iandol on wed 8 oct 03
Dear Ron Roy,
You are joining the others and galloping ahead. Slow down friend, slow =
down.
What I am trying to get at has nothing to do with firing the clay. It is =
about getting the best qualities we can so that it gives the best degree =
of plastic strength possible. I agree that the common practice of =
bending a coil of stuff around one's little finger gives us some idea of =
its usefulness: short, good or tacky. But that is like sharing out =
marbles by saying "One, Two, Many" not a very good scale to judge =
plastic potential.
You ask for an analysis. Rado gives us C1, a China Clay: SiO2-48.60, =
TiO2-0.05, Al2O3-36.80, Fe2O3-0.50, CaO-0.16, Mg)0.25, K2O-1.18, =
Na2O-0.26, Loss on Ignition 12.20. Now tell me, what do you infer about =
the plasticity from this information? Ignore its shrinkage. Ignore its =
firing characteristics. All that is needed is some appraisal about the =
influence of the minor metallic elements on the degree of plasticity. My =
suggestion is that with sufficient water to get a plastic substance the =
clay would have poor plastic strength and be "Flabby". What would you =
say?
Best regards,
Ivor Lewis. Redhill, South Australia
iandol on wed 8 oct 03
Dear Friend,
You are racing ahead again ! Yes, I believe you are right to suggest =
that the surface of each clay crystal has the ability to adsorb myriads =
of Ions. But I think it is an assumption to classify them as Acid or =
Alkali. (I have deep reservations about using these terms to qualify =
material classifications in Ceramics) Perhaps we should think of them as =
either Metallic Ions or Non Metallic Ions. This would be more in line =
with the teachings of Lawrence and West on the one hand and Rado on the =
other. Once people talk to me about Acid and Alkali I get visions of =
exploding gas which evolves, for example, when Hydrochloric acid =
(Popular with ceramists for "Killing" the deflocculated state and =
restoring flocculation in glazes) is poured onto Zinc granules in a test =
tube.
Your observations about the influence of Yeast could set up some =
interesting theories.
As to the effects of "Acid" on Kaolinite, this is something I do not =
know.
I seek enlightenmment in the face of contrasting and opposing theories. =
I seek knowledge. My question asks about the effects of residual =
fractions of Alkali, Alkali Earth or other higher valency metallic =
elements and their influence on the relationship between Kaolinite or =
its derivatives, such as Ball Clay and Water. Rado expresses these as =
fractions of Na, K or Ca Felspar. Suppliers, Clay and Glaze experts =
express them as Molecular Oxides. Both opinions seem to incorporate a =
reasonable degree of assumption and conjecture.
So you ask questions for which I have no answer.
In the face of current opinions, I feel my inquisitiveness is justified =
and I sense you have a similar attitude.
Best regards, and thank you for your interest and comments.
Ivor Lewis. Redhill, South Australia
Ron Roy on fri 10 oct 03
Hi Ivor,
As I have stated - I get no information from the chemical analysis about
the plasticity
It may be flabby and have poor plastic strength - but not because of the
minor fluxes - you can find them in thousands of other clays - which have
good working characteristics.
When primary clays are transported from the original site they gather
carbonaceous materials, iron and are particle sorted.
It is not as simple as that but those are your clues.
RR
>Dear Ron Roy,
>You ask for an analysis. Rado gives us C1, a China Clay: SiO2-48.60,
>TiO2-0.05, Al2O3-36.80, Fe2O3-0.50, CaO-0.16, Mg)0.25, K2O-1.18,
>Na2O-0.26, Loss on Ignition 12.20. Now tell me, what do you infer about
>the plasticity from this information? Ignore its shrinkage. Ignore its
>firing characteristics. All that is needed is some appraisal about the
>influence of the minor metallic elements on the degree of plasticity. My
>suggestion is that with sufficient water to get a plastic substance the
>clay would have poor plastic strength and be "Flabby". What would you say?
>
>Best regards,
>Ivor Lewis. Redhill, South Australia
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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