a packing density question

Hi,
Well, I have officially been left in the dust in this conversation. I will
admit to knowing about the methodology of packing spheres. But I just wanted
to say the the "Room of balls" as a metaphor has some major weaknesses. In
that the particles that we are speaking of are severally un-spherical, so I
am not sure how well those calculations would apply. Also the variations in
SSA (Specific Surface Area), Morphology, and PSD vary widely form clay to
clay, so we have found that the only effective way to determine PE is to
test each clay.
Wayne, I'm not quite sure exactly what you mean by 'Plastic" and "Short" but
it sounds to me like you are talking about different moisture contents. We
have found two thing. GPD is completely independent of moisture content. The
Variation of 3-5% for soft clay (23-24%) to hard (19-20%) are not enough to
effect GPD. And also what I would call short is a composistion issue, so
that it is impossible to have "short" and plastic in the same body. That
said this may be a definition question for me.
Best,
Matt

On 4/2/07, WJ Seidl wrote:
>
> Ivor:
> I believe you are on to something here.
> Perhaps an examination (under a microscope of a power I can only dream of
> ) of the same clay body, in a short state and in a plastic state would
> yield some valuable clues as to the nature of the truth in what we are all
> saying. We can easily get to the bottom of this. Once short and plastic
> has
> been examined, then a sample put aside for aging, and a comparison made as
> well. Examine all the variables, decide what is happening.
>
> Does anyone have an electron microscope hanging around?
> Best,
> Wayne Seidl
>
> -----Original Message-----
> From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Ivor and
> Olive
> Lewis
> Sent: Monday, April 02, 2007 3:15 AM
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: - a packing density question
>
> Are there not mathematical rules that describe the packing density of
> uniform spheres. For example, if the arrays are centred on a square grid
> system there is more free space than if they are arranged as an hexagonal
> array. Was this not the Kepler Conjecture, a notion that is difficult to
> prove which has an answer known to every Green Grocer who displays Apples
> and Oranges.
> It should also be possible to calculate the diameter of balls that will
> fit
> tangentially within the spaces created by open or close packing the larger
> spheres.
> By the time you get the third smaller spheres and insert some dominoes
> there
> would be insufficient space for water. So motion would not be an issue.
>
> Perhaps it is time to examine and image real plastic systems rather than
> consider hypothetical constructs.
> Best regards,
>
> Ivor
>
>
>
____________________________________________________________________________
> __
> 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
>
>
>
____________________________________________________________________________
__
> 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
>

--
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

### Lynne and Bruce Girrell on mon 2 apr 07

>There are two types of EM: Scanning EM (SEM), and
>Transmission EM (TEM). SEM looks at surfaces of materials. TEM looks at
>a very,
>very, very thin slice through. In both methods the tiny little chunk or
>slice
>of clay you would be looking at would likely dry out as the test was being
>conducted. Would this affect the result?

There are also "environmental" SEMs that can tolerate samples containing
moisture. The sample is still under vacuum and will dry out as a result, but
at a much slower rate than with traditional SEMs.

The drying issue is a serious one, to which any potter who has watched their
pots crack can attest. There is a technique, however, called "critical point
drying" that allows for the drying of a substance without the shape changes
normally encountered during drying. Normal critical point drying involves
the exchange of water within the sample with an intermediate fluid such as
acetone. Because of the horridly low permeability of clay and the
possibility of disturbing the sample during flushing of the water, I don't
think that this would work well for clay samples.

On a list similar to Clayart but dedicated to microscopy, I asked if
critical point drying could be accomplished without the intermediate fluid
and suggested a way in which it might be accomplished. It requires high
pressure, but I have access to oilfield piping that can withstand the
required pressure. Those on the list said that it sounded as though it could
work and encouraged me to give it a go. In fact they wanted me to write an
article if it worked. Haven't tried it yet, though.

>How small are clay particles? Just curious.

They are right at the limits of the resolution of optical microscopes.
Though you could see them, they would just be specks. An SEM is just about a
requirement.

