Laurie Furumoto on sun 20 feb 11
I've been having trouble with coil work bowls/platters cracking in the cen=
=3D
ter and around the base disc of clay. I teach high school ceramics and I'v=
=3D
e been doing a lesson on Mimbres southwestern style coil bowls with slip de=
=3D
coration. The first time I taught the unit it went great and the kids bowl=
=3D
s came out beautifully. The next year I taught the unit, every single one =
=3D
on my kids' bowls cracked. I had been having other problems with the clay =
=3D
that term and blamed the clay (LAGUNA em 210). I contacted Laguna and they=
=3D
had no idea what could cause it, but recommended I switch to a more plasti=
=3D
c soldate-60 clay which I did. I taught a coil unit with new clay during t=
=3D
he first semester with closed forms, vases, etc and again they came out gre=
=3D
at. I went back to the Mimbres unit second term and my kids work is cracki=
=3D
ng again.
Why did this unit go so well the first time I taught it and so badly since?=
=3D
The only significant thing I've done differently is to use an extruder to=
=3D
pull the coils. The coils come out big and I have the kids roll them out =
=3D
a little to get the right thickness. Could this be my mistake? Also, I bu=
=3D
y clay at the beginning of term - I live in Hawaii and shipping kills so I =
=3D
order for the whole year. Both times the cracking occurred second semester=
=3D
so the clay was about 5-6 months old. The time it worked was the first ye=
=3D
ar I taught here and I had to order clay second term, so it was fresher. C=
=3D
ould this be my problem? I've been wedging it before it goes into the extr=
=3D
uder.
I'm bummed, their slip designs are awesome, and to have the coilwork crack =
=3D
under it is disappointing to all of us.
Vince Pitelka on sun 20 feb 11
Laurie Furumoto
I've been having trouble with coil work bowls/platters cracking in the
center and around the base disc of clay. I teach high school ceramics and
I've been doing a lesson on Mimbres southwestern style coil bowls with slip
decoration. - - - - - - I'm bummed, their slip designs are awesome, and to
have the coilwork crack under it is disappointing to all of us."
Laurie -
I can imagine your disappointment. If the clay was very fresh the first
time and it worked fine, that could be the problem with the later work. In
order for coil construction to work as well as possible without having to
score and slurry between each coil, which wastes so much time and is
unnecessary, the clay needs to be very moist and plastic, and the coils nee=
d
to be smeared together. Also, are you building on top of the slab you star=
t
with? That is pretty essential. If you coil around the outside of the
initial slab, there is no way to get a good bond, and that is almost a
certain crack. If you score and slurry that first coil addition on top of
the bottom slab, then you can smear the coils together from there. You can
still work the coils outward with a rib or hand and get a smooth curvature
in the bottom of the bowl.
I hope this helps.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
John Post on sun 20 feb 11
To add to what Vince wrote, I have seen many art teachers start coil
pottery by having the kids create a spiral coil for the base of the
pot. This always leads to a cracked base.
If this is what you had the kids do, you could have them remake the
pots, and this time make the base by rolling out a slab and building
up and/or out as Vince recommends.
The kids I teach have no problem starting something a second time and
the experience they gained from the first attempt usually yields
better work the second time around.
John Post
Sterling Heights, Michigan
http://www.johnpost.us
Follow me on Twitter
https://twitter.com/UCSArtTeacher
> Also, are you building on top of the slab you start
> with? That is pretty essential. If you coil around the outside of
> the
> initial slab, there is no way to get a good bond, and that is almost a
> certain crack. If you score and slurry that first coil addition on
> top of
> the bottom slab, then you can smear the coils together from there.
> You can
> still work the coils outward with a rib or hand and get a smooth
> curvature
> in the bottom of the bowl.
>
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net; wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka
Mike on mon 21 feb 11
Hi Laurie,
I don't know the specifics of your coil building technique, but I get
the cracks across and around the base when the rim and walls dry too
quickly. When this is in danger of happening, I turn the vessels over
and dry them on their lips as soon as they are stiff enough not to
deform. When the weather is really dry, I'll then throw a piece of
cloth over them to slow the process even further. This may be a dumb
question, but is your second semester generally a drier time of the year?
