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glaze shivering?

updated thu 22 may 03

 

ranmcc on sun 18 may 03


I tried a Cone 6 glaze on Standard 112 clay. Put it on a 7 inch vase. Got
some shivering at the bottom of the vase where it was thicker. Everywhere
else seemed to be fine. It went clear at the top rim of the vase but no
shivering there.

I got the formula off clayart archives. It is a nice glaze except for the
slight shivering. Can someone help me fix this glaze for this clay?

Cone 6 Roseville type glaze

Custer Feldspar 40.0
Frit 3124 9.0
Whiting 16.0
Talc 9.0
EPK 10.0
Flint/Silica 16.0
add Rutile 6.0
and
copper Carb 4.0

Randy
South Carolina

John Hesselberth on mon 19 may 03


Hi Randy,

I guess I have to ask what you mean by 'slight shivering'. Is the glaze
coming off in sharp slivers? Or is there a chance you are really
observing something that might be incipient crawling? This glaze is
well balanced and has an expansion coefficient that ought to fit many
cone 6 bodies. I have used Standard 112 in the past and saw nothing
out of the ordinary about it. If it really is shivering you are seeing
I would suggest that you might have an ingredients mix (an ingredient
that is not what it says it is on the bag)--like if your whiting were
really dolomite or, even worse, talc you might get into a shivering
situation--or, perhaps, you made a weighing error when you mixed up the
glaze.

Regards,

John

On Sunday, May 18, 2003, at 08:39 PM, ranmcc wrote:

> I got the formula off clayart archives. It is a nice glaze except for
> the
> slight shivering. Can someone help me fix this glaze for this clay?
>
http://www.frogpondpottery.com
http://www.masteringglazes.com

David Hewitt on mon 19 may 03


Randy

This recipe does not appear to have a very low CoE value, but if you are
getting shivering then it is too low for your clay.

I do not know the clay that you are using, but if you want to alter the
coefficient of expansion of the glaze by increasing it, than adding some
more whiting does this. What other changes it will make can only be
found out fully by testing.

Hope that this is of some help.

David
In message , ranmcc writes
>I tried a Cone 6 glaze on Standard 112 clay. Put it on a 7 inch vase. Got
>some shivering at the bottom of the vase where it was thicker. Everywhere
>else seemed to be fine. It went clear at the top rim of the vase but no
>shivering there.
>
>I got the formula off clayart archives. It is a nice glaze except for the
>slight shivering. Can someone help me fix this glaze for this clay?
>
>Cone 6 Roseville type glaze
>
>Custer Feldspar 40.0
>Frit 3124 9.0
>Whiting 16.0
>Talc 9.0
>EPK 10.0
>Flint/Silica 16.0
>add Rutile 6.0
>and
>copper Carb 4.0
>
>Randy
>South Carolina

--
David Hewitt
David Hewitt Pottery
7 Fairfield Road, Caerleon, Newport,
South Wales, NP18 3DQ.
Tel:- +44 (0) 1633 420647
Fax:- +44 (0) 870 1617274
Web:- http://www.dhpot.demon.co.uk

Fabienne Micheline Cassman on mon 19 may 03


Hello,

Sometimes I have noticed that a glaze as you describe it shivers where it is applied thick. Another though, if you hold a pot by the bottom while dipping it, you can leave oily finger marks where it will shiver.

Cheers,

Fabienne

>>I tried a Cone 6 glaze on Standard 112 clay. Put it on a 7 inch vase. Got
>>some shivering at the bottom of the vase where it was thicker.

--
Fabienne Cassman http://www.milkywayceramics.com/

WARNING: I cannot be held responsible for the above
because my cats have apparently learned to type.

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/_ \'. __..-' , ,--...--'''
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`-';' ; ; ;
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(,__....----''' (,..--''

--

ranmcc on tue 20 may 03


John this glaze appears to be actually crumbling away from the clay. No
sharp edges. Looks like the gas flame may have touched it. Possible
overfiring at the point where it is crumbling.


----- Original Message -----
From: "John Hesselberth"
To:
Sent: Monday, May 19, 2003 9:03 PM
Subject: Re: Glaze shivering?


