Rosanne Cleveland-King on thu 14 aug 97
I am doing a special order of many dog bowls with an extra
applied strip imprinted with leather stamps. I have been
applying the strip at the just less than leather hard stage, and
using a strip made with the slab roller and very carefully
applying it with slip and drying under plastic slowly. More
than half had cracks in the strips, so I made them again and put
the strips on rather wet bowls. The same thing happened. I
don't feel that I am stressing the strip in any way. Should I
be extruding the strip, or maybe wedging it first? Any
suggestions?
Thanks,
Rosanne
Darrol Shillingburg on fri 15 aug 97
Hi Rosanne,
I made some large banded planters some time ago. Dried them faster on the
inside than on the outside, completely eliminated cracked bands. I used
plastic bags with the bottoms cut off and dried them outside in the shade.
The inner light bulb trick, mentioned here a couple of days ago would work
also.
Good luck,
Darrol in Elephant Butte, NM
----------
> From: Rosanne Cleveland-King
>
> ----------------------------Original message----------------------------
> I am doing a special order of many dog bowls with an extra
> applied strip imprinted with leather stamps. I have been
> applying the strip at the just less than leather hard stage, and
> using a strip made with the slab roller and very carefully
> applying it with slip and drying under plastic slowly. More
> than half had cracks in the strips, so I made them again and put
> the strips on rather wet bowls. The same thing happened. I
> don't feel that I am stressing the strip in any way. Should I
> be extruding the strip, or maybe wedging it first? Any
> suggestions?
>
> Thanks,
>
> Rosanne
Judy Musicant on fri 1 nov 02
Hello again, After my post yesterday on my flat bottomed pieces cracking, I took another look and realized that all the cracking has occurred with only one glaze - a copper carbonate green that I've been using for years with no particular cracking problems. Could it be a glaze fit problem all of a sudden? The other strange thing is that I use the same base glaze with cobalt, and with a yellow mason stain, and have not had these cracking problems. Copper is a flux, yes? Could the way the copper is interacting with the glaze suddenly be a problem? I do have a new bucket of the green mixed up. Perhaps I'll try that and see what happens.
Judy
Judy Musicant on sat 9 aug 08
Hello Potters,
I'm hoping that some of you can provide me with some insight as to why, =
after 30 years of potting, I'm getting S cracks in almost all of my =
larger (10" and larger) bowls. Most - but not all - of my smaller bowls =
are not cracking. This has been going on for 6 months or so - I'm using =
the same clay - Standard 112. I wedge the same way, lay the cone of =
clay down sideways on the wheel (which is what Steven Hill suggests to =
avoid cracking), I compress the bottom, etc. I would have guessed it is =
something in the latest batch from Standard, but my studiio partner, who =
uses the same clay, is not having this problem. I'm going nuts, as you =
can imagine. Thanks for any thoughts.
Judy Musicant
Pottersguildnj.org
Vince Pitelka on sat 9 aug 08
Judy Musicant wrote:
"I'm hoping that some of you can provide me with some insight as to why,
after 30 years of potting, I'm getting S cracks in almost all of my larger
(10" and larger) bowls. Most - but not all - of my smaller bowls are not
cracking. This has been going on for 6 months or so - I'm using the same
clay - Standard 112. I wedge the same way, lay the cone of clay down
sideways on the wheel (which is what Steven Hill suggests to avoid
cracking), I compress the bottom, etc. I would have guessed it is something
in the latest batch from Standard, but my studiio partner, who uses the same
clay, is not having this problem. I'm going nuts, as you can imagine.
Thanks for any thoughts."
Judy -
If the cracks are truly "S"-shaped, across and centered on the bottom, then
they are definitely shrinkage cracks. How do you compress the bottoms? How
quickly do you throw these bowls? I always compress the bottoms of my bowls
and plates with a stiff rubber or rigid wood rib. Throwing quickly allows
less opportunity for water to soak into the pot. But since you did not have
this problem before, that is probably not the answer. Is there anything
else you can think of that has changed in the way you make these bowls?
Do you wire the bowls off the bat right after throwing, and do you do it
with the wheel turning? If not, I suggest that you do that. We mix all our
own claybodies at the Craft Center so I am not familiar with Standard 112,
but they make very good clays, so you might want to call them and ask for
their opinion as well. If this is an especially plastic body, then when you
wire the bowls off right away they may be re-sticking, especially the larger
ones, and it may help to wire them off again after a few hours. I would put
them back on the wheel and do this with the wheel turning. With some
claybodies, wiring off the pots with the wheel standing still can be enough
to set up a linear grain structure that is enough to cause cracking. I
always wire off my pots with the wheel turning, and teach my students to do
the same.