In my experience, using a more plastic clay only exacerbates the
problem. I can't imagine that the clay being a few months older could
possibly be the cause. The mention of closed forms coming out ok makes
me think that drying speed is the problem.
Mike
in Taku, Japan
http://karatsupots.com
http://karatsupots.blogspot.com
Workshop in Taku, Spring 2012: To Be Announced
(2011/02/21 8:53), Laurie Furumoto wrote:
> I've been having trouble with coil work bowls/platters cracking in the c=
enter and around the base disc of clay. I teach high school ceramics and I=
've been doing a lesson on Mimbres southwestern style coil bowls with slip =
decoration. The first time I taught the unit it went great and the kids bo=
wls came out beautifully. The next year I taught the unit, every single on=
e on my kids' bowls cracked. I had been having other problems with the cla=
y that term and blamed the clay (LAGUNA em 210). I contacted Laguna and th=
ey had no idea what could cause it, but recommended I switch to a more plas=
tic soldate-60 clay which I did. I taught a coil unit with new clay during=
the first semester with closed forms, vases, etc and again they came out g=
reat. I went back to the Mimbres unit second term and my kids work is crac=
king again.
>
> Why did this unit go so well the first time I taught it and so badly sinc=
e? The only significant thing I've done differently is to use an extruder =
to pull the coils. The coils come out big and I have the kids roll them ou=
t a little to get the right thickness. Could this be my mistake? Also, I =
buy clay at the beginning of term - I live in Hawaii and shipping kills so =
I order for the whole year. Both times the cracking occurred second semest=
er so the clay was about 5-6 months old. The time it worked was the first =
year I taught here and I had to order clay second term, so it was fresher. =
Could this be my problem? I've been wedging it before it goes into the ex=
truder.
>
> I'm bummed, their slip designs are awesome, and to have the coilwork crac=
k under it is disappointing to all of us.
>
Vince Pitelka on mon 21 feb 11
Mike in Taku wrote:
"In my experience, using a more plastic clay only exacerbates the =3D
problem. I can't imagine that the clay being a few months older could =3D
possibly be the cause. The mention of closed forms coming out ok makes =3D
me think that drying speed is the problem."
Hi Mike -=3D20
To say that a more plastic clay exacerbates the problem is pretty much =3D
counter to most coil-construction technique and logic. You certainly do =
=3D
not want a high-shrinkage clay for any handbuilding process, but a very =3D
plastic body with a generous amount of sand or grog is ideal. =3D
Plasticity equals adhesion. =3D20
There's certainly no problem with clay being old, but if it has lost any =
=3D
moisture content, then that becomes a serious problem. And even with =3D
old clay that still has adequate moisture, it would be essential to =3D
mobilize it by thorough wedging or re-pugging.
As I remember, she also said that she was extruding the coils, and that =3D
might be a problem as well. As a matter of personal philosophy I would =3D
never use extruded coils for a handbuilt coil pot, and I think that =3D
hand-rolled coils become more mobile and compacted, and that will =3D
benefit the joinery. =3D20
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu=3D20
http://iweb.tntech.edu/wpitelka
Hank Murrow on tue 22 feb 11
On Feb 22, 2011, at 4:37 PM, Mike Gordon wrote:
> HOW about pictures??????? Mike Gordon
Dear mike; Clayart does not support pics, so one must ask privately. =3D
Cheers, Hank
> On Feb 22, 2011, at 1:36 PM, Hank Murrow wrote:
>=3D20
>> On Feb 22, 2011, at 10:40 AM, Sharon Wetherby wrote:
>>=3D20
>>> Vince Pitelka wrote, "As I remember, she also said that she was =3D
extruding
>>> the coils, and that might be a problem as well. As a matter of =3D
personal
>>> philosophy I would never use extruded coils for a handbuilt coil =3D
pot, and I
>>> think that hand-rolled coils become more mobile and compacted, and =3D
that will
>>> benefit the joinery."
>>>=3D20
>>> I used extruded coils in a classroom environment about a year or two =
=3D
ago.
>>> My coils cracked as did nearly all the other students' coils. This =3D
is the
>>> only time I've had problems with coils cracking, and it's the only =3D
time I've
>>> used extruded coils. We blamed it on the clay. So, now I know.....
>>> Thanks, Vince.
>>=3D20
>> Perhaps the plastic nature of throwing clays works against hand =3D
joining processes.
