Stuart Nicholls on fri 8 nov 96
To be brief - When my thrown pots dry, a crack appears on the bottom.
This happens to about 75% of the time. My pots are cracking up and so am I.
I would greatly appreciate any advice.
Tamsin A. Whitehead on fri 8 nov 96
Hi Stuart! It sounds like you are not getting enough compression in the
base of your pots - there was an earlier thread about throwing lids off
the hump which covered the same thing. After you have centered and opened
the pot, but before raising the wall, run the ball of your thumb or a
finger, or a rubber rib, from the center of the base to the wall and back
again as the
wheel spins, pressing down firmly, but not too hard as you don't want to
thin the base, just compress it. Do this a number of times.
If the base is much thicker than the walls of a pot, this can also
create problems as they could dry at different rates. Also, make sure
that you have cut the base away from the bat before it starts to dry so
that the clay doesn't pull on the bat.
Hope this helps,
Tamsin
Nottingham, NH
USA
On Fri, 8 Nov 1996, Stuart Nicholls wrote:
> ----------------------------Original message----------------------------
> To be brief - When my thrown pots dry, a crack appears on the bottom.
> This happens to about 75% of the time. My pots are cracking up and so am I.
> I would greatly appreciate any advice.
>
Lori Wilkinson on fri 8 nov 96
At 08:48 AM 11/8/96 EST, you wrote:
>----------------------------Original message----------------------------
>To be brief - When my thrown pots dry, a crack appears on the bottom.
>This happens to about 75% of the time. My pots are cracking up and so am I.
>I would greatly appreciate any advice.
>
Stuart, have you made sure the bottom of your pots are packed or pressed
down? Do you keep the inside bottom free of water? If the bottom of your
pots are thicker do you dry them slowly? Just a few things to consider.
Lori Wilkinson in Roswell NM
Don Jung on fri 8 nov 96
Stuart Nicholls wrote:
>
> ----------------------------Original message----------------------------
> To be brief - When my thrown pots dry, a crack appears on the bottom.
> This happens to about 75% of the time. My pots are cracking up and so am I.
> I would greatly appreciate any advice.
A great many posts went on about this a while back and we've encountered
and corrected the problem ourselves. Solutions are:
- if you throw with a lot of water, use a sponge to take the water out
of the bottom frequently. Keeping the bottom wet weakens the clay in
that area.
- lack of compression...press and go over the bottom of the pot in both
directions. Since you are squeezing and pulling on the sides of the
pot, to even out the tension you need to squeeze or compress the bottom
in a similar manner.
I find that these 2 things will cure it. I assume that the thickness of
the sides and bottom are close, if not, you have to dry very slowly. One
other suggestion is that you can put a wad of clay down first then throw
your clay on and begin working. The wad is suppose to 'disturb' the
spiral tension created...but I have less stock in this tip, but up to
you.
hope this helps. Likely you'll get more hints and if more people repeat
the same hint, the more likely it is to work.
Don Jung
in Wet Vancouver BC
LBCLAY@aol.com on fri 8 nov 96
Hi,,,,
I hope this helps you,,,cuz years ago,,,,my pots were cracking (s cracks) on
the bottom and I know what it feels like,,,it went on and on and I did
everything,,less water,,,more pressure,,,etc... but i still kept getting the
cracks...
What solved the problem for me is this:
I wedge in a cone shape...if you do,,,notice on the flat side,,the little
cracks already there,,,well instead of putting the FLAT side on the wheel
head,,,,put the POINT side down,,,,then you are compressing on the top.....it
Worked for me!
Brian O'Neill on fri 8 nov 96
Stuart:
If the crack is a distinctive "S" shape, it's possible that you are
throwing with too much water or working the pot a bit too much and the clay
is getting over saturated at the base where the water accumulates. Try
keeping as much water out of the bottom of the pot while throwing and
definately sponge it out when you've finished the piece.
You don't mention how you get the pieces off the wheel, but if you use a
particular type of batt, try varying the material (plaster, particle board,
etc.) and be sure you cut the piece from the batt with a wire tool.
Last resort is to change your clay body.
