Lou Raye Nichol on mon 8 feb 10
I have a problem with another kind of crack that I'd like help on.
I throw feet on almost all my bowls - made in porcelain. I trim them to the
inside profile and then throw the foot. I make two basic shapes - one is
just a plain bowl with either a low or pedestal thrown foot. The other has
faceted sides with a fairly deep thrown foot. I occasionally get spiral
cracks on the bottom of the faceted bowls - never on the plain bowls. I
started keeping them under plastic for extended periods, but it is going to
crack it will do it anyway once the plastic is off.
What do you think?
Lou Raye Nichol
Lou Raye Nichol
Carbon Trapped Porcelain
919-303-5848
www.louraye.com
pots@louraye.com
Michael Wendt on mon 8 feb 10
Lou Raye,
Assuming you spiral wedge, do you stand the spiral up on
end?
If so,
try stack and slam wire wedging and orient the laminations
flat to the wheel head.
I never see the kind of cracking you describe when I do it
this way.
I think spiral wedging is at the root of a lot of cracking
mysteries since it does not make the clay moisture content
uniform unless it is done for quite a while, changing
orientation periodically.
Regards,
Michael Wendt
Lou Raye wrote:
I have a problem with another kind of crack that I'd like
help on.
I throw feet on almost all my bowls - made in porcelain. I
trim them to the
inside profile and then throw the foot. I make two basic
shapes - one is
just a plain bowl with either a low or pedestal thrown foot.
The other has
faceted sides with a fairly deep thrown foot. I occasionally
get spiral
cracks on the bottom of the faceted bowls - never on the
plain bowls. I
started keeping them under plastic for extended periods, but
it is going to
crack it will do it anyway once the plastic is off.
What do you think?
Lou Raye Nichol
Antoinette Badenhorst on mon 8 feb 10
Lou, you should check your timing from throwing the pieces to actually addi=
=3D
ng the thrown footrim. When your clay start shrinking, it shrinks overall i=
=3D
n all directions. With any round object one has to add rounded add-ons as q=
=3D
uickly as possible or else it might crack loose. I bet if you check the tim=
=3D
e between throwing and adding footrims on the rounded bowls and timing from=
=3D
throwing to adding footrims to the faceted pieces , it took longer before =
=3D
you add the later. =3DC2=3DA0I wonder if you ever get vertical cracks throu=
gh t=3D
he footrims?=3D20
My guess is that you spend the extra time to facet your bowl which is just =
=3D
enough time to "cancel" your opportunity to add the footrim without crackin=
=3D
g. I would suggest that you first add the footrim before you facet the bowl=
=3D
, thus shrinking the time from throwing to attaching.=3D20
Another possibility is that you "alter" the=3DC2=3DA0platelett layout=3DC2=
=3DA0 on =3D
the faceted pieces and then add "wheel oriented clay platelets" to that . I=
=3D
do not know if the footrims of your pieces do attach to the faceted parts =
=3D
of your bowl or not, but knowing (at least I think I know.....) "the logics=
=3D
" of particle orientation, this might be something to consider.=3D20
I hope this helps.=3D20
Antoinette Badenhorst=3D20
Lincolnshire, Illinois=3D20
----- Original Message -----=3D20
From: "Lou Raye Nichol" =3D20
To: Clayart@LSV.CERAMICS.ORG=3D20
Sent: Monday, February 8, 2010 6:58:20 AM GMT -06:00 US/Canada Central=3D20
Subject: Another kind of crack=3D20
I have a problem with another kind of crack that I'd like help on.=3D20
I throw feet on almost all my bowls - made in porcelain. I trim them to the=
=3D
=3D20
inside profile and then throw the foot. I make two basic shapes - one is=3D=
20
just a plain bowl with either a low or pedestal thrown foot. The other has=
=3D
=3D20
faceted sides with a fairly deep thrown foot. I occasionally get spiral=3D2=
0
cracks on the bottom of the faceted bowls - never on the plain bowls. I=3D2=
0
started keeping them under plastic for extended periods, but it is going to=
=3D
=3D20
crack it will do it anyway once the plastic is off.=3D20
What do you think?=3D20
Lou Raye Nichol=3D20
Lou Raye Nichol=3D20
Carbon Trapped Porcelain=3D20
919-303-5848=3D20
www.louraye.com=3D20
pots@louraye.com=3D20
Lis Allison on mon 8 feb 10
On Monday 08 February 2010, you wrote:
> Lou Raye,
> Assuming you spiral wedge, do you stand the spiral up on
> end?
