I.Lewis on sun 16 jan 00
------------------
Porcelain. 1 Materials. A brief and simple overview.
If it is accepted that Translucency is the Hallmark of Porcelain then it =
becomes
necessary to investigate the causes of this phenomenon so that it can be
enhanced by our control over selection of materials and firing cycles.
Understanding Translucency comes from knowledge of raw materials, how they
behave when we heated them together and how Light behaves when it impinges =
on
the surface of Porcelain.
Of books published devoted to Porcelain, that by Peter Lane, STUDIO =
PORCELAIN,
gives a comprehensive view and illustrates the quality of translucency.
Materials. Three materials are essential=3B Clay, Flux and Silica.
Clay provides structural strength.
Flux provides a fluid environment for the chemical reactions.
Silica ensures that the material will be vitreous, that is, Glass like.
This information is corroborated by Frank Hamer and James Chappell.
Materials are chosen for their freedom from compounds which cause
discolouration. Clays which meet this standard usually have poor plasticity.
Plasticity is enhanced by adding Ball Clay or a mineral plasticiser such as
Bentonite
Clay is usually a white firing Kaolin. Flux is usually some form of Felspar.
Silica is derived from Quartz minerals.
Contaminants include Iron or Iron bearing minerals and to a lesser degree
Manganese minerals and Titanium minerals which were part of the original =
rocks
from which the Kaolin was formed. Whiteness comes from the reflectivity of =
the
principle materials after they have been fired, not from their body colour. =
I
have Gem Grade Quartz and Silica which are transparent and water clear. They
looks white when powdered. I have gem grade Felspar which is transparent. Do=
not
be deceived by appearances.
References.
Chappell, James. The Potter=92s Complete Book of Clay and Glazes. Watson =
Guptill
Publications. 1977. New York.
Hamer, Frank. The Potter=92s Dictionary of Materials and Techniques. Pitman
Publishing. London. 1975.
Lane, Peter. Studio Porcelain. Pitman House Limited. London. 1980.
Next excerpt will be about the changes to the materials and the qualities of=
the
new materials which form.
Ivor Lewis. Inquisitive as ever.
Earl Brunner on mon 17 jan 00
------------------
Lets stipulate that Translucency is =2Aa=2A hallmark of =2Asome=2A =
porcelain.
Personally I wouldn't really want or desire my commode to be translucent.
I.Lewis wrote:
=3E ----------------------------Original message----------------------------
=3E ------------------
=3E Porcelain. 1 Materials. A brief and simple overview.
=3E
=3E If it is accepted that Translucency is the Hallmark of Porcelain then it
becomes
=3E necessary to investigate the causes of this phenomenon so that it can be
=3E enhanced by our control over selection of materials and firing cycles.
=3E Understanding Translucency comes from knowledge of raw materials, how =
they
=3E behave when we heated them together and how Light behaves when it =
impinges on
=3E the surface of Porcelain.
=3E
=3E Of books published devoted to Porcelain, that by Peter Lane, STUDIO =
PORCELAIN,
=3E gives a comprehensive view and illustrates the quality of translucency.
=3E
=3E Materials. Three materials are essential=3B Clay, Flux and Silica.
=3E
=3E Clay provides structural strength.
=3E
=3E Flux provides a fluid environment for the chemical reactions.
=3E
=3E Silica ensures that the material will be vitreous, that is, Glass like.
=3E
=3E This information is corroborated by Frank Hamer and James Chappell.
=3E
=3E Materials are chosen for their freedom from compounds which cause
=3E discolouration. Clays which meet this standard usually have poor =
plasticity.
=3E Plasticity is enhanced by adding Ball Clay or a mineral plasticiser such=
as
=3E Bentonite
=3E
=3E Clay is usually a white firing Kaolin. Flux is usually some form of =
Felspar.
=3E Silica is derived from Quartz minerals.
=3E
=3E Contaminants include Iron or Iron bearing minerals and to a lesser =
degree
=3E Manganese minerals and Titanium minerals which were part of the original=
rocks
=3E from which the Kaolin was formed. Whiteness comes from the reflectivity =
of the
=3E principle materials after they have been fired, not from their body =
colour. I
=3E have Gem Grade Quartz and Silica which are transparent and water clear. =
They
=3E looks white when powdered. I have gem grade Felspar which is =
transparent. Do
not
=3E be deceived by appearances.
=3E
=3E References.
=3E
=3E Chappell, James. The Potter=92s Complete Book of Clay and Glazes. Watson=
Guptill
=3E Publications. 1977. New York.
=3E
=3E Hamer, Frank. The Potter=92s Dictionary of Materials and Techniques. =
Pitman
=3E Publishing. London. 1975.
=3E
=3E Lane, Peter. Studio Porcelain. Pitman House Limited. London. 1980.
=3E
=3E Next excerpt will be about the changes to the materials and the =
qualities of
the
=3E new materials which form.
=3E
=3E Ivor Lewis. Inquisitive as ever.
--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec=40anv.net
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