Hope this helps,
Brian O'Neill
Nils Lou on fri 8 nov 96
I suggest that you center the clay on the wheel, wheel wedge once or
twice ending with a centered mass about as high as it is wide with a
slightly rounded top. --now! wire off and turn the clay upside down.
proceed to recenter and throw whatever. I don't think you will have any
more bottom cracks. NL
On Fri, 8 Nov 1996, Stuart Nicholls wrote:
> ----------------------------Original message----------------------------
> To be brief - When my thrown pots dry, a crack appears on the bottom.
> This happens to about 75% of the time. My pots are cracking up and so am I.
> I would greatly appreciate any advice.
>
Jo Anne Boyd on sat 9 nov 96
I'm sure you'll get this suggestion for your cracking pots many times. Be
careful of two things when trimming your wheel thrown pottery. First check
that your
pot's bottom is close in thickness to the pot's wall thickness (you can check
with
a straight pin to determine the thickness before and after you trim).
Second, be
sure your pot is not too dry before you trim. Too much "stress" on the
bottom of your wares can promote cracking (especially if the inside bottom is
not a consistent thickness).
If these suggestions don't work, try slowing down how quickly your pottery
dries.
If you reduce the rate of "shrinkage" you reduce the stress on your wares.
Terrance Lazaroff on tue 12 nov 96
Sounds like "S" cracks. Is so then you require more compression at the
inside base when throwing.
You can also try burnishing the base with a rubber rib after your trim.
Lastly be sure you are drying your pots slowly and that they are on newsprint
or some other material that will move during shrinkage.
Best regards
Terrance F. Lazaroff
St Hubert, Quebec, CANADA!!!!!
tecnobud on wed 26 aug 98
Hello, everyone, I've been quietly listening to all of you for the last
couple of months, but now I am prompted to join in. I never laughed so hard
as at those couple of chicken messages, and human ash stories. I am a
ceramist, a scupltor, not a potter, but If I was a potter I would fry some
chickens in my kiln, and save the ash to make a glaze to adorn a whole
series of mugs I'd call chicken-ash cups, for all of the weird people out
there who are scared to get their hands dirty!
Keep those stories rolling, they're a hoot! Have any funny stories about
cooking in a kiln?
We over-charred a turkey one time at UT San Antonio, must have hit about
cone 04 before we knew it!
Marty Yochum in beautiful Estes Park, CO, where it is almost fall.
Susan Cline on mon 7 jun 10
Cathi - I have made these on and off for some time, also thrown in one
piece. I've always had difficulty with cracking such as yours because
of uneven thickness: the spot on the base where the wall rises is
difficult (for me) to make the same thickness as the rest of the base,
or of the wall. I've dried them, quickly, slowly, incredibly slowly
and even more, and I lose about 50%. I usually have to do some very
careful and significant trimming to even out the thickness. Even then
it's a c@#$ shoot. I have better luck with a slightly groggy clay -
it seems to be a little more forgiving.
My 2 cents. YMMV
Sue Cline
Cincinnati, OH
On Jun 7, 2010, at 3:17 PM, Cathi Newlin wrote:
> I've been working on some little bird feeders thrown as one piece -
> sort
> of a hopper-on-a-plate thing.
> I threw them 3 days ago and have been lightly covering them to dry
> them
> more slowly to prevent warping.
> Lightly trimmed the bottoms, just to clean them up.
> All seemed to be going well, and last night was a very humid night
> here,
> so as everything seemed to be cheese hard and drying evenly (and
> without
> warping I might add), I left them uncovered last night.
> I have cracks this morning.
>
> I *think* its a drying issue, but perhaps its a throwing or
> compression
> issue?
> I have pics and a little more info here:
> http://squarepegarts.blogspot.com/2010/06/cracking-up.html
> And as always, I appreciate the insight I get from you all.
> Thanks...
>
> --
> Cathi Newlin, Angels Camp, Ca
> cathi@box49.com
> box49@caltel.com
> cathi@SquarePegArts.com
>
> -------------------------------
> The Square Peg
> http://www.squarepegarts.com
>
> California Boxers in Need:
> http://CaliforniaBoxer.org
Larry Kruzan on mon 7 jun 10
Hi Cathi,
I took a look at your pic and I suspect that it is a drying issue. I'd ask
you to cut one in half so that we can see a cross-section of the pot. That
will help us to understand the dynamics of where the stress may be coming
from.
