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04 glaze bubbling

updated thu 31 oct 96

 

Jonathan Kirkendall on tue 15 oct 96

I am a confirmed and well-practiced cone 10 reduction firing kind of guy.
However, in the past year, I've been doing only 04 oxidation electric
firings, as I've moved and dont have access to a gas kiln. I have been
struggling trying to find an 04 clear for my earthenware pieces, and am
having a hard time. Two firings ago, though, I thought I had finally found
the clear of my dreams: no pinholes, no crazing, no bubbling. Today I opened
my kiln, and nothing but pots with bubbled glaze! SAME temperature (04) - I
can't figure it out. I did have a longer firing schedule (3 hours on low, 3
on medium, then high, instead of 2 hours on low and medium) because I had
some refires in there. Is the firing schedule the culprit? The glze recipe
is below:

NS 35
frit 3134 50
Ger. Borate 11.4
Wollastinite 7.2
EPK 2
ball clay 1

Any clues?
Jonathan in Yonkers, to whom every occupation other than potter is looking
good right about now.

Sue Davis on wed 16 oct 96

Hang in there! We all go through these trials & errors and an outside job
starts to look good. Then reality sets in and sense returns :-)

It sounds to me like your kiln over-fired the glaze. Try again doing the
firing the way you did it the first time.

Sue from Florida STILL working at pottery after a bout of "I'm going to get
an outside job" again. :-)

Eleanora Eden on fri 18 oct 96

We feel for you Jonathan!

About refires:

Ihave taken to doing separate refire kilns. You don't need to go as high
to remelt and I find that getting up to 1700 instead of 1875 (at cone 06)
and soaking for an hour does the trick primo style with no problems of
overfiring that I used to get. A small bit of newly applied glaze here
and there will melt in fine.

I would try an adapted form of this plan with afew of your pots which I
take it are overfired and see if a lower soak will calm them down.

Eleanora


Eleanora Eden 802 869-2003
Paradise Hill
Bellows Falls, VT 05101 eden@maple.sover.net

Robert Speirs, M.D. 766 X4450 on tue 22 oct 96

Hi Jonathan.

I've been meaning for a week to remember to bring my notebook home so I
could give you the recipe for a really good ^07-^03 clear glaze -
Worthington's Clear. I guess it is really well known because I found it
in my handouts at least in 3 different places. I have used it
successfully in the past at both 06 & 04. It seems really reliable.
Anyway, here it is and if you don't need it now, maybe in the future it
will be of use.

Worthington's Clear ^07-^03

Gerstley Borate 55
EPK 30
Flint l5

Good luck.

Laura

Bruce Johnson on wed 23 oct 96

>----------------------------Original message----------------------------
> Hi Jonathan.
>
> I've been meaning for a week to remember to bring my notebook home so I
> could give you the recipe for a really good ^07-^03 clear glaze -
> Worthington's Clear. I guess it is really well known because I found it
> in my handouts at least in 3 different places. I have used it
> successfully in the past at both 06 & 04. It seems really reliable.
> Anyway, here it is and if you don't need it now, maybe in the future it
> will be of use.
>
> Worthington's Clear ^07-^03
>
> Gerstley Borate 55
> EPK 30
> Flint l5
>
> Good luck.
>
> Laura
>
>Question for you Laura : I have used Worthington Clear but any glaze that I
use with that much Boran {GB} in it always seems to go a bluish, pinkish
color on my redware? Anyone? Bruce Madtown Wi