Pah. I think spiral cracking is almost always due to too thick bottoms.
Not the centre or flat parts of the bottom, but the area where the bottom
transitions to the wall. If you think of a bowl as a 'U' shape, if the
sharp bends are too thick for the flat bottom, it will crack as it dries.
Throw some bowls, trim them, then wire them in half vertically. You'll see
what you need to correct.
Lis
--
Elisabeth Allison
Pine Ridge Studio
www.Pine-Ridge-Studio.blogspot.com
Birgit Wright on tue 9 feb 10
Hi=3D3B I have a friend who throws foot rings on his teapots. He leaves a v=
er=3D
y thick bottom and just lets the pot sit until the top starts to stiffen up=
=3D
enough to turn the whole thing over=3D2C when it is centered he can open a=
nd=3D
pull the thick bottom because it will still be quite soft. I know he make=
=3D
s hundreds of teapots=3D2C maybe thousands. Birgit Wright=3D20
=3D20
> Date: Mon=3D2C 8 Feb 2010 07:58:20 -0500
> From: louraye@BUSINESSCOACHINSTITUTE.COM
> Subject: Another kind of crack
> To: Clayart@LSV.CERAMICS.ORG
>=3D20
> I have a problem with another kind of crack that I'd like help on.
>=3D20
> I throw feet on almost all my bowls - made in porcelain. I trim them to t=
=3D
he
> inside profile and then throw the foot. I make two basic shapes - one is
> just a plain bowl with either a low or pedestal thrown foot. The other ha=
=3D
s
> faceted sides with a fairly deep thrown foot. I occasionally get spiral
> cracks on the bottom of the faceted bowls - never on the plain bowls. I
> started keeping them under plastic for extended periods=3D2C but it is go=
in=3D
g to
> crack it will do it anyway once the plastic is off.
>=3D20
> What do you think?
>=3D20
> Lou Raye Nichol
>=3D20
> Lou Raye Nichol
> Carbon Trapped Porcelain
> 919-303-5848
> www.louraye.com
> pots@louraye.com
=3D20
_________________________________________________________________
paul gerhold on tue 9 feb 10
Lou,
If you have a wheel that reverses easily try reversing the wheel direction
and the compressing the bottom working from the outside in. do this near
the end of your throwing, if possible, and you will never see another spira=
l
crack no matter how thick the bottom before trimming.
Paul
On Mon, Feb 8, 2010 at 7:58 AM, Lou Raye Nichol <
louraye@businesscoachinstitute.com> wrote:
> I have a problem with another kind of crack that I'd like help on.
>
> I throw feet on almost all my bowls - made in porcelain. I trim them to t=
he
> inside profile and then throw the foot. I make two basic shapes - one is
> just a plain bowl with either a low or pedestal thrown foot. The other ha=
s
> faceted sides with a fairly deep thrown foot. I occasionally get spiral
> cracks on the bottom of the faceted bowls - never on the plain bowls. I
> started keeping them under plastic for extended periods, but it is going =
to
> crack it will do it anyway once the plastic is off.
>
> What do you think?
>
> Lou Raye Nichol
>
> Lou Raye Nichol
> Carbon Trapped Porcelain
> 919-303-5848
> www.louraye.com
> pots@louraye.com
>
| |
|