I wish you the best of luck in solving this problem -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Larry Kruzan on sat 9 aug 08
Hi Judy,
Have you changed bats, or the amoiunt of time you leave the bowls on bats. Wood bats are very forgiving but plastic bats give me greif with S-cracks.
Larry
-------------- Original message --------------
From: Judy Musicant
> Hello Potters,
> I'm hoping that some of you can provide me with some insight as to why, after 30
> years of potting, I'm getting S cracks in almost all of my larger (10" and
> larger) bowls. Most - but not all - of my smaller bowls are not cracking. This
> has been going on for 6 months or so - I'm using the same clay - Standard 112.
> I wedge the same way, lay the cone of clay down sideways on the wheel (which is
> what Steven Hill suggests to avoid cracking), I compress the bottom, etc. I
> would have guessed it is something in the latest batch from Standard, but my
> studiio partner, who uses the same clay, is not having this problem. I'm going
> nuts, as you can imagine. Thanks for any thoughts.
>
> Judy Musicant
> Pottersguildnj.org
Kelly Savino on sat 9 aug 08
Judy Musicant wrote:
>I'm hoping that some of you can provide me with some insight as to why,
after 30 years of potting, I'm getting S cracks in almost all of my
larger (10" and larger) bowls.
Judy, this is a total shot in the dark, but have you changed your kiln
wash, or do you need a new coat? Check the feet of your pot for
plucking, little chippy looking spots on the outside of the foot ring
where it stuck to the kiln shelf while shrinking. It occurs to me that
the same kind of shrinking-while-stuck might cause a bottom to split.
Wild stab, fwiw.
Yours
Kelly
http://www.primalpotter.com
Lynn Goodman Porcelain Pottery on sat 9 aug 08
Hi Judy,
Have you changed your bats recently? When I briefly used plastic bats
I had a problem; going back to plaster bats fixed it.
Lynn
> Hello Potters,
> I'm hoping that some of you can provide me with some insight as to
> why, after 30 years of potting, I'm getting S cracks in almost all
> of my larger (10" and larger) bowls. Most - but not all - of my
> smaller bowls are not cracking.
> I would have guessed it is something in the latest batch from
> Standard, but my studiio partner, who uses the same clay, is not
> having this problem.
Lynn Goodman
Fine Porcelain Pottery
Cell 347-526-9805
www.lynngoodmanporcelain.com
Antoinette Badenhorst on sat 9 aug 08
Judy, I recall a problem with standard 112 a few years back. Is your partner throwing the same as you? Did you change something in your way of throwing , maybe because of a soreness or something of that sort? I am shooting wild here, since I do not have the answer, but maybe asking these kind of questions might help you locate the problem.
I will contact Standard and make them aware of your problem and ask them to test it.
I hope this help some.
--
Antoinette Badenhorst
www.clayandcanvas.com
www.studiopottery.co.uk
-------------- Original message ----------------------
From: Judy Musicant
> Hello Potters,
> I'm hoping that some of you can provide me with some insight as to why, after 30
> years of potting, I'm getting S cracks in almost all of my larger (10" and
> larger) bowls. Most - but not all - of my smaller bowls are not cracking. This
> has been going on for 6 months or so - I'm using the same clay - Standard 112.
> I wedge the same way, lay the cone of clay down sideways on the wheel (which is
> what Steven Hill suggests to avoid cracking), I compress the bottom, etc. I
> would have guessed it is something in the latest batch from Standard, but my
> studiio partner, who uses the same clay, is not having this problem. I'm going
> nuts, as you can imagine. Thanks for any thoughts.
>
> Judy Musicant
> Pottersguildnj.org
MaryU on sun 10 aug 08
Hi Judy,
I use 112 as well and haven't had those problems lately. I believe the
secret is letting the bowl dry slowly and sllowing the bottom to catch up by
loosely wrapping the rim of the bowl. If you have inconsistent drying, the
bowl will distort and subsequently crack.
Good Luck.
