Lee Love on thu 7 sep 06
Are your lids thinner than the thickness of the body? Does thickness
effect shrinkage?
--
Lee in Mashiko, Japan
http://potters.blogspot.com/
"Let the beauty we love be what we do." - Rumi
Fredrick Paget on thu 7 sep 06
Getting ready for the Wood Fire Conference, I threw a nice big pot -
about 3 gallon size and made a lid for it that, in the wet clay
stage, fit very nicely. After the bisque firing the lid is now a way
too small . It has over 1/2 inch of play.
It is made from the same bag of clay - a cone 10 stoneware that is
called Jepson clay by Axner. It was bisque fired with the lid on the
pot, on the top shelf of the electric kiln to cone 04.
I am wondering if there is some voodoo that I am missing about making lids.
--
Fred Paget,
Marin County, CA, USA
fredrick@well.com
Charter Member Potters Council
Lynn Goodman Porcelain Pottery on thu 7 sep 06
I always make my lids a little bit too wide because they shrink more
than the gallery they sit on, although the difference is less after
glaze firing. Your lid may also fit a bit better after the wood firing.
I think it has to do with the comparable size/thickness of the
different parts, and probably a difference in the amount of water
absorbed by the different parts (the lid is thinner, and therefore
absorbs relatively more water). After making a few lidded pieces, a
percentage of difference between parts should become apparent and more
predictable.
Lynn
On Sep 7, 2006, at 5:37 PM, Fredrick Paget wrote:
> Getting ready for the Wood Fire Conference, I threw a nice big pot -
> about 3 gallon size and made a lid for it that, in the wet clay
> stage, fit very nicely. After the bisque firing the lid is now a way
> too small . It has over 1/2 inch of play.
>
> It is made from the same bag of clay - a cone 10 stoneware that is
> called Jepson clay by Axner. It was bisque fired with the lid on the
> pot, on the top shelf of the electric kiln to cone 04.
>
> I am wondering if there is some voodoo that I am missing about making
> lids.
> --
> Fred Paget,
> Marin County, CA, USA
> fredrick@well.com
>
> Charter Member Potters Council
>
> _______________________________________________________________________
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> Send postings to clayart@lsv.ceramics.org
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>
>
Lynn Goodman
Fine Porcelain Pottery
548 Court St.
Brooklyn, NY 11231
718-858-6920
Cell 347-526-9805
www.lynngoodmanporcelain.com
jlutz on thu 7 sep 06
I have the same problem!! I've notices that flat lids shrink more
than rounded ones. The shrinkage increases from the bisque firing to
the glaze firing.
Is there some law of physics that I'm not aware of that causes
smaller, differently shaped pieces to shrink at different rates?
I've even tried making flat lids larger than needed to see if I could
come up with one that would eventually fit. Doesn't work.
Jean Lutz
Prescott, AZ
It's raining!!!
At 02:37 PM 9/7/2006, you wrote:
>Getting ready for the Wood Fire Conference, I threw a nice big pot -
>about 3 gallon size and made a lid for it that, in the wet clay
>stage, fit very nicely. After the bisque firing the lid is now a way
>too small . It has over 1/2 inch of play.
>
> It is made from the same bag of clay - a cone 10 stoneware that is
>called Jepson clay by Axner. It was bisque fired with the lid on the
>pot, on the top shelf of the electric kiln to cone 04.
>
>I am wondering if there is some voodoo that I am missing about making lids.
>--
> Fred Paget,
> Marin County, CA, USA
> fredrick@well.com
>
> Charter Member Potters Council
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
>melpots@pclink.com.
pdp1@EARTHLINK.NET on thu 7 sep 06
Hi Fred,
The only thing that comes to mind from my own
scant experience...
Is to measure exactly, when green and dry, the
galley OD of the inside of the ( in effect,
'test' ) Lid, before fireing.
Really, to measure that AND the ID of the Pot's
top opening the lid is to go on, in the same
manner.
Then, when the post fire fit is way off, or off
however much, one has a definite reference of the
actual shrinkange rate, from which to determine
what the 'new' Lid must be, when green and
dry..and to Trim accordingly.
This is what I would do anyway...
So, you may have to start over with this...or, at
least start over with a controll-test Lid to
determine it's actual shrinkage from the
fire...for this Pot to then have it's nicely
fitting lid.
And certainly, the larger these items may be, the
more such possible differential shrinkage may
occur in the respective forms of Lid, and Pot.
Different shaped Lids, will also have different
shrinkages of their OD, and hence galleys...so I
would expect consistancy only with the same Clay,
the same cone/heat work, and the same fireing
process of course, and, for things/Lids to be the
same shape...
Little Cannisters may be forgiving...but not large
Work...
Good luck..!
Phil
Las Vegas
----- Original Message -----
From: "Fredrick Paget"
> Getting ready for the Wood Fire Conference, I
threw a nice big pot -
> about 3 gallon size and made a lid for it that,
in the wet clay
> stage, fit very nicely. After the bisque firing
the lid is now a way
> too small . It has over 1/2 inch of play.
>
> It is made from the same bag of clay - a cone
10 stoneware that is
> called Jepson clay by Axner. It was bisque
fired with the lid on the
> pot, on the top shelf of the electric kiln to
cone 04.
>
> I am wondering if there is some voodoo that I am
missing about making lids.
> --
> Fred Paget,
Ron Roy on fri 8 sep 06
Hi Fred,
This could be simply that the lids are not "compressed" as much as the
gallery is.