> Hi Randy,
>
> I guess I have to ask what you mean by 'slight shivering'. Is the glaze
> coming off in sharp slivers? Or is there a chance you are really
> observing something that might be incipient crawling? This glaze is
> well balanced and has an expansion coefficient that ought to fit many
> cone 6 bodies. I have used Standard 112 in the past and saw nothing
> out of the ordinary about it. If it really is shivering you are seeing
> I would suggest that you might have an ingredients mix (an ingredient
> that is not what it says it is on the bag)--like if your whiting were
> really dolomite or, even worse, talc you might get into a shivering
> situation--or, perhaps, you made a weighing error when you mixed up the
> glaze.
>
> Regards,
>
> John
>
> On Sunday, May 18, 2003, at 08:39 PM, ranmcc wrote:
>
> > I got the formula off clayart archives. It is a nice glaze except for
> > the
> > slight shivering. Can someone help me fix this glaze for this clay?
> >
> http://www.frogpondpottery.com
> http://www.masteringglazes.com
>
>
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John Hesselberth on tue 20 may 03


On Tuesday, May 20, 2003, at 05:43 PM, ranmcc wrote:

> John this glaze appears to be actually crumbling away from the clay.
> No
> sharp edges. Looks like the gas flame may have touched it. Possible
> overfiring at the point where it is crumbling.

Hi Randy,

Maybe overfiring, but also possibly underfiring. It definitely doesn't
sound like shivering. I suggest underfiring because I went back and
looked at the unity formula more closely. Very little boron (.05).
Quite a bit of magnesium (.2). I am guessing this glaze needs a full
cone 6 to melt properly and might do better at cone 8 or so. Also when
you say the glaze is crumbling away from the pot, this sounds like it
never got fully melted. I know this isn't very definitive or helpful
but short of seeing your actual situation it's the best I can do. Does
anyone else have some ideas?

Regards,

John

http://www.frogpondpottery.com
http://www.masteringglazes.com
http://www.frogpondpottery.com
http://www.masteringglazes.com

Ron Roy on wed 21 may 03


Hi Randy,

Glaze looks OK expansion wise - not very often that I hear of this
happening at only the bottom. Remember - fast firing will often bring on
fit froblems because the glaze has not had enough heat work to bond
properly with the clay.

Could be - the bottom being thicker and on the shelf - the heating is being
held back.

Could it be you are using a sitter and you are firing fast. When that
happens the firing will be uneven. If that is the case slow the firing to
50C per hour for the end of the firing - and/or soak (hold temperature) as
you watch the cones go down.

It could also be under fired because you are not using a cone to calibrate
your sitter.

I need more info on this.

RR

>I tried a Cone 6 glaze on Standard 112 clay. Put it on a 7 inch vase. Got
>some shivering at the bottom of the vase where it was thicker. Everywhere
>else seemed to be fine. It went clear at the top rim of the vase but no
>shivering there.
>
>I got the formula off clayart archives. It is a nice glaze except for the
>slight shivering. Can someone help me fix this glaze for this clay?
>
>Cone 6 Roseville type glaze
>
>Custer Feldspar 40.0
>Frit 3124 9.0
>Whiting 16.0
>Talc 9.0
>EPK 10.0
>Flint/Silica 16.0
>add Rutile 6.0
>and
>copper Carb 4.0
>
>Randy

Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513

Carol Tripp on wed 21 may 03


I don't have any bright ideas to save this glaze batch BUT I can say that it
is the famous and well-loved Xavier's Warm Jade Green (pg 129 Val Cushing
Handbook) and without the rutile and copper, it's V.C. "71" Base (pg 122
same book). So...that should give some clue because this is a recipe that
works really well - at least I have never read any moans about it on
Clayart. Perhaps you have a mislabled bag of glaze chemicals or your scale
malfunctioned or you answered the phone while mixing...

This glaze should work and it is worth trying to get it right because it is
a great looking, strong, stable, functional glaze either fast cooled for a
glossy mint green or slow cooled to get thousands of silvery crystals on
mint green. It's also very nice with the infamous Floating Blue oxide
combo: cobalt carb !%, RIO 2% and rutile 4%. Oh, and if you mix up some soda
ash and hot water and drizzle some near the top of the pot on the outside,
you will get silver rivelets. Caution, this runs so stay near the top.
Good luck and keep trying.
Best regards,
Carol
Dubai, UAE

>On Tuesday, May 20, 2003, at 05:43 PM, ranmcc wrote:
>
>>John this glaze appears to be actually crumbling away from the clay.
>>No
>>sharp edges. Looks like the gas flame may have touched it. Possible
>>overfiring at the point where it is crumbling.
>
>John H wrote:>
>Maybe overfiring, but also possibly underfiring. It definitely doesn't
>sound like shivering. I suggest underfiring because I went back and
>looked at the unity formula more closely. Very little boron (.05).
>Quite a bit of magnesium (.2). I am guessing this glaze needs a full
>cone 6 to melt properly and might do better at cone 8 or so. Also when
>you say the glaze is crumbling away from the pot, this sounds like it
>never got fully melted. I know this isn't very definitive or helpful
>but short of seeing your actual situation it's the best I can do. Does
>anyone else have some ideas?
>
>Regards,
>
>John
>
>

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