Jan McQueary on wed 13 dec 00
Did you let the boiled tiles cool in the water? If not, some of the
water will probably steam out of them before they cool. (My father
always taught us to wash scissors and such with very hot water - so that
the water on the blades and in the joint would evaporate faster and they
would dry quicker.
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PAGCarr@AOL.COM on wed 13 dec 00
After losing a substantial portion of a commission last year because my tile=
s=20
were warping and cracking, I decided to find a new claybody. I have been=20
testing several high fire white bodies for warping, shrinkage and absorption=
=20
using the procedure outlined in Outdoor Weather Resistant Ceramics on the=20
Digitalfire website. One of the clays in which I was particularly intereste=
d=20
was Tucker's White Sculpture/Raku. At =E2=88=868(ox), I have measured the s=
hrinkage=20
at 10%, with a 24hr soak absorption of 3.04% and a 5 hour boil absorption of=
=20
2.81%. In other words, the tiles that were soaked absorbed more water=20
(weighed more), than the same tile which was then boiled in water for 5=20
hours. So, not only did these tiles appear to have no closed porosity, but=20
the open porosity appears to be reduced after boiling. Why??? Have I misse=
d=20
something?
I repeated these test 3 different times on 6 different tiles, all clearly=20
labeled. The data is completely reproducible. (In my former life I was an=20
experimental chemist, so I do know how to read an Ohaus balance, and how to=20
take data.)
During the boil periods, the tiles were always immersed in boiling water. =20
After the 5 hours, the tiles were cooled and the water wiped from the=20
surface, so that the temperatures of the tiles were roughly the same at the=20
time of weighing, whether they were soaked or boiled.
Additionally, I found the same behavior in Kickwheel Pottery's #271 (two=20
different batches) and ART's Porcelain 135. Is this the behavior I should=20
expect for clays fired close to or to the point of maturity/vitrification?
My hypothesis: the fired clay matrix has no capilliary-like networks, and=20
that at higher temperatures, some of the absorbed water boils out of the ope=
n=20
pores. =20
The saturation coefficient is >1 (is this physically meaningful?) and >>.78.=
=20
How can I predict the survivability of this clay in freeze-thaw conditions?=20
Clearly, this doesn't pass CSA and ASTM specs for outdoor use.
Thank you, in advance for your comments!
Paulette Carr
pagcarr@aol.com
St. Louis =20
Snail Scott on wed 13 dec 00
I noticed that the test samples that I boiled dried out very=20
quickly from their own heat, even before I could weigh them.
In fact, I could run them under water and watch them get wet
again. So now that's what I do. I keep them wet until cool,
and then weigh them. (I haven't compared soak results to boil=20
results, but clearly I need to!) I have also noticed that when=20
doing freeze tests, the tests dry out quite a bit. Now I do my=20
freeze tests in ziploc bags.
-Snail=20
At 02:55 PM 12/13/00 EST, you wrote:
>After losing a substantial portion of a commission last year because my
tiles=20
>were warping and cracking, I decided to find a new claybody. I have been=
=20
>testing several high fire white bodies for warping, shrinkage and=
absorption=20
>using the procedure outlined in Outdoor Weather Resistant Ceramics on the=
=20
>Digitalfire website. One of the clays in which I was particularly
interested=20
>was Tucker's White Sculpture/Raku. At =E2=88=868(ox), I have measured the
shrinkage=20
>at 10%, with a 24hr soak absorption of 3.04% and a 5 hour boil absorption=
of=20
>2.81%. In other words, the tiles that were soaked absorbed more water=20
>(weighed more), than the same tile which was then boiled in water for 5=20
>hours. So, not only did these tiles appear to have no closed porosity, but=
=20
>the open porosity appears to be reduced after boiling. Why??? Have I
missed=20
>something?
>
>I repeated these test 3 different times on 6 different tiles, all clearly=
=20
>labeled. The data is completely reproducible. (In my former life I was an=
=20
>experimental chemist, so I do know how to read an Ohaus balance, and how to=
=20
>take data.)
>
>During the boil periods, the tiles were always immersed in boiling water. =
=20
>After the 5 hours, the tiles were cooled and the water wiped from the=20
>surface, so that the temperatures of the tiles were roughly the same at the=
=20
>time of weighing, whether they were soaked or boiled.
>
>Additionally, I found the same behavior in Kickwheel Pottery's #271 (two=20
>different batches) and ART's Porcelain 135. Is this the behavior I should=
=20
>expect for clays fired close to or to the point of maturity/vitrification?
>
>My hypothesis: the fired clay matrix has no capilliary-like networks, and=
=20
>that at higher temperatures, some of the absorbed water boils out of the
open=20
>pores. =20
>
>The saturation coefficient is >1 (is this physically meaningful?) and
>>.78. =20
>How can I predict the survivability of this clay in freeze-thaw conditions?=
=20
>Clearly, this doesn't pass CSA and ASTM specs for outdoor use.
>
>Thank you, in advance for your comments!
>Paulette Carr
>pagcarr@aol.com
>St. Louis =20
>
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