Mary
----- Original Message -----
From: "Judy Musicant"
To:
Sent: Saturday, August 09, 2008 9:34 AM
Subject: Cracking problem
Hello Potters,
I'm hoping that some of you can provide me with some insight as to why,
after 30 years of potting, I'm getting S cracks in almost all of my larger
(10" and larger) bowls. Most - but not all - of my smaller bowls are not
cracking. This has been going on for 6 months or so - I'm using the same
clay - Standard 112. I wedge the same way, lay the cone of clay down
sideways on the wheel (which is what Steven Hill suggests to avoid
cracking), I compress the bottom, etc. I would have guessed it is something
in the latest batch from Standard, but my studiio partner, who uses the same
clay, is not having this problem. I'm going nuts, as you can imagine.
Thanks for any thoughts.
Judy Musicant
Pottersguildnj.org
Judy Musicant on mon 11 aug 08
Vince Pitelka wrote:
"Judy -
If the cracks are truly "S"-shaped, across and centered on the bottom, =
then
they are definitely shrinkage cracks."
Maybe I misled all you kind folks who responded to my question on and =
off list. The cracks are not really "S" shaped. They're more straight =
or a little curved. The bad ones are centered on the bottm, but many =
are off to the side on the bottom and don't cross the center at all. =
What to do, what to do?
Judy
Michael Wendt on tue 12 aug 08
Judy,
Try stack and slam wedging 10 doublings
after you spiral wedge, keeping the stacks
in the same plane as the wheel head and see if
this solves the problem.
If 10 is not enough, try 20 next. At some point
you will discover the cracking disappears.
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave.
Lewiston, Id 83501
U.S.A.
208-746-3724
wendtpot@lewiston.com
http://www.wendtpottery.com
http://UniquePorcelainDesigns.com
James and Sherron Bowen on tue 12 aug 08
Have you given any consideration to adding nylon fiber to your clay for
these pieces?
Jim
----- Original Message -----
From: "Michael Wendt"
To:
Sent: Tuesday, August 12, 2008 12:17 PM
Subject: Re: cracking problem
> Judy,
> Try stack and slam wedging 10 doublings
> after you spiral wedge, keeping the stacks
Lee Love on wed 13 aug 08
On 8/13/08, James and Sherron Bowen wrote:
> Have you given any consideration to adding nylon fiber to your clay for
> these pieces?
>
Or, just a disc of paper clay on the inside bottom, smoothed in.
--
Lee Love in Minneapolis
http://mashikopots.blogspot.com/
http://claycraft.blogspot.com/
"Let the beauty we love be what we do.
There are hundreds of ways to kneel and kiss the ground." --Rumi
Elisabeth Maurland on mon 12 mar 12
Hi Lis,
Are the cracks around the foot? I had cracks that ran around the foot on =
=3D
larger bowls. Small bowls were fine. I still don't know what caused it, =3D
but I stopped it from happening by throwing the feet instead of trimming =
=3D
them.=3D20
(Any guesses as to why it happened? Some kind of stress in the =3D
difference in thickness in the wall right there, maybe?)
Elisabeth
On Mar 12, 2012, at 8:10 AM, Lis Allison wrote:
> Hello Clay Gurus,
>=3D20
> I just fired a batch of bowls, cone 6, for someone. He's not a very
> experienced potter, but not a beginner either. A number of his bowls =3D
show
> cracks running around (along the throwing lines), outside but not =3D
inside,
> the bowls.
>=3D20
> What can I tell him to help him solve this problem? I have never had =3D
it
> myself so I don't know exactly what is wrong.
>=3D20
> Help, please!
>=3D20
> Lis
> --
> Elisabeth Allison
> Pine Ridge Studio
> website: www.pine-ridge.ca
> Pottery blog: www.studio-on-the-ridge.blogspot.com
> Garden blog: www.garden-on-the-ridge.blogspot.com
Elisabeth=3D20
www.elisabethmaurland.com
Lis Allison on mon 12 mar 12
Hello Clay Gurus,
I just fired a batch of bowls, cone 6, for someone. He's not a very
experienced potter, but not a beginner either. A number of his bowls show
cracks running around (along the throwing lines), outside but not inside,
the bowls.
What can I tell him to help him solve this problem? I have never had it
myself so I don't know exactly what is wrong.
Help, please!
Lis
--
Elisabeth Allison
Pine Ridge Studio
website: www.pine-ridge.ca
Pottery blog: www.studio-on-the-ridge.blogspot.com
Garden blog: www.garden-on-the-ridge.blogspot.com
Greg Relaford on mon 12 mar 12
I'm interested in knowing more about this too. I recently had this happen
on a couple pots. My theory, based recall of throwing these particular
pieces, was that the cracks formed where I had stressed the pot inward with
the clay having been worked too long (and possibly too wet.) For example
moving the sides out, then back again. FWIW, metals seem to do something
similar when stressed near breaking, and left bent. The heat makes it
visible via contraction.
