John Post on sat 7 aug 99
Ron Roy wrote...
>Has anyone else noticed how hard it is to adjust glazes with Gerstley
>Borate in them? I am constantly taking it out so I can get the results I
>want.
Ron I've had plenty of difficulty adjusting glazes with Gerstley in them.
I often like the way a glaze with Gerstley fires, but have problems with
the slurry turning to pudding in the bucket.
When I recalculate the glaze using frit 3134 as a substitute the fired
quality of the glaze changes. It leaves me wishing for a supplier who
would actually make a frit from the Gerstley itself instead of using Borax
as the source of B2O3 in the frit. I want a frit that has all of GB's
trace elements in it. These trace elements in the Gerstley seem to give it
some of its unique visual qualities when fired.
If I swap all of the GB for frit 3134 in a glaze, the glaze changes too
much. It's not that the new glaze isn't any good, it's just that it
doesn't often have the same opacity, coloration or mottling of the original
glaze.
My latest strategy has been to keep 10% or less Gerstley in the glaze and
replace the rest with 3134. This makes the slurry more manageable and it
still imparts some of GB's visual characteristics to the glaze. I find
that if I cross the 10% threshold in a glaze, the glaze starts to gel too
much.
It always amazes me when I see glazes posted on clayart that have 50%
Gerstley in them. In my experience with these types of glazes, I've had
the slurry turn into pudding in the bucket and then lead to crawling
problems in the firing.
I realize that in your posting you may be referring to the difficulty of
recalculating glazes with GB in them. I think this is directly related to
the strange and sometimes troublesome qualities of GB. Hence my wish for
a nice fritted version of the stuff...
regards...
John Post
Sterling Heights, Michigan
temmoku@actionwebs.net
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