Karen and Cliff Sandlin on fri 24 nov 00
I was trying to match a pottery studio piece I made with a "glaze" of =
1/2 copper carbonate and 1/2 gherstley borate, followed by a clear coat =
(on low fire clay) fired at Cone 04. the finish was a beautiful "runny" =
metallic blue/green with the claybody showing through.
I made a glaze of 1/2 GB & CC & water and another "glaze" of 1/2 Laguna =
Borate (as a GB substitute), 1/2 Copper Carb & water.
I applied each glaze on 3 pieces -- 2 coats and 1 coat Amaco Low-fire =
Clear glaze. However, I used Laguna Cone 5-6 clay.
All ended up with a grey metallic finish that ran onto the kiln shelves =
and required chipping out when I fired at a slow speed Cone 04.
Did I use:
-too much CC?
-too thick of a glaze, ie. not enough water?
-wrong clay?
-wrong speed? (Skutt automatic kiln--electric)
Is Laguna Borate not a good substitute for gherstley borate? Does =
anyone know a better substitute?
I have only had my kiln a few months and hope these are not stupid =
questions. Thanks.
Karen
Frank Gaydos on fri 24 nov 00
Karen,
As I understand it, there is not going to be a direct substitute for GB. You
will need to test, test, test.
Always do testing on test tiles , using the clay you will be working with.
Never use your work as a test tile. The reason your Laguna is rated at cone
5-6 is because that is the temperature it matures at. At cone 04 it is still
bisque ware. Not mature. Though I doubt this is the reason for the meltdown.
All clay and glazes interact with each other during the firing. That is why
a glaze looks wonderful on one body and ugly on another.
When you test you need to reproduce as near as possible the original setup
and keep variables to a minimum.
Frank Gaydos
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Subject: What did I do wrong? Laguna Borate?
I was trying to match a pottery studio piece I made with a "glaze" of 1/2
copper carbonate and 1/2 gherstley borate, followed by a clear coat (on low
fire clay) fired at Cone 04. the finish was a beautiful "runny" metallic
blue/green with the claybody showing through.
I made a glaze of 1/2 GB & CC & water and another "glaze" of 1/2 Laguna
Borate (as a GB substitute), 1/2 Copper Carb & water.
I applied each glaze on 3 pieces -- 2 coats and 1 coat Amaco Low-fire Clear
glaze. However, I used Laguna Cone 5-6 clay.
All ended up with a grey metallic finish that ran onto the kiln shelves and
required chipping out when I fired at a slow speed Cone 04.
Did I use:
-too much CC?
-too thick of a glaze, ie. not enough water?
-wrong clay?
-wrong speed? (Skutt automatic kiln--electric)
Is Laguna Borate not a good substitute for gherstley borate? Does anyone
know a better substitute?
I have only had my kiln a few months and hope these are not stupid
questions. Thanks.
Karen
Gabrielle on sun 26 nov 00
Hi Karen,
I don't have a vast amount of experience, but I would say that 50%
copper carb. to 50% of any glaze would be very runny. I think because
the copper carb. acts luck a flux. Now on the other hand, if you took
this same mixture but added enough water so that the solution was
like, perhaps milk, or a little thicker then it wouldn't run off the
pot and would be just fine. I haven't tried the Laguna Borate, but
I'm sure with some testing it may work very well.
Good luck testing!
g.
--- In clayart@egroups.com, Karen and Cliff Sandlin
wrote:
I was trying to match a pottery studio piece I made with a "glaze" of
1/2 copper carbonate and 1/2 gherstley borate, followed by a clear
coat (on low fire clay) fired at Cone 04. the finish was a
beautiful "runny" metallic blue/green with the claybody showing
through.
I made a glaze of 1/2 GB & CC & water and another "glaze" of 1/2
Laguna Borate (as a GB substitute), 1/2 Copper Carb & water.
I applied each glaze on 3 pieces -- 2 coats and 1 coat Amaco Low-fire
Clear glaze. However, I used Laguna Cone 5-6 clay.
All ended up with a grey metallic finish that ran onto the kiln
shelves and required chipping out when I fired at a slow speed Cone
04.
Did I use:
-too much CC?
-too thick of a glaze, ie. not enough water?
-wrong clay?
-wrong speed? (Skutt automatic kiln--electric)
Is Laguna Borate not a good substitute for gherstley borate? Does
anyone know a better substitute?
I have only had my kiln a few months and hope these are not stupid
questions. Thanks.
Karen
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