ivor and olive lewis on fri 13 jul 12
I have had a break through in my quest for knowledge which discriminates
between the fluxing abilities the Alkali Metal oxides (Li, Na, K.) and the
alkali Earth Oxides (Mg, Ca, Sr, Ba plus Zn and Al).
Hypothetically, I chose Electronic Charge and Ionic Radius as the governing
factors of this physical factor,
Theoretically, the smaller the Ionic radius and the greater the electronic
charge on the fluxing ion the greater the viscosity of the melt. Conversely=
,
the larger the ionic radius and the smaller the electronic charge the
greater the fluidity of the melt.
Calculating these relationships leads to the following list which suggests
the degree of viscosity increases from left to right.
K2O>Na2O>BaO>SrO>Li2O>CaO>ZnO>MgO>Al2O3
Of concern and unclear is the potential for Synergistic or enhancement of
fluidity, or the inhibition of these qualities as the variety or quantity o=
f
fluxing ions is increased. Another question arising relates to the effects
on viscosity of the remaining vitreous melt when compounds crystallise from
the melt. It would seem that reducing the content of the glaze of specific
compounds to cause Opacity, Mattness or crystallisation could lead to
increasing fluidity of the residue causing draining from the face of vase
forms or pooling in bowls.
There are other questions relating to the effects of differing maturity
temperatures
Regards,
Ivor Lewis,
REDHILL,
South Australia
Hank Murrow on fri 13 jul 12
Say Ivor;
I would suggest that you peruse Michael Cardew's "Pioneer Pottery" on =3D
page 310, Appendix 13. Common elements ocurring in Pottery. There he =3D
discusses the bonds which must be broken to effect a melt, and presents =3D
an elegant formulation regarding Ionic Potential, the valency divided by =
=3D
the ionic radius, which measures the strength of the cation-oxygen bond.
Following Cardew's model based upon Ionic Potential may suggest some =3D
alteration to your list of greater to lesser fluxing ions.
I have had the chart from this appendix on the wall of my studio ever =3D
since his lectures at the U of Oregon in Fall of '67.
David Stannard went so far as to make a brass model of each of the =3D
ceramic ions from Cardew's table ranged along the bar according to =3D
valence and Ionic Potental____ which helped him (and me, since I have =3D
one too) to visualize how the common ions are likely to interact with =3D
each other in a glaze.
Sometimes when I present workshops, I share the model and suggest =3D
experiments to demonstrate its effectiveness in predicting melts. It =3D
takes a keen mind interested in process to make good use of it, but for =3D
such a mind it is a way through the confusing world of ceramic melts. =3D
That world for me is chaotic enough that I am willing to put in the time =
=3D
each firing to test notions every chance I get. After all, how many =3D
firings can one expect to do in a potter's career?
Cheers, Hank in Eugene, OR(up over :)
On Jul 13, 2012, at 12:39 AM, ivor and olive lewis wrote:
> I have had a break through in my quest for knowledge which =3D
discriminates
> between the fluxing abilities the Alkali Metal oxides (Li, Na, K.) and =
=3D
the
> alkali Earth Oxides (Mg, Ca, Sr, Ba plus Zn and Al).
> Hypothetically, I chose Electronic Charge and Ionic Radius as the =3D
governing
> factors of this physical factor,
> Theoretically, the smaller the Ionic radius and the greater the =3D
electronic
> charge on the fluxing ion the greater the viscosity of the melt. =3D
Conversely,
> the larger the ionic radius and the smaller the electronic charge the
> greater the fluidity of the melt.
> Calculating these relationships leads to the following list which =3D
suggests
> the degree of viscosity increases from left to right.
>=3D20
> K2O>Na2O>BaO>SrO>Li2O>CaO>ZnO>MgO>Al2O3
>=3D20
> Of concern and unclear is the potential for Synergistic or enhancement =
=3D
of
> fluidity, or the inhibition of these qualities as the variety or =3D
quantity of
> fluxing ions is increased. Another question arising relates to the =3D
effects
> on viscosity of the remaining vitreous melt when compounds crystallise =
=3D
from
> the melt. It would seem that reducing the content of the glaze of =3D
specific
> compounds to cause Opacity, Mattness or crystallisation could lead to
> increasing fluidity of the residue causing draining from the face of =3D
vase
> forms or pooling in bowls.
