Paul Herman on thu 6 feb 03
Saundra,
I have had this phenomenon happen, in the winter, in one of my glazes.
The glaze contained gerstley borate, no lithium. It disappeared when I
got the floor heat hooked up.
I was under the impression that they were sodium silicate crystals, but
can't remember where the impression came from. After straining them out,
the glaze behaved just fine.
best wishes,
Paul Herman
Great Basin Pottery
423-725 Scott Road
Doyle, California 96109 US
potter@psln.com
Saundra wrote:
> This afternoon I lifted the lid off my two gallon bucket of Pam Fredericks
> Glaze (Val Cushing's Workbook) and noticed about ten ~1 inch hexagonal,
> glassy crystals on the surface of the glaze, beneath a couple of inches of
> clear water. The glaze had been undisturbed for about two months. I then
> sieved the glaze and found about a cup more of 1 inch and smaller flat
> hexagons. The largest hexagon was about 1/2" thick.
>
> The ingredients in the glaze are nepheline syenite, gerstley borate,
> whiting, epk, flint and lithium carbonate. What could have crystallized
> out of the mix? Has anyone else found crystals in a glaze bucket?
>
> Saundra in Zirconia, NC
Dannon Rhudy on thu 6 feb 03
Saundra said:
Subject: Crystals in my glaze bucket?
> ...I lifted the lid off my two gallon bucket of ...Glaze ...and noticed
....hexagonal, glassy crystals on the surface of the glaze, ...then sieved
the glaze and found about a cup more of 1 inch and smaller flat hexagons.
.... >
Nephyline Syenite, Gerstley Borate, Lithium - all of these
are soluble to a greater or lesser degree. So some of the
chemicals you put in your original glaze are no longer there.
The glaze is altered, and may or may not fire to look similar
to the way it appeared previously.
Better test it before you fire your favorite pieces in it.
If you still have those crystals, you could try heating them
with some liquid in the microwave, and stir them back into
the glaze. It works for some things where crystals form.
regards
Dannon Rhudy
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jspoces on thu 6 feb 03
This afternoon I lifted the lid off my two gallon bucket of Pam Fredericks Glaze (Val Cushing's Workbook) and noticed about ten ~1 inch hexagonal, glassy crystals on the surface of the glaze, beneath a couple of inches of clear water. The glaze had been undisturbed for about two months. I then sieved the glaze and found about a cup more of 1 inch and smaller flat hexagons. The largest hexagon was about 1/2" thick.
The ingredients in the glaze are nepheline syenite, gerstley borate, whiting, epk, flint and lithium carbonate. What could have crystallized out of the mix? Has anyone else found crystals in a glaze bucket?
Saundra in Zirconia, NC
Sabine Wolf on fri 7 feb 03
> The ingredients in the glaze are nepheline syenite, gerstley borate,
whiting, epk, flint and lithium carbonate. What could have crystallized out
of the mix? Has anyone else found crystals in a glaze bucket?
It's the lithium carbonate, it crystallizes if you store the glaze under 15°
C. You can dissolve the crystals again with some heating of the glaze.
Sabine
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