greenware and glazed in same firing

updated tue 24 sep 02

Martin Howard on thu 19 sep 02

On page 218 of Susan Peterson's "The Craft and Art of Clay" she writes:-
pieces; raw ware robs the glaze of oxygen.>

Have others found this to be true?
Is it likely to be true in an electric kiln with both bisque and glaze
firing to between cones 1 and 3?
The method seems to work for me, but perhaps my glazes would be different if
I separated out the ware into a bisque firing and a glaze firing.

Martin Howard
Webbs Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
01371 850 423
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
Updated 6th July 2002

Lily Krakowski on thu 19 sep 02

Someone--maybe Emmanuel Cooper--writes somewhere that there always is some
reduction in electric kilns because when "all that stuff" burns out it sucks
up the oxygen. Having said that, I have fired glaze and bisque in the same
kiln, keeping the bisque at the bottom, glaze on higher shelves, for fear of
blowups not oxygen larceny. All I can say is, try both ways, see what works
for you.




Martin Howard writes:

> On page 218 of Susan Peterson's "The Craft and Art of Clay" she writes:-
> > pieces; raw ware robs the glaze of oxygen.>
>
> Have others found this to be true?
> Is it likely to be true in an electric kiln with both bisque and glaze
> firing to between cones 1 and 3?
> The method seems to work for me, but perhaps my glazes would be different if
> I separated out the ware into a bisque firing and a glaze firing.
>
> Martin Howard
> Webbs Cottage Pottery
> Woolpits Road, Great Saling
> BRAINTREE, Essex CM7 5DZ
> 01371 850 423
> martin@webbscottage.co.uk
> http://www.webbscottage.co.uk
> Updated 6th July 2002
>
> ______________________________________________________________________________
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Lili Krakowski
P.O. Box #1
Constableville, N.Y.
(315) 942-5916/ 397-2389

Be of good courage....

Pat Southwood on thu 19 sep 02

Greenware and glazed work in the same firing, I was always taught this was a
big no no, as I expect all of us were. At the Ad. Ed. place I'm at we have
to do it to get the work through fast enough, it works fine on the bought in
opaque "woolies" looking glazes but good old Dora Billingtons transparent
(lead bi 85 cornish stone 15 ) comes out looking dreadfull, white,scabby
and scaly.
I assumed that it was due to the escaping gasses caused by the bisque, but I
dont understand why the other glazes are ok.
If the information is of any use to anyone else I have just discovered that
dora/trans will raw fire very nicely over keuper red.
Best Wishes
Pat
----- Original Message -----
From: "Martin Howard"
To:
Sent: Thursday, September 19, 2002 5:47 PM
Subject: Greenware and glazed in same firing


> On page 218 of Susan Peterson's "The Craft and Art of Clay" she writes:-
> > pieces; raw ware robs the glaze of oxygen.>
>
> Have others found this to be true?
> Is it likely to be true in an electric kiln with both bisque and glaze
> firing to between cones 1 and 3?
> The method seems to work for me, but perhaps my glazes would be different
if
> I separated out the ware into a bisque firing and a glaze firing.
>
> Martin Howard
> Webbs Cottage Pottery
> Woolpits Road, Great Saling
> BRAINTREE, Essex CM7 5DZ
> 01371 850 423
> martin@webbscottage.co.uk
> http://www.webbscottage.co.uk
> Updated 6th July 2002
>
>
____________________________________________________________________________
__
> 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.

Paul Lewing on thu 19 sep 02

on 9/19/02 1:00 PM, Lily Krakowski at mlkrakowski@CITLINK.NET wrote:

> Martin Howard writes:
>
>> On page 218 of Susan Peterson's "The Craft and Art of Clay" she writes:-
>> >> pieces; raw ware robs the glaze of oxygen.>
>>
>> Have others found this to be true?
>> Is it likely to be true in an electric kiln with both bisque and glaze
>> firing to between cones 1 and 3?

I think the reason she says this is that some glaze colors, notably low-fire
cadmium reds and yellows, will disappear with the slightest hint of
reduction in a firing. A few pieces of greenware in a glaze firing would be
enough to kill the cadmium reds. Martin, you may not have experienced this
because, if you fire to cone 1-3, you're already too high for straight
cadmium red glazes. And the new encapsulated cadmium stains are not
affected in the same way by reduction.
This is a good example of why you should always question any sentence in a
text book that contains the words "never" or "always". Often these
statements are made in such categorical terms because the writer doesn't
want to go into all the reasons and exceptions. When you see such a
statement, the reaction should be "Is it true that that's ALWAYS true?" and
"If so, WHY is that true?" and "If it doesn't work, HOW doesn't it work?".
A lot of good and original work has been done by finding those narrow
circumstances where "they" say it won't ever work, but when conditions are
just right, it does work.
Paul Lewing,
signing off for ten days to do some workshops and see some fall foliage in
New England, and hopefully take in a Boston Red Sox game at Fenway Park.

Martin Howard on fri 20 sep 02

Paul writes
enough to kill the cadmium reds. >

Now that does explain why some tests I did of apricot and reddish stains
came out very pale. Yes, something happens as the kiln gets to neutral or
even slight reduction, but if I can find a work around method, then I will
continue to bisque and glaze at the same temperatures.
The advantages outweigh any contras, for me, but perhaps not for some
others.

Always question any dogmatic statement whoever it comes from:-)

Martin Howard
Webbs Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
01371 850 423
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
Updated 6th July 2002