Bruce Girrell

_________________________________________________________________
Mortgage refinance is hot 1) Rates near 30-yr lows 2) Good credit get
intro-rate 4.625%*

### Matthew Katz on mon 2 apr 07

Does anyone know if I can I embed photos on this list? I could show a few.
20,000x will show a few hundred/thousand particles. At that magnification a
human hair would be two feet wide and a clay particle would still be only
1/6 to 1/2 an inch

On 4/2/07, Lynne and Bruce Girrell wrote:
>
> >There are two types of EM: Scanning EM (SEM), and
> >Transmission EM (TEM). SEM looks at surfaces of materials. TEM looks
> at
> >a very,
> >very, very thin slice through. In both methods the tiny little chunk or
> >slice
> >of clay you would be looking at would likely dry out as the test was
> being
> >conducted. Would this affect the result?
>
> There are also "environmental" SEMs that can tolerate samples containing
> moisture. The sample is still under vacuum and will dry out as a result,
> but
> at a much slower rate than with traditional SEMs.
>
> The drying issue is a serious one, to which any potter who has watched
> their
> pots crack can attest. There is a technique, however, called "critical
> point
> drying" that allows for the drying of a substance without the shape
> changes
> normally encountered during drying. Normal critical point drying involves
> the exchange of water within the sample with an intermediate fluid such as
> acetone. Because of the horridly low permeability of clay and the
> possibility of disturbing the sample during flushing of the water, I don't
> think that this would work well for clay samples.
>
> On a list similar to Clayart but dedicated to microscopy, I asked if
> critical point drying could be accomplished without the intermediate fluid
> and suggested a way in which it might be accomplished. It requires high
> pressure, but I have access to oilfield piping that can withstand the
> required pressure. Those on the list said that it sounded as though it
> could
> work and encouraged me to give it a go. In fact they wanted me to write an
> article if it worked. Haven't tried it yet, though.
>
> >How small are clay particles? Just curious.
>
> They are right at the limits of the resolution of optical microscopes.
> Though you could see them, they would just be specks. An SEM is just about
> a
> requirement.
>
> Bruce Girrell
>
> _________________________________________________________________
> Mortgage refinance is hot 1) Rates near 30-yr lows 2) Good credit get
> intro-rate 4.625%*
>
>
>
> ______________________________________________________________________________
> 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
>

--
Matthew Katz
Alfred, NY

### Matthew Katz on mon 2 apr 07

Mel is going to put one up on the site for me. Sorry about the watermarking,
we don't want anyone else to claim it as their own, which is too easy on
these internets.
You get the idea though.
Enjoy,
Matt

On 4/2/07, Matthew Katz wrote:
>
> Does anyone know if I can I embed photos on this list? I could show a few.
>
> 20,000x will show a few hundred/thousand particles. At that magnification
> a human hair would be two feet wide and a clay particle would still be only
> 1/6 to 1/2 an inch
>
> On 4/2/07, Lynne and Bruce Girrell wrote:
> >
> > >There are two types of EM: Scanning EM (SEM), and
> > >Transmission EM (TEM). SEM looks at surfaces of materials. TEM looks
> > at
> > >a very,
> > >very, very thin slice through. In both methods the tiny little chunk
> > or
> > >slice
> > >of clay you would be looking at would likely dry out as the test was
> > being
> > >conducted. Would this affect the result?
> >
> > There are also "environmental" SEMs that can tolerate samples containing
> >
> > moisture. The sample is still under vacuum and will dry out as a result,
> > but
> > at a much slower rate than with traditional SEMs.
> >
> > The drying issue is a serious one, to which any potter who has watched
> > their
> > pots crack can attest. There is a technique, however, called "critical
> > point
> > drying" that allows for the drying of a substance without the shape
> > changes
> > normally encountered during drying. Normal critical point drying
> > involves
> > the exchange of water within the sample with an intermediate fluid such
> > as
> > acetone. Because of the horridly low permeability of clay and the
> > possibility of disturbing the sample during flushing of the water, I
> > don't
> > think that this would work well for clay samples.
> >
> > On a list similar to Clayart but dedicated to microscopy, I asked if
> > critical point drying could be accomplished without the intermediate
> > fluid
> > and suggested a way in which it might be accomplished. It requires high
> > pressure, but I have access to oilfield piping that can withstand the
> > required pressure. Those on the list said that it sounded as though it
> > could
> > work and encouraged me to give it a go. In fact they wanted me to write
> > an
> > article if it worked. Haven't tried it yet, though.
> >
> > >How small are clay particles? Just curious.
> >
> > They are right at the limits of the resolution of optical microscopes.
> > Though you could see them, they would just be specks. An SEM is just
> > requirement.
> >
> > Bruce Girrell
> >
> > _________________________________________________________________
> > Mortgage refinance is hot 1) Rates near 30-yr lows 2) Good credit get
> > intro-rate 4.625%*
> >
> >
> > ______________________________________________________________________________
> >
> > 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
> >
>
>
>
> --
> Matthew Katz
> Alfred, NY

--
Matthew Katz
Alfred, NY