When you throw a lit upright on the wheel head the outside clay gets
stretched - same as when you throw a plate. If you don't strongly
recompress the edge it wants to shrink more. Stretched clay always shrinks
more than compressed clay.
It's the same reason that plate rims pull up when drying - stretched clay
shrinking more then the unstretched clay.
I think the best way to get a real good fit for lids is to throw them
bigger (compressing the edge) - dry em right on the gallery - so they are
exactly the same dryness at trimming time - then trim em to fit exactly.
The dry them in the gallery to make sure everything stays round
Did I explain that in a way that is understandable?
RR
>At 02:37 PM 9/7/2006, you wrote:
>>Getting ready for the Wood Fire Conference, I threw a nice big pot -
>>about 3 gallon size and made a lid for it that, in the wet clay
>>stage, fit very nicely. After the bisque firing the lid is now a way
>>too small . It has over 1/2 inch of play.
>>
>> It is made from the same bag of clay - a cone 10 stoneware that is
>>called Jepson clay by Axner. It was bisque fired with the lid on the
>>pot, on the top shelf of the electric kiln to cone 04.
>>
>>I am wondering if there is some voodoo that I am missing about making lids.
>>--
>> Fred Paget,
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Dannon Rhudy on fri 8 sep 06
Very often the clay in the lid of a pot is thinner than
the pot itself. Especially flat lids have this tendency.
It's going to shrink differently, and won't
fit. Take care to make the lid and pot the same thickness,
the same wetness, and at the same time. Practice,
practice.
regards
Dannon Rhudy
William & Susan Schran User on fri 8 sep 06
On 9/7/06 8:47 PM, "Lynn Goodman Porcelain Pottery"
wrote:
> I think it has to do with the comparable size/thickness of the
> different parts, and probably a difference in the amount of water
> absorbed by the different parts (the lid is thinner, and therefore
> absorbs relatively more water).
May have a little to do with it, but I think more than water is the
orientation of the clay particles and how that affects shrinkage.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
William & Susan Schran User on fri 8 sep 06
On 9/8/06 2:35 AM, "Lee Love" wrote:
> Are your lids thinner than the thickness of the body? Does thickness
> effect shrinkage?
Ummm... My first thought would be no, the lid & body of the same clay would
shrink the same no matter what thickness.
But then the amount of water absorbed into the clay (mentioned in another
posting) may expand/contract more.
But I still think the orientation of the clay particles - vertical in the
walls, horizontal in the lid - plays a greater role in direction/how the
clay is shrinking.
I have nothing to prove this, just seems to make sense to me.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
Nancy Braches on fri 8 sep 06
This may not be the "right" way to make lids but I do measure very carefully as as soon as I finish throwing the pot, then I make the lid. I keep the measurements until the piece is through the final glaze stage, then if there is a problem, I throw another lid and hope it fits. I also measure the thickness of the pot itself and insure the lid is of the same thickness. I have found when I need to trim a lid, I seem to have more trouble with fit so I try to throw all my lids so I don't need to trim them except for the knob. Thinner for me seems to shrink more, so the same thickness has been important and has solved my older problems of lid fittings of my larger pieces.
Nancy
Hilltop Pottery
Dannon Rhudy wrote: Very often the clay in the lid of a pot is thinner than
the pot itself. Especially flat lids have this tendency.
It's going to shrink differently, and won't
fit. Take care to make the lid and pot the same thickness,
the same wetness, and at the same time. Practice,
practice.
regards
Dannon Rhudy
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Fredrick Paget on sat 9 sep 06
>On 9/7/06 8:47 PM, "Lynn Goodman Porcelain Pottery"
> wrote:
>
>> I think it has to do with the comparable size/thickness of the
>> different parts, and probably a difference in the amount of water
>> absorbed by the different parts (the lid is thinner, and therefore
>> absorbs relatively more water).
>
>May have a little to do with it, but I think more than water is the
>orientation of the clay particles and how that affects shrinkage.
>
>
>-- William "Bill" Schran
That could be it. I sort of hand built that lid as a purely thrown
lid was not coming out in four attempts. The gallery is about 8
inches in diameter.
I was trying to get a slight dome shape and kept getting it too high
- sort of bowl shaped. Since I had the last one to where it measured
right I fan dried it for a couple of hours on the slowly rotating
wheel . Then I cut off and saved the rim and discarded the bowl shape
(Actually I made a shallow bowl out of it).
Then I got a lump of the same clay I was using and made a round slab
out of it by the Chinese pounding method using the Chinese clay
beater/mallet that I got from Po.
(I have seen how they beat the clay into a slab when making Yixing
teapots and also on a much larger scale making garden planters of 5
gallon size.)
You beat the clay with the curved side of the mallet and it moves
outward. You finish off with the flat side of the mallet. I got a
nice slab about 1/4 inch thick and transferred it to a hump mold
mounted on the wheel.
I spun it up on the wheel and threw it down on to the curve of the
hump then with needle tool cut it round and fan dried it so i could
lift it off and transfer it to the flat bat with the rim on it after
scoring and slipping the edge threw it to fit down, made a knob for
the top.
It came out well and after drying to the same leather hard state as
the pot,fitted well, a tiny bit loose. Then after drying ,I fired the
lid and pot - Lid on_ to cone 04. That is when it shrank so the lid
is about 3/4 inch too small.
It must have been that beating the clay got that oriented the clay
particles so they shrank more. Also when beating a slab you can use
drier clay so the lid top clay may have been drier than the throwing
clay of the pot body, I really can't remember.
Fred
--
From Fred Paget,
Marin County, CA, USA
fredrick@well.com
Charter Member Potters Council
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