Ray Carlton on tue 4 aug 98
green celadon
wollastonite 18
dolomite 4
premium feldspar 35
kaolin 14
silica 200wq 33
iron oxide 2
hi all...above is the recipe for my green celadon. I am having a lot of
problems with pitting in this glaze. There will be on any piece, between 1
and 10 pits aproximately 1mm in diam [1/16"] going right down to the clay.
has anybody got any ideas. I have had little experience with
wollastonite,and am wondering if this material is likely to be the culprit.
I have looked at the theoretical formula and it is shown as eqal parts of
silica and calcium. Is there any other stuff in it ???. This is driving me
nuts :-#
thanks in advance for any help
cheers Ray Carlton
McMahons Creek Victoria Australia
name Cat Jarosz on tue 4 aug 98
Ray i dont know if this will help or not but I have a friend
that gets pitting problems with some of her glazes if she puts it into
reduction to early... no problems at 06 -04...the clay body is the
culprit, but I wont get into that here, hope this gives you some
clue as to how to go about solving the problem... just another angle to
look at... cat
Ron Roy on wed 5 aug 98
Hi Ray - I assume this is for cone 10 reduction. I do not have an analysis
for premium spar and I don't know what kaolin you use - I calculated with
G200 and EPK . It looks like a good glaze to me.
If you have a ball cly you use in glazes that may help - it could be the
pin holes are related to a slight case of crawing? I remember replacing the
the kaolin in my tenmoko with ball clay and have not had a crawl since.
I am thinking this may be a bisque firing problem - if you care to pass on
a general description of your clay body and how you fire your bisque and
glaze I can make a better guess.
If you send the analysis for your spar and kaolin I can do a better job. If
it is not the firing then we have to make that glaze flow a bit more to
help seal up the pin holes - I wonder of you have used any new supplies of
materials or clay just before this started to happen?
Bet we can make this glaze work just fine.
>----------------------------Original message----------------------------
>green celadon
>wollastonite 18
>dolomite 4
>premium feldspar 35
>kaolin 14
>silica 200wq 33
>iron oxide 2
>
>hi all...above is the recipe for my green celadon. I am having a lot of
>problems with pitting in this glaze. There will be on any piece, between 1
>and 10 pits aproximately 1mm in diam [1/16"] going right down to the clay.
>has anybody got any ideas. I have had little experience with
>wollastonite,and am wondering if this material is likely to be the culprit.
>I have looked at the theoretical formula and it is shown as eqal parts of
>silica and calcium. Is there any other stuff in it ???. This is driving me
>nuts :-#
>
>thanks in advance for any help
>cheers Ray Carlton
>
>McMahons Creek Victoria Australia
>
>
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
gwalker on thu 6 aug 98
I think Ron is right, Ray, when he suggests the problem could be in the
bisque. We find that most Aussie clays must be bisqued to over 1000
degrees Celsius to prevent pinholing in the gloss. Feeney's clays are
notorious for that.
Petalite can also be a problem. Good luck, mate!
I have a simpler green celadon glaze recipe you can have if you would
like me to post it. A bit too busy just at this moment to find it, but
will dig it out. Just let me know.
Geoff.
David Hewitt on fri 7 aug 98
In message , Ron Roy writes
>----------------------------Original message----------------------------
>Hi Ray - I assume this is for cone 10 reduction. I do not have an analysis
>for premium spar and I don't know what kaolin you use - I calculated with
>G200 and EPK . It looks like a good glaze to me.
>
>If you have a ball cly you use in glazes that may help - it could be the
>pin holes are related to a slight case of crawing? I remember replacing the
>the kaolin in my tenmoko with ball clay and have not had a crawl since.
>
>I am thinking this may be a bisque firing problem - if you care to pass on
>a general description of your clay body and how you fire your bisque and
>glaze I can make a better guess.
>
>If you send the analysis for your spar and kaolin I can do a better job. If
>it is not the firing then we have to make that glaze flow a bit more to
>help seal up the pin holes - I wonder of you have used any new supplies of
>materials or clay just before this started to happen?
>
Ron's last comment above, asking if you have used any new supplies of
materials or *clay*, is all too topical for me. I left it to the last
few kg of a buff stoneware that I use before reordering, only to find
that I had caught the summer holidays and it would a month before I
could get any. I was offered some of the nearest available and took it.
The result was pitting where none had been experienced before. To
underline most clearly that it was the clay I had some items in the old
material and some in the alternative going through together. They had
the same biscuit firing, dipped in the same glaze and glaze fired
together. There was a slight colour difference as well as the pitting.
I thought this recent experience of mine might be of interest only as I
am not suggesting that you go out and try alternative clays. I am sure
Ron is correct in suggesting that the glaze needs to be made more fluid
and I am sure that he will achieve this for you.
