Michael Wendt on thu 24 mar 05
Holly,
It is likely that the clay body formulation is wrong.
This can happen any time the clay is too coarse. Then you have a strange
mixture that is fluxed body with inclusions of large grog after firing.
To see if the clay is really the same, slake some of the dry body scrap and
wet it to a slurry, dry that and make a few pieces to test the glaze fit. If
the glazes still don't fir, find another supplier who will make the clay the
same each time.
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, Idaho 83501
USA
wendtpot@lewiston.com
www.wendtpottery.com
Holly Shaw on thu 24 mar 05
I'm a dedicated lurker, and although I've participated in the "at home
mug exchange", this is my first posting.
I have a problem I just can't seem to solve by researching so here
goes-
I use Byrne sandy white ^6 stoneware, no grog. It 's usually a nice
plastic smooth body that normally fits my glazes perfectly with no
problems. A few months ago I picked up 250 lb. from my local
supplier. There were small, course, grog-like inclusions that showed
up when trimming, causing drag marks. I called the supplier ,
informed them and was told that perhaps there was a 'clean-out-
between-batches' problem at the production facility. So I figured I'd
just live with it for now and the next batch would be normal. The next
batch of 250 lbs. also had the grit, I called again, this time they called
the production facility who said that this happens from time to time
and is a normal course of events when the prep machinery's grinding
apparatus is worn and is soon to be replaced. The inclusions are not
grog, but one of the primary ingredients in a too-coarse state. I was
told that no one else had complained, and they gave me 200 lbs. free.
I can live with the grit, but right about the time I got the first bad batch I
experienced shivering with one of my previously friendly glazes. The
glaze is a couple of years old so I thought maybe it had altered with
time. However my last kiln load showed shivering with more
'previously reliable' glazes, and major shivering on slipware with clear
overglaze. The slip is made from the same clay body and was applied
on leather hard pieces of the correct consistency.
So my questions are- what are the fundamental causes of shivering
and what is my most likely culprit? ( None of these glazes are new
batches, all were previously reliable.) Does any one else use this clay
and if so, have you experienced any problems?
I forgot to turn the fan vent off soon after reaching temperature this
last kiln,(to slow cooling) but didn't unload the kiln until it was well
below 150 F. Would the cool down effect the shivering?
I realize that shivering is fundamentally a fit problem where the glaze
is 'too big' for the clay but are there other factors?
I did extensive testing before initially settling on the Byrne, so now I'm
going back and re-examining those test pieces to find a suitable
replacement.
I'd appreciate any input, thanks!
Holly
Meadow Point Studios
CT.
Ron Roy on fri 25 mar 05
Hi Holly,
Who makes that clay?
If you want to send me the recipies of your glazes I can check them to see
if the expansion is on the low side.
ronroy@ca.inter.net
I suspect it is the clay however - there have been a few examples of clay
on the market with cristobalite in them. If you would like me to find out
if that is the problem you will need to make a sample and fire it so I can
measure the expansion in my dilatometer - and it will show if there is
cristibalite present.
RR
>So my questions are- what are the fundamental causes of shivering
>and what is my most likely culprit? ( None of these glazes are new
>batches, all were previously reliable.) Does any one else use this clay
>and if so, have you experienced any problems?
> I forgot to turn the fan vent off soon after reaching temperature this
>last kiln,(to slow cooling) but didn't unload the kiln until it was well
>below 150 F. Would the cool down effect the shivering?
> I realize that shivering is fundamentally a fit problem where the glaze
>is 'too big' for the clay but are there other factors?
>I did extensive testing before initially settling on the Byrne, so now I'm
>going back and re-examining those test pieces to find a suitable
>replacement.
>
>I'd appreciate any input, thanks!
>
>Holly
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Eleanora Eden on wed 30 mar 05
Holly,
It is likely that the clay body formulation is wrong.
This can happen any time the clay is too coarse. Then you have a strange
mixture that is fluxed body with inclusions of large grog after firing.
To see if the clay is really the same, slake some of the dry body scrap and
wet it to a slurry, dry that and make a few pieces to test the glaze fit. If
the glazes still don't fir, find another supplier who will make the clay the
same each time.
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, Idaho 83501
USA
wendtpot@lewiston.com
www.wendtpottery.com
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Jane Murray-Smith on thu 31 mar 05
Re: Shivering
Don't know if you have already adressed this, but..
I had a beautiful glaze that shivered on a clay body that has a high rate
of shrinkage...80% ball clay... as well as being a bit 'toothy'. Wonderful
clay to work with. I do have glazes that are fine on it....it was just the
wrong fit
----- Original Message -----
From: "Eleanora Eden"
To:
Sent: Wednesday, March 30, 2005 7:11 PM
Subject: Re: Shivering......
> Holly,
> It is likely that the clay body formulation is wrong.
> This can happen any time the clay is too coarse. Then you have a strange
> mixture that is fluxed body with inclusions of large grog after firing.
> To see if the clay is really the same, slake some of the dry body scrap
> and
> wet it to a slurry, dry that and make a few pieces to test the glaze fit.
> If
> the glazes still don't fir, find another supplier who will make the clay
> the
> same each time.
> Regards,
> Michael Wendt
> Wendt Pottery
> 2729 Clearwater Ave
> Lewiston, Idaho 83501
> USA
> wendtpot@lewiston.com
> www.wendtpottery.com
>
> ______________________________________________________________________________
> 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.
>
> ______________________________________________________________________________
> 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.
>
Linda Ferzoco on fri 1 apr 05
I'm confused. I've seen photos of Mel-san's clay body; it's groggy enough
to skin your knuckles, but those high iron glazes don't seem to shiver.
Someone please elucidate.
Thanks, Linda
On Wed, 30 Mar 2005 22:11:44 -0500, Eleanora Eden wrote:
>Holly,
>It is likely that the clay body formulation is wrong.
>This can happen any time the clay is too coarse. Then you have a strange
>mixture that is fluxed body with inclusions of large grog after firing.
>To see if the clay is really the same, slake some of the dry body scrap and
>wet it to a slurry, dry that and make a few pieces to test the glaze fit. If
>the glazes still don't fir, find another supplier who will make the clay the
>same each time.
>Regards,
>Michael Wendt
>Wendt Pottery
>2729 Clearwater Ave
>Lewiston, Idaho 83501
>USA
>wendtpot@lewiston.com
>www.wendtpottery.com
>
>______________________________________________________________________________
>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.
>
>______________________________________________________________________________
>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.
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