Diane Woloshyn on mon 31 jan 00
Went to use some glaze that I had been using for some time and discovered
that one of the chemicals had precipitated out on the bottom. It formed a
clear, crytalline film that looked like ice. It had been cold here, but not
that cold. Tried sieving that precipitate but it did not go throught the
sieve very well at all. Then put what I could get of the precipitate into
the blender with some of the rest of the glaze and that did the trick. Does
anyone have any idea what the precipitate could be and what caused it. I ran
a test piece and the glaze still has the same properties as before, inspite
of not getting all the precipitate back in the glaze.
This is the formula:
Falls Creek Shino
Albany Slip 56.07
Gerstely Borate 18.69
Soda feldspar 9.35
Silica 9.35
Lithium carb 6.54
Superpax 9.35
Tin Oxide 4.67
Thanks for anything you can suggest.
Diane Florida Bird Lady
Cindy Strnad on tue 1 feb 00
Diane,
My best guess is that your precipitate came from some soluble chemicals
introduced with the Gerstley. Most folks consider soluble chemicals in a
glaze to be a source of trouble and this is one of the things that earned
our lamented Gerstly the pet name of Ghastly.
Glaze chemicals should ideally be suspended but not dissolved in a glaze.
Since yours works just fine without this unknown stuff, I suggest you throw
away the crystals. If you really want them back in solution, you can
dissolve them in hot water and add them back to the glaze, however, I've
read lots of stuff by people who worked really hard to get them out of the
glaze in the first place.
Cindy Strnad
earthenv@gwtc.net
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
Abbey of New Clairvaux on tue 1 feb 00
Dear Diane,
I suspect it is the Lithium. I have a glaze that forms crystals when it
gets down to about 45 degrees. What I ended up doing was putting that glaze
in a place where it stayed warm. Another things I have done is strain the
glaze and put the crystals in a microwave and heat it up. They melt and
then I put it all back in the glaze. I have no knowledge of what this is
about, but just thought it interesting that your glaze and mine have
lithium. In my case, the crystals are on the surface.
Hope this is of some help.
Fr. Anthony
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.UKY.EDU]On Behalf
Of Diane Woloshyn
Sent: Monday, January 31, 2000 11:51 AM
To: CLAYART@LSV.UKY.EDU
Subject: Glaze precipitate
----------------------------Original message----------------------------
Went to use some glaze that I had been using for some time and discovered
that one of the chemicals had precipitated out on the bottom. It formed a
clear, crytalline film that looked like ice. It had been cold here, but not
that cold. Tried sieving that precipitate but it did not go throught the
sieve very well at all. Then put what I could get of the precipitate into
the blender with some of the rest of the glaze and that did the trick. Does
anyone have any idea what the precipitate could be and what caused it. I
ran
a test piece and the glaze still has the same properties as before, inspite
of not getting all the precipitate back in the glaze.
This is the formula:
Falls Creek Shino
Albany Slip 56.07
Gerstely Borate 18.69
Soda feldspar 9.35
Silica 9.35
Lithium carb 6.54
Superpax 9.35
Tin Oxide 4.67
Thanks for anything you can suggest.
Diane Florida Bird Lady
Ron Roy on wed 2 feb 00
Hi Diane,
I suggest an experiment - mix two versions of the glaze - one
without the lithium and one without the G Borate - just 200 grams.
These are the two solubles in your recipe. Keep em warm for a few
days - then keep em cold for a week and check to see of any crystals
are forming (this might need more time) - if the crystals are the
result of the two semi soluble materials then we can eliminate one -
particularly the GB because it will be the easiest to replace.
I suggest reforming to get the GB out anyway - which Ferro frits can you get?
RR
>----------------------------Original message----------------------------
>Went to use some glaze that I had been using for some time and discovered
>that one of the chemicals had precipitated out on the bottom. It formed a
>clear, crytalline film that looked like ice. It had been cold here, but not
>that cold. Tried sieving that precipitate but it did not go throught the
>sieve very well at all. Then put what I could get of the precipitate into
>the blender with some of the rest of the glaze and that did the trick. Does
>anyone have any idea what the precipitate could be and what caused it. I ran
>a test piece and the glaze still has the same properties as before, inspite
>of not getting all the precipitate back in the glaze.
>This is the formula:
>
>Falls Creek Shino
>
>Albany Slip 56.07
>Gerstely Borate 18.69
>Soda feldspar 9.35
>Silica 9.35
>Lithium carb 6.54
>Superpax 9.35
>Tin Oxide 4.67
>
>
>Thanks for anything you can suggest.
>
>Diane Florida Bird Lady
Ron Roy
93 Pegasus Trail,
Scarborough, Ontario
Canada. M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
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