Cobus Potgieter on tue 20 jun 00
Before sanitary ware was made from vitrious china, it was made from =
fireclay. The castings (solid casting) were sometimes up to 25mm (1 =
inch) thick. I can not find any information about the casting of such =
thick objects. Can anyone help me with more information? (body =
composition / casting time)
Thanks,
Cobus Potgieter.
NAMIBIA CERAMICS Tel: +264-61-264526
PO Box 6742 Fax: +264-61-261590
Ausspannplatz
Windhoek
NAMIBIA
http://www.orusovo.com/namceram
namceram@orusovo.com
Des Howard on thu 22 jun 00
Cobus
Many years ago I worked in a ceramics factory that had only recently
changed the sanitary ware (toilet bowls, cisterns, urinals, sinks) body to
high density vitreous china fired in an oil fuelled tunnel kiln.
Formerly they had used a coarse body, probably a slightly finer version of
their high firing sewer pipe body which was salt glazed in coal fuelled round kilns.
The old sanitary ware was slab made, laid up in wooden moulds,
component parts luted, the ware was sprayed with a white slip,
then sprayed with a clear glaze then fired in the non salting coal kilns.
Des
Cobus Potgieter wrote:
> Before sanitary ware was made from vitrious china, it was made from fireclay. The castings (solid casting) were sometimes up to 25mm (1 inch) thick. I can not find any information about the casting of such thick objects. Can anyone help me with more information? (body composition / casting time)
> Thanks,
> Cobus Potgieter.
--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
Janet Kaiser on fri 23 jun 00
Greetings Cobus!
I cannot help you, but have taken the following from
Chapter XIII Refractories, in "Pottery and Ceramics" by
Ernst Rosenthal, 1949.
Page 165: FIRECLAY WARE
The composition of fireclays varies considerably as the
following table shows:
Content Per cent
Silica..................46 to 63
Alumina.............32 to 45
Iron.....................0.7 to 2.5
Lime..................0.1 to 0.6
Magnesia........traces to 0.5
Alkali................traces to 1.6
The influences which the various impurities impart to a
clay have been described previously in this book.
Shaping of Fireclay Goods:
Fire-brick standards and special shapes are
manufactured according to circumstances:
1. By hand moulding from plastic mixture
2. By machine pressing from a coarse damp dust.
3. By extrusion through dies of a plastic nature
4. By tamping of damp dust or plastic clay by rammers
into strongly-made moulds.
5. By casting
These shaping processes yield fireclay refractories for
boiler furnaces, blast furnaces, gas retort settings,
lime kilns, cement kilns and metallurgical furnaces for
melting, re-heating and heat treatment of iron, steel
and non-ferrous metals.
Fireclay hollow-ware includes fireclay crucibles, large
and small, for melting metals, enamels and glass;
fireclay tubes and other small furnace chambers and a
multitude of specialised shapes for external heating by
coke ,gas, oil and resistance winding. Methods employed
for the manufacture of refractory hollow-ware include
spinning, pressing, extrusion, tamping and slip
casting. Slip casting used to be confined to porcelain
and earthenware manufacture. It is, however, now being
increasingly used in the manufacture of refractories
owing to the fact that in liquid form the various
ingredients can be very thoroughly mixed.
Burning of Fireclay Goods:
The firing of fireclay goods is done in kilns of
various sizes and shapes - down-draught intermittent
ovens, continuous chamber kilns, tunnel kilns and other
types. The down-draught intermittent oven is the oldest
bust still the most widely used type of kiln for firing
refractories, though continuos chamber ovens and tunnel
kilns are used considerably where the outputs are
large. The time required for firing fireclay goods
usually varies from five to ten days according to the
class of goods being burnt and the type of kiln in use.
The temperature to which the goods are burnt also
varies and may be between 1200 and 1400 deg. C.
Fireclay goods rich in alumina are in most cases fired
to 1400 deg. C. and even higher. The cooling process
usually takes from seven to ten days according to the
class of the kiln in use. Cooling has to be carried out
very carefully, particularly in the case of large
articles, to avoid cracking of the ware owing to sudden
reduction of temperature. The cooling process can
however be speeded up if sudden falls in temperature
are avoided and the curve in the cooling zone is a
straight line. The most economical type of kiln for
fireclay goods is a modern tunnel oven because it is
possible to regulate heat increases and rate of cooling
according to the job in hand.
**********
There is nothing more about method I*m afraid.
I personally have my doubts that fireclay would be
suitable for casting in a workshop or studio
situation... Casting slips have to be fine otherwise
the very course particles sink and the final body would
not be homogeneous. Just my opinion!
Hope the above helps... What are you up to? A new
project?
Best wishes from wet and windy Wales where we have had
three summer days so far this year...
Janet Kaiser
The Chapel of Art . Capel Celfyddyd
HOME OF THE INTERNATIONAL POTTERS' PATH
Criccieth LL52 0EA, GB-Wales Tel: (01766) 523570
E-mail: postbox@the-coa.org.uk
WEBSITE: http://www.the-coa.org.uk
----- Original Message -----
From: Cobus Potgieter
To:
Sent: 21 June 2000 04:45
Subject: Slipcasting fireclay
Before sanitary ware was made from vitrious china, it
was made from fireclay. The castings (solid casting)
were sometimes up to 25mm (1 inch) thick. I can not
find any information about the casting of such thick
objects. Can anyone help me with more information?
(body composition / casting time)
Thanks,
Cobus Potgieter.
NAMIBIA
http://www.orusovo.com/namceram
namceram@orusovo.com
WHC228@AOL.COM on fri 23 jun 00
I don't understand why fireclay would be difficult to make into a casting
body. I would guess that some combination of flint feldspar ball clay and
fireclay could be put together and would stay in solution just fine. I use
velvacast in my porcelain because it has large particles and has better
casting properties because the water can move through it more easily than the
smaller particle clays.
Making up a slip from scratch is a long and involved process. There are a lot
of issues to deal with.
Viscosity
Flow
Gel rate
Beyond that there are the problems of
Expansion
fit Color
The list goes on and on.
You might try talking to one of the clay companies. They will probably be
able to give you somewhere to start. I have talked to several of the ball
clay companies in the past about casting slips and they were quite helpful
Bill
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