Also I wonder if this is the first time you have tried this form? I make a
one piece flower pot that is very similar to your birdhouse. I have to be
very careful about how even the wall thickness is - or I have cracks right
where yours are.
On my flower pots, my problem area is the base of the pot which can
sometimes end up thick. The thinner dish part dries quicker than the pot an=
d
cracks around the pot base.
So if you can, cut one in half and shoot a pic for us to see if this is the
problem for you too.
Best Wishes,
Larry Kruzan
Lost Creek Pottery
www.lostcreekpottery.com
-----Original Message-----
From: Clayart [mailto:Clayart@LSV.CERAMICS.ORG] On Behalf Of Cathi Newlin
Sent: Monday, June 07, 2010 2:17 PM
To: Clayart@LSV.CERAMICS.ORG
Subject: Cracking Up
I've been working on some little bird feeders thrown as one piece - sort
of a hopper-on-a-plate thing.
I threw them 3 days ago and have been lightly covering them to dry them
more slowly to prevent warping.
Lightly trimmed the bottoms, just to clean them up.
All seemed to be going well, and last night was a very humid night here,
so as everything seemed to be cheese hard and drying evenly (and without
warping I might add), I left them uncovered last night.
I have cracks this morning.
I *think* its a drying issue, but perhaps its a throwing or compression
issue?
I have pics and a little more info here:
http://squarepegarts.blogspot.com/2010/06/cracking-up.html
And as always, I appreciate the insight I get from you all.
Thanks...
--
Cathi Newlin, Angels Camp, Ca
cathi@box49.com
box49@caltel.com
cathi@SquarePegArts.com
-------------------------------
The Square Peg
http://www.squarepegarts.com
California Boxers in Need:
http://CaliforniaBoxer.org
=3D=3D=3D=3D=3D=3D=3D
Email scanned by PC Tools - No viruses or spyware found.
(Email Guard: 7.0.0.18, Virus/Spyware Database: 6.15150)
http://www.pctools.com/
=3D=3D=3D=3D=3D=3D=3D
Cathi Newlin on mon 7 jun 10
I've been working on some little bird feeders thrown as one piece - sort
of a hopper-on-a-plate thing.
I threw them 3 days ago and have been lightly covering them to dry them
more slowly to prevent warping.
Lightly trimmed the bottoms, just to clean them up.
All seemed to be going well, and last night was a very humid night here,
so as everything seemed to be cheese hard and drying evenly (and without
warping I might add), I left them uncovered last night.
I have cracks this morning.
I *think* its a drying issue, but perhaps its a throwing or compression
issue?
I have pics and a little more info here:
http://squarepegarts.blogspot.com/2010/06/cracking-up.html
And as always, I appreciate the insight I get from you all.
Thanks...
--
Cathi Newlin, Angels Camp, Ca
cathi@box49.com
box49@caltel.com
cathi@SquarePegArts.com
-------------------------------
The Square Peg
http://www.squarepegarts.com
California Boxers in Need:
http://CaliforniaBoxer.org
William & Susan Schran User on mon 7 jun 10
On 6/7/10 3:17 PM, "Cathi Newlin" wrote:
> I *think* its a drying issue, but perhaps its a throwing or compression
> issue?
> I have pics and a little more info here:
> http://squarepegarts.blogspot.com/2010/06/cracking-up.html
> And as always, I appreciate the insight I get from you all.
Cracking issue probably a combination of drying too fast/unevenly and chang=
e
in thickness - thick/thin areas next to each other.
Take one of the cracked ones and saw it in half vertically and examine the
thickness of the bottom of the container wall compared to the thickness of
the bottom off the trough. I think you'll find the bottom of the trough
thinner and this area dried/shrank before the wall did.
If you can get these areas more even and to dry at the same rate, you might
avoid cracking.
If the clay you're using has cracked with other complicated forms, you migh=
t
consider a clay with more tooth.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
douglas fur on mon 7 jun 10
Cathi
My first thougt was "looks like the kind of crack you get from water left
standing in the bottom of a pot"
Second thought "The 'bottle' part of the feeder looks nicer than the plate.