> There are other questions relating to the effects of differing =3D
maturity
> temperatures
>=3D20
> Regards,
> Ivor Lewis,
> REDHILL,
> South Australia
>=3D20
Hank Murrow on fri 13 jul 12
Say Ivor;
David Stannard went so far as to make a brass model of each of the =3D
ceramic ions from Cardew's table ranged along the bar according to =3D
valence and Ionic Potental____ which helped him (and me, since I have =3D
one too) to visualize how the common ions are likely to interact with =3D
each other in a glaze.
Forgot to include a pic of the Ionic Radius 'bar'.
Hank
Oxygen at near end.
Oxygen at the far end, cations(one missing ion) in order according to =3D
I.P. beginning at the near end.=3D
ivor and olive lewis on sat 14 jul 12
Listening Hank,
I have great faith in Michael Cardew. But the if you think carefully you ar=
e
faced with a dilemma. Are you imagining in one or three dimensions ?
In my model cations are presumed to be spherical so the net attractive forc=
e
of the protons must be normal to the surface of the sphere. Calculate the
surface area of each, divide by the valency then find the inverse value and
you have the net positive charge per square angstrom ( I used Picometres )
You have an elegant model.
Cheers,
Ivor
----- Original Message -----
From: "Hank Murrow"
To: "ivor and olive lewis" ; "CLAYART LIST"
Sent: Saturday, July 14, 2012 4:19 AM
Subject: Re: Viscosity of Glaze
Say Ivor;
I would suggest that you peruse Michael Cardew's "Pioneer Pottery" on page
310, Appendix 13. Common elements ocurring in Pottery. There he discusses
the bonds which must be broken to effect a melt, and presents an elegant
formulation regarding Ionic Potential, the valency divided by the ionic
radius, which measures the strength of the cation-oxygen bond.
Following Cardew's model based upon Ionic Potential may suggest some
alteration to your list of greater to lesser fluxing ions.
I have had the chart from this appendix on the wall of my studio ever since
his lectures at the U of Oregon in Fall of '67.
David Stannard went so far as to make a brass model of each of the ceramic
ions from Cardew's table ranged along the bar according to valence and Ioni=
c
Potental____ which helped him (and me, since I have one too) to visualize
how the common ions are likely to interact with each other in a glaze.
Sometimes when I present workshops, I share the model and suggest
experiments to demonstrate its effectiveness in predicting melts. It takes =
a
keen mind interested in process to make good use of it, but for such a mind
it is a way through the confusing world of ceramic melts. That world for me
is chaotic enough that I am willing to put in the time each firing to test
notions every chance I get. After all, how many firings can one expect to d=
o
in a potter's career?
Cheers, Hank in Eugene, OR(up over :)
On Jul 13, 2012, at 12:39 AM, ivor and olive lewis wrote:
> I have had a break through in my quest for knowledge which discriminates
> between the fluxing abilities the Alkali Metal oxides (Li, Na, K.) and th=
e
> alkali Earth Oxides (Mg, Ca, Sr, Ba plus Zn and Al).
> Hypothetically, I chose Electronic Charge and Ionic Radius as the
> governing
> factors of this physical factor,
> Theoretically, the smaller the Ionic radius and the greater the electroni=
c
> charge on the fluxing ion the greater the viscosity of the melt.
> Conversely,
> the larger the ionic radius and the smaller the electronic charge the
> greater the fluidity of the melt.
> Calculating these relationships leads to the following list which suggest=
s
> the degree of viscosity increases from left to right.
>
> K2O>Na2O>BaO>SrO>Li2O>CaO>ZnO>MgO>Al2O3
>
> Of concern and unclear is the potential for Synergistic or enhancement of
> fluidity, or the inhibition of these qualities as the variety or quantity
> of
> fluxing ions is increased. Another question arising relates to the effect=
s
> on viscosity of the remaining vitreous melt when compounds crystallise
> from
> the melt. It would seem that reducing the content of the glaze of specifi=
c
> compounds to cause Opacity, Mattness or crystallisation could lead to
> increasing fluidity of the residue causing draining from the face of vase
> forms or pooling in bowls.
> There are other questions relating to the effects of differing maturity
> temperatures
>
> Regards,
> Ivor Lewis,
> REDHILL,
> South Australia
>
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