Paul Borian on wed 26 mar 08
i have read that "machine mixed" clay will give a different absorption
percentage than the same clay mixed by hand - the difference would be that
the machine mixed clay is 1% less absorptive. The most recent tests i did
on my clay body showed less than 1%, and in some cases it was pretty close
to 0% and i got concerned but then i realized that not only is the clay
machine mixed but also run through a pugmill and produces especially dense
clay so i think i am alright with the numbers i am getting.
But i would like to know for sure just what "machine mixed" means in this
context - does it mean just clay that was produced in a mixer or does it
also imply that the clay was pugged before cut into test bars? Or if the
clay was pugged would that also affect the absorption values even more?
I know that some people do tests just by mixing the clay as a slip and
drying it out in small molds, and my pugged clay would be much more dense
than test bars made from slip.
Can anyone shed some light here?
thanks,
paul
Jeoung-Ah Kim on thu 27 mar 08
Dear Paul,
1. I wonder if you could give me the name of reference book you have read.
2. The term "machine mixed" must be clearified before one make an argument.
Regards,
Kim
Paul Borian wrote: i have read that "machine mixed" clay will give a different absorption
percentage than the same clay mixed by hand - the difference would be that
the machine mixed clay is 1% less absorptive. The most recent tests i did
on my clay body showed less than 1%, and in some cases it was pretty close
to 0% and i got concerned but then i realized that not only is the clay
machine mixed but also run through a pugmill and produces especially dense
clay so i think i am alright with the numbers i am getting.
But i would like to know for sure just what "machine mixed" means in this
context - does it mean just clay that was produced in a mixer or does it
also imply that the clay was pugged before cut into test bars? Or if the
clay was pugged would that also affect the absorption values even more?
I know that some people do tests just by mixing the clay as a slip and
drying it out in small molds, and my pugged clay would be much more dense
than test bars made from slip.
Can anyone shed some light here?
thanks,
paul
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Ron Roy on fri 28 mar 08
Hi Paul,
When I do preliminary testing of clays I add just enough water to make the
clay plastic enough to test and hand wedge. It doesn't seem to make any
difference how long it is hand wedged - the absorption of such tests is
typically 1% more than in clays that have been through a muller or Irex
mixer and deairing pugmill.
The type of mixer that is used will produce different results - many clay
manufactures just use a wad mill for premixing clay - I don't know what
that clay would test out for compared to a hand mixed sample.
Melting is influenced my particle size and packing - the finer the particle
size and the greater the packing - the more melting will happen.
Best to make the same clay and compare with the methods you will use to mix
your clay.
I don't know if wet mixing with excess water will give the same results as
a machine mixed clay - perhaps if they are both deaired.
It would be a good subject for an article if your inclined - if you need
others to duplicate some firings I'm sure there would be volunteers.
RR
>i have read that "machine mixed" clay will give a different absorption
>percentage than the same clay mixed by hand - the difference would be that
>the machine mixed clay is 1% less absorptive. The most recent tests i did
>on my clay body showed less than 1%, and in some cases it was pretty close
>to 0% and i got concerned but then i realized that not only is the clay
>machine mixed but also run through a pugmill and produces especially dense
>clay so i think i am alright with the numbers i am getting.
>But i would like to know for sure just what "machine mixed" means in this
>context - does it mean just clay that was produced in a mixer or does it
>also imply that the clay was pugged before cut into test bars? Or if the
>clay was pugged would that also affect the absorption values even more?
>I know that some people do tests just by mixing the clay as a slip and
>drying it out in small molds, and my pugged clay would be much more dense
>than test bars made from slip.
>Can anyone shed some light here?
>thanks,
>paul
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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