search  current discussion  categories  techniques - misc 

clay bodies in microwave

updated thu 23 feb 06

 

Bob Masta on mon 20 feb 06


Jon,
Regarding your wonderful test of different Laguna bodies
in the microwave, I'm wondering if there is some particular
component or balance of components in the bodies
that correlates with heat, besides (lack of) absorption. Like, do
the hotter bodies have more iron? I searched the Laguna
site and some Web databases but could't find analyses
for these bodies. Are they available? (I'm not looking
for any proprietary formulation info, just final analyses.)

If there is no particular oxide that correlates with heating,
then maybe vitrification alone is the thing. I guess one
way to test that might be to fire the same body at
different cones. I hope to look into that after I do a few
glaze tests.

Many thanks!





Bob Masta

potsATdaqartaDOTcom

Jon Pacini on tue 21 feb 06


Greetings all, Hi Bob---I found this in the clayart archive under--- Leaky,
weepy test results--Jiri's iron questionif you want to check out the entire
thread you can find it there from this date Fri, 27 Feb 2004 10:58:34 -0800
and back track a bit.Enjoy---jonp
Greetings all
I ran some microwave tests on some clays of various absorption and Iron
content. These are unglazed samples that are the standards we use for
comparing our daily QA tests. They are not fresh from the kiln, they have
been sitting in a cupboard for a while. They have not been soaked in water.

Ambient temp at the time of the test is 68*F, humidity is 83% barometer is
29.98 and rising. The thermometer used is a digital K-type the microwave is
a magic chef carousel type. I heated the tests for 90 seconds on a glass
tray, on removing from the oven I took the readings and here they are.

Clay color Absorp. % temp *F
Em210 white 17 125
Em235 red 22 129
Em217 buff 10 133

Wc397 white 6 135
Wc401 white 2.3 142
Wc394 red 2 148

Wc893 white 1 152
Wc811 red 2.1 155

Now---you can draw whatever conclusions you want from this test. But if you
take a mug out of the cupboard and heat it up I d bet you d get similar
results. If you want to soak it in boiling water for 2-6 hrs and perform
this test, then that s a no brainer. The mugs with the highest absorption
are going to be hottest.

As for the Iron issue, there seems to be somewhat of a correlation with
this, admittedly limited, data. I also tried a glzed raku pot with a splash
of reduced copper glaze on it to see what might happen. The portions of the
pot with no glaze reached 129*F, with clear glaze 135*F and the reduced
copper glaze got up to 254*F.

Best regards
Jon Pacini
Clay Manager
Laguna Clay Co

Bob Masta on wed 22 feb 06


Jon, those are indeed the test results I was referring to;
I had found them in the archives as you originally
suggested. Thanks again for the re-post.

But my real question is about the oxide analyses
for each of these bodies, so that we can look for
correlations with heating. Any chance of getting
those?

Many thanks!

Bob Masta

potsATdaqartaDOTcom