>>=3D20
>> While on Crete last Fall, I saw a 19 year-old potter named Niko take =3D
fresh three inch diameter pugs of their coarse clay and throw a 30" high =
=3D
x 26" wide bowl. He later added the same 3" fresh pugs of clay to the =3D
rim which had been stiffened with a huge propane torch, and threw =3D
another 24" to the top, making a 54" high Pith=3DE1ria(storage jar) Oh and =
=3D
by the way, he used a sidesaddle kickwheel to throw the bottom piece. =3D
The yard outside was full of these large jars, fired and ready for =3D
shipment....... all of them made on a kickwheel.
>>=3D20
>> These fellows can kick some ass with clay, my friends!
>>=3D20
>> Cheers, Hank
Deborah Thuman on tue 22 feb 11
I'm allergic to the wheel so I do a lot of coil building. I watched a
video on Ceramics Daily showing a Korean way to coil build. I don't do
the sides of the pot as the video showed, but I do the bottom of the
pot as the video showed. It's an easy technique to do but difficult to
explain.
I've discovered that making the bottom too thin is a sure way to get a
crack. Thicker is better. I also let my pots dry slowly under plastic.
Deb Thuman
http://debthumansblog.blogspot.com/
http://www.etsy.com/shop.php?user_id=3D5888059
http://www.facebook.com/pages/Deb-Thumans-Art-Page/167529715986
Sharon Wetherby on tue 22 feb 11
Vince Pitelka wrote, "As I remember, she also said that she was extruding
the coils, and that might be a problem as well. As a matter of personal
philosophy I would never use extruded coils for a handbuilt coil pot, and I
think that hand-rolled coils become more mobile and compacted, and that wil=
l
benefit the joinery."
I used extruded coils in a classroom environment about a year or two ago.
My coils cracked as did nearly all the other students' coils. This is the
only time I've had problems with coils cracking, and it's the only time I'v=
e
used extruded coils. We blamed it on the clay. So, now I know.....
Thanks, Vince.
Sharon
Hank Murrow on tue 22 feb 11
--Apple-Mail-43-128298050
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain;
charset=3Diso-8859-1
On Feb 22, 2011, at 10:40 AM, Sharon Wetherby wrote:
> Vince Pitelka wrote, "As I remember, she also said that she was =3D
extruding
> the coils, and that might be a problem as well. As a matter of =3D
personal
> philosophy I would never use extruded coils for a handbuilt coil pot, =3D
and I
> think that hand-rolled coils become more mobile and compacted, and =3D
that will
> benefit the joinery."
>=3D20
> I used extruded coils in a classroom environment about a year or two =3D
ago.
> My coils cracked as did nearly all the other students' coils. This is =
=3D
the
> only time I've had problems with coils cracking, and it's the only =3D
time I've
> used extruded coils. We blamed it on the clay. So, now I know.....
> Thanks, Vince.
Perhaps the plastic nature of throwing clays works against hand joining =3D
processes.
While on Crete last Fall, I saw a 19 year-old potter named Niko take =3D
fresh three inch diameter pugs of their coarse clay and throw a 30" high =
=3D
x 26" wide bowl. He later added the same 3" fresh pugs of clay to the =3D
rim which had been stiffened with a huge propane torch, and threw =3D
another 24" to the top, making a 54" high Pith=3DE1ria(storage jar) Oh and =
=3D
by the way, he used a sidesaddle kickwheel to throw the bottom piece. =3D
The yard outside was full of these large jars, fired and ready for =3D
shipment....... all of them made on a kickwheel.
These fellows can kick some ass with clay, my friends!
Cheers, Hank
--Apple-Mail-43-128298050
Content-Transfer-Encoding: 7bit
Content-Type: text/plain;
charset=3Dus-ascii
Niko and the kickwheel
--Apple-Mail-43-128298050
Content-Transfer-Encoding: 7bit
Content-Type: text/plain;
charset=3Dus-ascii
His buddy drying the rims
--Apple-Mail-43-128298050
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain;
charset=3Diso-8859-1
Finished Pith=3DE1ria, bottoms in the background. 25/day in Winter, 50/day =
=3D
in Summer.=3D
--Apple-Mail-43-128298050--
Carl Finch on wed 23 feb 11
At 06:41 PM 2/22/2011, Hank Murrow wrote:
>On Feb 22, 2011, at 4:37 PM, Mike Gordon wrote:
>
> > HOW about pictures???????