Just my theory.
On Mar 12, 2012 6:40 AM, "Lis Allison" wrote:
> Hello Clay Gurus,
>
> I just fired a batch of bowls, cone 6, for someone. He's not a very
> experienced potter, but not a beginner either. A number of his bowls show
> cracks running around (along the throwing lines), outside but not inside,
> the bowls.
>
> What can I tell him to help him solve this problem? I have never had it
> myself so I don't know exactly what is wrong.
>
> Help, please!
>
> Lis
> --
> Elisabeth Allison
> Pine Ridge Studio
> website: www.pine-ridge.ca
> Pottery blog: www.studio-on-the-ridge.blogspot.com
> Garden blog: www.garden-on-the-ridge.blogspot.com
>
ronroy@CA.INTER.NET on mon 12 mar 12
Hi Liz,
If it's cracking in the glaze that way I predict shivering. If I can
see the recipe for the glaze it will help.
RR
Quoting Lis Allison :
> Hello Clay Gurus,
>
> I just fired a batch of bowls, cone 6, for someone. He's not a very
> experienced potter, but not a beginner either. A number of his bowls show
> cracks running around (along the throwing lines), outside but not inside,
> the bowls.
>
> What can I tell him to help him solve this problem? I have never had it
> myself so I don't know exactly what is wrong.
>
> Help, please!
>
> Lis
> --
> Elisabeth Allison
> Pine Ridge Studio
> website: www.pine-ridge.ca
> Pottery blog: www.studio-on-the-ridge.blogspot.com
> Garden blog: www.garden-on-the-ridge.blogspot.com
>
Liz Gowen 1 on mon 12 mar 12
What type of clay was it. I had a similar problem with a cone 6 porcelain.
It also cracked very thin cracks at the rim, with wider bowl shapes. It
really seemed to have no strength as it dried. It was suggested I try some
white bentonite which I am hoping to try this week to use up the rest of
this batch of clay. I think I will also pug in some cone 10 clay since it
didn't behave well in the ^6 gas firing even when I fired to a barely
^6...at 2 o'clock. Was planning on switching clay to a cone 10 body that ha=
s
a lot of dry strength but is harder to carve with the hands still being
sore. I do carve dry and spritz the piece as I carve but also found this ^1=
0
clay distorts my already carved lines when I spritz the area to carve more.
The ^6 clay did not. I am in a bit of a quandary. Both are commercially
available clays so we can't compare and see what is making one have better
dry strength. This is where it would be nice to have a reduction test kiln
and not have to fill the larger kiln with all this testing. I remember
Lawrence Ewing said when he went back to full time studio work he built a
1cubic foot test kiln within his gas kiln to test all the new glazes.
Lawrence are you still on the list? don't remember if it was done with bric=
k
or fiber or how the burner worked for it....Liz Gowen
Subject: Cracking problem
Hello Clay Gurus,
I just fired a batch of bowls, cone 6, for someone. He's not a very
experienced potter, but not a beginner either. A number of his bowls show
cracks running around (along the throwing lines), outside but not inside,
the bowls.
What can I tell him to help him solve this problem? I have never had it
myself so I don't know exactly what is wrong.
Help, please!
Lis
--
Elisabeth Allison
Pine Ridge Studio
website: www.pine-ridge.ca
Pottery blog: www.studio-on-the-ridge.blogspot.com
Garden blog: www.garden-on-the-ridge.blogspot.com
Lis Allison on tue 13 mar 12
Thank you Clayarters for the suggestions! I've chatted with my friend a
bit more and I think his wedging may be a large part of the problem. Then
his throwing is very slow and he uses a lot of water.... part of his
problem is that in a class situation the instructor doesn't have the time
to coach him, and his speech is very slow and hard to understand.
So thank you all for the help. I'd never seen cracks that were only on the
outsides of bowls before, so didn't know what was wrong. Learn something
new every day!
Lis
--
Elisabeth Allison
Pine Ridge Studio
website: www.pine-ridge.ca
Pottery blog: www.studio-on-the-ridge.blogspot.com
Garden blog: www.garden-on-the-ridge.blogspot.com
| |
|
