[Clayart] re-firing

sumi sumi at herwheel.com
Wed Apr 27 03:11:46 UTC 2022


Where I used to teach I was in charge of firing for the china painting 
class. They used blank white fired china from a supplier, but often 
students would buy ware from thrift stores and paint on it. Usually, it 
was fine and made it through several firings with no trouble. Every now 
and then one of these second-hand pieces would break, but usually the 
very first time it was fired. Seemed like if it was solid, dense very 
white china, it was always fine. The pieces that broke were white, but 
had a different feel from the china blanks from the supplier. Restaurant 
supply china works well, too.

Sometimes they would paint on 12" square tiles and the safest way to get 
these through the firings was to stand them on edge leaning on kiln 
posts. Fired flat on a shelf they often broke but they made it through 
multiple firings on edge. Plates, too, could be fired on edge, often 
actually leaning on the wall of the kiln (not right on an element, of 

> Thanks to all for the information. After taking a China Painting class from
> Paul Lewing, I've been firing pieces about a half dozen times to cone 018
> or 014 on white ware that I've purchased from consignment stores. I
> wondered if this might compromise the finished pieces.
> Sharon
> 'What if?' Student
> Fort Worth, TX
> On Mon, Apr 25, 2022 at 9:30 PM <vpitelka at dtccom.net> wrote:
>> David Hendley gave a good answer.  To me, the most important consideration
>> is that maturation of clay and glazes depends on both temperature and
>> duration.  So if you glaze-fire again to the same cone, it is the like
>> increasing the duration of the firing beyond the normal maturation point.
>> Thus, you end up with slightly overfired wares, possibly over-vitrified,
>> more brittle, with lower thermal-shock-resistance, as David said.
>> A cone 8-11 claybody fired to cone-9 both times would stand up to refiring
>> just fine.  A cone 8-11 claybody fired to cone-11 both times would almost
>> certainly be over-vitrified.
>> - Vince
>> Vince Pitelka
>> Potter, Writer, Teacher
>> Chapel Hill, NC
>> vpitelka at dtccom.net
>> www.vincepitelka.com
>> https://chathamartistsguild.org/
>> -----Original Message-----
>> From: Clayart <clayart-bounces at lists.clayartworld.com> On Behalf Of Barry
>> Salaberry
>> Sent: Sunday, April 24, 2022 2:03 PM
>> To: clayart at lists.clayartworld.com
>> Subject: [Clayart] re-firing
>> Re-firing
>> I wonder if re-firing makes the pots more brittle that convention would
>> serve?
>> Would a dilatometer measurement of both provide less anecdotal survey?
>> Does cristobalite increase or decrease with that re-fire?
>> Is the pot which has been re-fired more subject to thermal shock?
>> Does it affect glaze fit?
>> Questions surface when we enter a new cave, but light does provide clarity
>> one hopes.
>> --
>> Barry Salaberry
>> "Hope is the thing with feathers
>> That perches in the soul
>> And sings tunes without the words
>> And never stops - at all!"
>>                        -Emily Dickinson
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