David
--
David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP6 1DQ, UK. Tel:- +44 (0) 1633 420647
Own Web site http://www.dhpot.demon.co.uk
IMC Web site http://digitalfire.com/education/people/hewitt.htm
Ray Carlton on fri 7 aug 98
would appreciate that geoff
thanks heaps
i reckon you could be rtight about the clay a good oxidising blast at 1000
might help even in the gloss cycle [???]
At 09:29 06/08/98 EDT, you wrote:
>----------------------------Original message----------------------------
>I think Ron is right, Ray, when he suggests the problem could be in the
>bisque. We find that most Aussie clays must be bisqued to over 1000
>degrees Celsius to prevent pinholing in the gloss. Feeney's clays are
>notorious for that.
>
>Petalite can also be a problem. Good luck, mate!
>
>I have a simpler green celadon glaze recipe you can have if you would
>like me to post it. A bit too busy just at this moment to find it, but
>will dig it out. Just let me know.
>
>Geoff.
>
cheers Ray Carlton
McMahons Creek Victoria Australia
Edouard Bastarache on sat 8 aug 98
Hello all,
here is a good green celadon recipe C/8-10R,
i have fired it for years on many different
clay bodies, and engobes, without a single glaze flaw.
It comes from my late friend ,Claude Laliberti(Quebec City):
CELADON VERT
Custer spar..............43.5
Silica.......................28.1
E.P.K......................10.3
Whiting....................18.1
100
Bentonite..................1.0
Red Iron Oxide..........1.7
Edouard Bastarache
edouardb@sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/~edouardb/
----------
> De : Ray Carlton
> A : CLAYART@LSV.UKY.EDU
> Objet : Re: pitting celadon [technical]
> Date : 7 ao{t, 1998 14:00
>
> ----------------------------Original message----------------------------
> would appreciate that geoff
>
> thanks heaps
>
> i reckon you could be rtight about the clay a good oxidising blast at
1000
> might help even in the gloss cycle [???]
>
> At 09:29 06/08/98 EDT, you wrote:
> >----------------------------Original message----------------------------
> >I think Ron is right, Ray, when he suggests the problem could be in the
> >bisque. We find that most Aussie clays must be bisqued to over 1000
> >degrees Celsius to prevent pinholing in the gloss. Feeney's clays are
> >notorious for that.
> >
> >Petalite can also be a problem. Good luck, mate!
> >
> >I have a simpler green celadon glaze recipe you can have if you would
> >like me to post it. A bit too busy just at this moment to find it, but
> >will dig it out. Just let me know.
> >
> >Geoff.
> >
> cheers Ray Carlton
>
> McMahons Creek Victoria Australia
>
>
hal mc whinnie on mon 10 aug 98
thought you would like to know that this is a variation on the classic
40-30-20-10 glaze of Leach.
it is really interesting to me to see how many thimnes this classic for a
cone 10 glazxe emerges.
hal
On Sat, 8 Aug 1998 13:32:10 EDT Edouard Bastarache
writes:
>----------------------------Original
>message----------------------------
>Hello all,
>here is a good green celadon recipe C/8-10R,
>i have fired it for years on many different
>clay bodies, and engobes, without a single glaze flaw.
>It comes from my late friend ,Claude Laliberti(Quebec City):
>
>CELADON VERT
>
>Custer spar..............43.5
>Silica.......................28.1
>E.P.K......................10.3
>Whiting....................18.1
> 100
>
>Bentonite..................1.0
>Red Iron Oxide..........1.7
>
>
>Edouard Bastarache
>edouardb@sorel-tracy.qc.ca
>http://www.sorel-tracy.qc.ca/~edouardb/
>
>----------
>> De : Ray Carlton
>> A : CLAYART@LSV.UKY.EDU
>> Objet : Re: pitting celadon [technical]
>> Date : 7 ao{t, 1998 14:00
>>
>> ----------------------------Original
>message----------------------------
>> would appreciate that geoff
>>
>> thanks heaps
>>
>> i reckon you could be rtight about the clay a good oxidising blast
>at
>1000
>> might help even in the gloss cycle [???]
>>
>> At 09:29 06/08/98 EDT, you wrote:
>> >----------------------------Original
>message----------------------------
>> >I think Ron is right, Ray, when he suggests the problem could be in
>the
>> >bisque. We find that most Aussie clays must be bisqued to over 1000
>> >degrees Celsius to prevent pinholing in the gloss. Feeney's clays
>are
>> >notorious for that.
>> >
>> >Petalite can also be a problem. Good luck, mate!
>> >
>> >I have a simpler green celadon glaze recipe you can have if you
>would
>> >like me to post it. A bit too busy just at this moment to find it,
>but
>> >will dig it out. Just let me know.
>> >
>> >Geoff.
>> >
>> cheers Ray Carlton
>>
>> McMahons Creek Victoria Australia
>>
>>
>
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