Robert Kittel on tue 27 may 97
Karl,
I work in a commercial pottery, (factory). We recently had to go to China to
have an item made. The proposal that came back listed the body as a dolomite
body. This is a new one on me, is there anything that you can tell me about
this?
Thanks
Bob
Karl P. Platt on wed 28 may 97
Dolomite, which adds MgO, when put into a clay body would tend to make
its firing range much shorter than a similar lime bearing body. Consider
Cordiorite, a high MgO composition, which is very refractory to a
certain point and then melts wholesale. Talc/ball clay ("hobby
porcelain") bodies show similar behavior.
As the body could contain a lot of glassy material, one would want to
test the ware for thermal shock resistance for applications requiring
it.
A QC check for consistency in processing would be a porosity check as
the body is very sensitive to heat treatment.
Ron Roy on fri 30 may 97
>----------------------------Original message----------------------------
>Dolomite, which adds MgO, when put into a clay body would tend to make
>its firing range much shorter than a similar lime bearing body. Consider
>Cordiorite, a high MgO composition, which is very refractory to a
>certain point and then melts wholesale. Talc/ball clay ("hobby
>porcelain") bodies show similar behavior.
>
>As the body could contain a lot of glassy material, one would want to
>test the ware for thermal shock resistance for applications requiring
>it.
Dolomite adds calcium as well with a similar effect on the melt. I would
caution against the use of MgO and CaO as body fluxes above cone 5. My
initial measurements indicate bodies which rely on fluxes other than Na2O
and K20 as body fluxes show increased levels of cristobalite. I expect Li2O
will have a similar effect (reduce cristobalite) when used in special low
expansion bodies.
I will eventually do more experiments in this area - stay tuned but it will
be a while. In the meantime, if you really must try using any of the mid
range fluxes in bodies, test for fit problems. Especially if you are making
anything which is to be used with heat.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
Studio: 416-752-7862.
Email ronroy@astral.magic.ca
Home page http://digitalfire.com/education/ronroy.htm
mel jacobson on sun 28 may 06
PLEASE let us know who you are.
i am not going to post anonymous
posts.
period.
from the farm
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