Zac Hould on tue 14 aug 12
Hello all,
This is my second post on the forum and hopin everyone's summer is windin=
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g
down well. Earlier this year, I took the Christopher/Anne Hogg bone china=
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recipe in various books and mixed up a 50lb or so batch. It was 50% bone
ash, 25% cornwall (cornish) stone and 25% super standard porcelain kaolin=
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. I
read it was a cone 10 rated body but did not survive. I had a small jar
completely melt flat and flow off the shelf and down to the next level of=
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the kiln. I am guessing it is a cone 8 porcelain.=3D20
My first question is if I were to stick with this recipe, due to simplici=
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ty
in materials, can I lower both the cornish and the bone ash and increase =
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the
kaolin to allow for a cone 10 firing? I would guess a revised formula wou=
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ld
be 45% bone ash, 20% cornish (cornwall) stone, 35 S.S.P. kaolin? Or do yo=
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u
thing bring the bone ash even lower, maybe 40% would be better since the
cornwall bring some silica to the mix?
I will mention that a teadust black on this formula when green completely=
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,
as if the crystals formed a complete layer on top of the body and no glos=
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s
formed. By the way, it was quite obvious how white this clay was. BLEACH
WHITE is a fair description. Very little workability and plasticity for t=
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he
wheel or wedging. Other funky thing was the grittyness in the slip while
throwing that was either from the bone ash or cornish stone. And after it=
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ages, the outside later goes that bright white and then cut it open and y=
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ou
see the moldy grey color of a dark buff or talc body. Interesting.
Second question, I am interested in mixing some small batches of halloysi=
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te
based porcelain for asymmetrical work. I read that it warps easily due to=
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the rolling and unrolling during wetting and drying factor in the materia=
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l.
I was hoping for a basic recipe with some fair or crude amount of workabi=
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lty
for the wheel. I will have no complaints of special materials if you have=
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a
complex or expensive recipe. I already have a fair amount in diverse
materials to use.
I am guessing some will tell me to take an existing cone 10 recipe and su=
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b
the kaolin for halloysite which I am fine with hearing but I am only aski=
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ng
due to curiousity if many recipes have floated around as a basic halloysi=
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te
body.=3D20
My best regards to all and happy potting!
Zac Hould
Los Angeles
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