LINDA BLOSSOM on wed 26 feb 97
Thanks David for sharing your experiences with planters. I do see that
there is a difference between 06 and a stoneware range in terms of
durability. The grog ( increasing life span of the piece) does make sense
if you take it in the light of what Cushing says. Remember, I am just
evaluating what I read and hear - I'll put those guys outside to find out
myself. I did put a cone 6 planter outside that was probably not over 5/8"
thick and so far it is fine. It has not been a difficult winter in usual
terms - however, the freeze and thaw has been constant. This is in
contrast to past winters which were almost all freeze. I would think that
this winter would be the best kind to judge planters. I should point out
that I use the word terra cotta a bit loosely. I realize it can mean a
lower fired red and sometimes I use it to refer to unglazed red clay. I
formulate a cone 6 stoneware body to be red. Just for the information,
I'll quote part of what is in the Cushing Handbook:
"If water, which is trapped in the pores has "escape tunnels" which will
take up the expansion when ice is formed, the piece will not crack. The
solution then is to have a clay body with a pore structure, with enough
capillaries for expansion to "squirt" out into these veins without
confining the pressure caused by freezing water. If the ice can expand and
contract freely the piece will not crack...." He goes on to give the method
for determining if a clay meets this criteria. There is also some
interesting information before this paragraph, but this one gives the
essence of the information.
Thanks also to Ric Swenson for his answer. It was interesting to find out
that industry had an absorption standard for earthenware and stoneware. In
answer to your question. Ric, why one would leave a planter outside. The
planter I have outside is pretty large and would have to be emptied to be
brought in. It has perennial herbs in it that I would like to leave there.
Also, I have to admit, it was sort of a test.. It just occurred to me
that glaze would defeat the purpose of the open body in the previous
paragraph...Maybe I am missing something there. Glazed on one side only -
both sides...Must quit thinking for a moment and pay some bills. Just
realized that Ric's answer wasn't on the list. He worked at a pottery that
made a LOT of planters and they used 3% absorption for stoneware and 5% for
lower fired. Just included that so no one would be confused on what I said
above in this paragraph.
I was told several years ago by a person who sold tile that glazed tile
couldn't be used outside because the moisture from below would force the
glaze off. Where does it all come from? With that rule in mind, I promptly
made some glazed things to put outside. You would never know I was raised
in the 50's to be an obedient little baby boomer.
Linda Blossom
Ithaca, NY
Laura Freedman on wed 26 feb 97
LINDA BLOSSOM wrote:
>
> ----------------------------Original message----------------------------
> Thanks David for sharing your experiences with planters. I do see that
> there is a difference between 06 and a stoneware range in terms of
> durability. The grog ( increasing life span of the piece) does make sense
> if you take it in the light of what Cushing says. Remember, I am just
> evaluating what I read and hear - I'll put those guys outside to find out
> myself. I did put a cone 6 planter outside that was probably not over 5/8"
> thick and so far it is fine. It has not been a difficult winter in usual
> terms - however, the freeze and thaw has been constant. This is in
> contrast to past winters which were almost all freeze. I would think that
> this winter would be the best kind to judge planters. I should point out
> that I use the word terra cotta a bit loosely. I realize it can mean a
> lower fired red and sometimes I use it to refer to unglazed red clay. I
> formulate a cone 6 stoneware body to be red. Just for the information,
> I'll quote part of what is in the Cushing Handbook:
>
> "If water, which is trapped in the pores has "escape tunnels" which will
> take up the expansion when ice is formed, the piece will not crack. The
> solution then is to have a clay body with a pore structure, with enough
> capillaries for expansion to "squirt" out into these veins without
> confining the pressure caused by freezing water. If the ice can expand and
> contract freely the piece will not crack...." He goes on to give the method
> for determining if a clay meets this criteria. There is also some
> interesting information before this paragraph, but this one gives the
> essence of the information.
>
> Thanks also to Ric Swenson for his answer. It was interesting to find out
> that industry had an absorption standard for earthenware and stoneware. In
> answer to your question. Ric, why one would leave a planter outside. The
> planter I have outside is pretty large and would have to be emptied to be
> brought in. It has perennial herbs in it that I would like to leave there.
> Also, I have to admit, it was sort of a test.. It just occurred to me
> that glaze would defeat the purpose of the open body in the previous
> paragraph...Maybe I am missing something there. Glazed on one side only -
> both sides...Must quit thinking for a moment and pay some bills. Just
> realized that Ric's answer wasn't on the list. He worked at a pottery that
> made a LOT of planters and they used 3% absorption for stoneware and 5% for
> lower fired. Just included that so no one would be confused on what I said
> above in this paragraph.
>
> I was told several years ago by a person who sold tile that glazed tile
> couldn't be used outside because the moisture from below would force the
> glaze off. Where does it all come from? With that rule in mind, I promptly
> made some glazed things to put outside. You would never know I was raised
> in the 50's to be an obedient little baby boomer.
>
> Linda Blossom
> Ithaca, NY
--------
Linda, I am interested in which clay bodies can be left outside in a
north eastern climate. I want to set tiles out and don't know whether a
cone 6 is adequate (which is what I usually fire to) or ^10 would be
better. In the past I have been told stoneware would be fine outside in
my winter area, PA. I too left two hanging planters outside this winter.
The stoneware cracked and the low fire didn't. That wasn't supposed to
happen. If you have any concrete info, or anyone else does, please set
me straight.
TIA lauras@epix.net
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