Why not eliminate the plate by making the bottom of the bottle with a deep
trimmed foot with two holes on opposite sides in which you stick a dowel or
twig perch and thereby eliminate the plate and cracks in on swel foop?
DRB
Seola Creek
On Mon, Jun 7, 2010 at 12:17 PM, Cathi Newlin wrote:
> I've been working on some little bird feeders thrown as one piece - sort
> of a hopper-on-a-plate thing.
> I threw them 3 days ago and have been lightly covering them to dry them
> more slowly to prevent warping.
> Lightly trimmed the bottoms, just to clean them up.
> All seemed to be going well, and last night was a very humid night here,
> so as everything seemed to be cheese hard and drying evenly (and without
> warping I might add), I left them uncovered last night.
> I have cracks this morning.
>
> I *think* its a drying issue, but perhaps its a throwing or compression
> issue?
> I have pics and a little more info here:
> http://squarepegarts.blogspot.com/2010/06/cracking-up.html
> And as always, I appreciate the insight I get from you all.
> Thanks...
>
> --
> Cathi Newlin, Angels Camp, Ca
> cathi@box49.com
> box49@caltel.com
> cathi@SquarePegArts.com
>
> -------------------------------
> The Square Peg
> http://www.squarepegarts.com
>
> California Boxers in Need:
> http://CaliforniaBoxer.org
>
gayle bair on tue 8 jun 10
Hi Cathy and Sue,
I make some garden art pieces with similar bottoms.=3D20
Through trial and many errors I found curving the base virtually =3D
eliminated the cracking.
I cut them off the wheel and place them on hardiboard.
When leather hard enough to pick up I place them in clear tubs with a =3D
piece of hardiboard in the bottom and replace the lid.=3D20
See tubs at: =3D
http://www.sterilite.com/SelectProduct.html?id=3D3D587&ProductCategory=3D3D=
179=3D
§ion=3D3D1
This process also allows them to dry more evenly.
BTW I do not use groggy clay preferring B-Mix type or porcelain =3D
claybodies.
See a sample on my web site:
=3D
http://www.claybair.com/Gayle_Bair_Pottery_index/Pages/Flying_Teacups.html=
=3D
I hope this is helpful,=3D20
Gayle Bair
Bainbridge Island WA
Tucson AZ
gayle@claybair.com
www.claybair.com
On Jun 7, 2010, at 7:35 PM, Susan Cline wrote:
> Cathi - I have made these on and off for some time, also thrown in one
> piece. I've always had difficulty with cracking such as yours because
> of uneven thickness: the spot on the base where the wall rises is
> difficult (for me) to make the same thickness as the rest of the base,
> or of the wall. I've dried them, quickly, slowly, incredibly slowly
> and even more, and I lose about 50%. I usually have to do some very
> careful and significant trimming to even out the thickness. Even then
> it's a c@#$ shoot. I have better luck with a slightly groggy clay -
> it seems to be a little more forgiving.
>=3D20
> My 2 cents. YMMV
> Sue Cline
> Cincinnati, OH
> On Jun 7, 2010, at 3:17 PM, Cathi Newlin wrote:
>=3D20
>> I've been working on some little bird feeders thrown as one piece -
>> sort
>> of a hopper-on-a-plate thing.
>> I threw them 3 days ago and have been lightly covering them to dry
>> them
>> more slowly to prevent warping.
>> Lightly trimmed the bottoms, just to clean them up.
>> All seemed to be going well, and last night was a very humid night
>> here,
>> so as everything seemed to be cheese hard and drying evenly (and
>> without
>> warping I might add), I left them uncovered last night.
>> I have cracks this morning.
>>=3D20
>> I *think* its a drying issue, but perhaps its a throwing or
>> compression
>> issue?
>> I have pics and a little more info here:
>> http://squarepegarts.blogspot.com/2010/06/cracking-up.html
>> And as always, I appreciate the insight I get from you all.
>> Thanks...
>>=3D20
>> --
>> Cathi Newlin, Angels Camp, Ca
>> cathi@box49.com
>> box49@caltel.com
>> cathi@SquarePegArts.com
>>=3D20
>> -------------------------------
>> The Square Peg
>> http://www.squarepegarts.com
>>=3D20
>> California Boxers in Need:
>> http://CaliforniaBoxer.org
| |
|