>
>Dear mike; Clayart does not support pics, so one must ask
>privately. Cheers, Hank
Waaay back in 2005 Holly Kilpatrick set up a Flickr account for
Clayart photos, drawings, etc.
Here are her instructions for using it:
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3Dfrom Clayart, Tue, 12 Sep 2006=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D
Instructions for posting photos to the Flickr Clayart site:
If you want to share a photo that would illustrate a discussion we are
having, or if you are trying to describe a glaze problem or display the
results of a glaze test, or show something in your studio, or whatever --
you don't have to disrupt your website, you don't have to sign up for a
photo account, all you have to do is:
Email your photo as an attachment to
French + 24 + ever at photos.flickr.com
(remove the spaces and remove the + signs and replace ' at '
with the at sign)
In the Email Subject, type the Title of your photo. Make it specific.
In the Body of the Email, type the Description of your photo, including you=
r
name and location. You can also put a link to your website in your
description if you want.
If you send an email to Clayart referencing a photo you have sent to
FlickR.com, you can provide the following link in your Clayart email, for
readers to see the photo you mention.
http://www.flickr.com/photos/clayart
If you want to view a particular Clayarter's photos, click on "Browse with
Clayart's tags" in the left-hand column, and you will see everyone's names.
You can print out this email for future reference. You are welcome to
contact me with comments/questions.
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3Dend=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
--Carl
Medford, Oregon
Mike on wed 23 feb 11
I had the chance to visit Korea last summer for the Celadon Festival in
Gangjin. There were potters everywhere using VERY firm extruded coils
and straps to make all sizes of pots. But,they wedged those coils in
well to the pot, paddled, and threw and stretched with a rib, so
everything was joined and compacted nicely.
There are all sorts of ways to coil build and I imagine that you will
need to make coils to match your clay and method. It probably takes some
experimentation. My work process involves working coils in on the inside
edge of the wall and pinching to the proper thickness, and paddling, but
usually little or no throwing. The best consistency for me is just firm
enough that the clay does not accumulate on my hands when I am extruding
the coils out from between the palms. Firmer works just as well from an
adhesion and cracking standpoint, but the hands get tired more quickly.
Those Korean potters with their firm coils must have forearms of steel.
Mike
in Taku, Japan
http://karatsupots.com
http://karatsupots.blogspot.com
(2011/02/23 6:36), Hank Murrow wrote:
> On Feb 22, 2011, at 10:40 AM, Sharon Wetherby wrote:
>
>> Vince Pitelka wrote, "As I remember, she also said that she was extrudin=
g
>> the coils, and that might be a problem as well. As a matter of personal
>> philosophy I would never use extruded coils for a handbuilt coil pot, an=
d I
>> think that hand-rolled coils become more mobile and compacted, and that =
will
>> benefit the joinery."
>>
>> I used extruded coils in a classroom environment about a year or two ago=
.
>> My coils cracked as did nearly all the other students' coils. This is t=
he
>> only time I've had problems with coils cracking, and it's the only time =
I've
>> used extruded coils. We blamed it on the clay. So, now I know.....
>> Thanks, Vince.
> Perhaps the plastic nature of throwing clays works against hand joining p=
rocesses.
>
> While on Crete last Fall, I saw a 19 year-old potter named Niko take fres=
h three inch diameter pugs of their coarse clay and throw a 30" high x 26" =
wide bowl. He later added the same 3" fresh pugs of clay to the rim which h=
ad been stiffened with a huge propane torch, and threw another 24" to the t=
op, making a 54" high Pith=C3=A1ria(storage jar) Oh and by the way, he used=
a sidesaddle kickwheel to throw the bottom piece. The yard outside was ful=
l of these large jars, fired and ready for shipment....... all of them made=
on a kickwheel.
>
> These fellows can kick some ass with clay, my friends!
>
> Cheers, Hank
>
>
>
>
> Niko and the kickwheel
>
>
>
>
> His buddy drying the rims
>
>
>
>
> Finished Pith=C3=A1ria, bottoms in the background. 25/day in Winter, 50/d=
ay in Summer.
| |
|
