June Perry on wed 13 nov 02
I don't think the crystals are causing the crazing. You're getting crystals,
I think, because of the materials in the glaze, the goodly amount of silica
and your firing down which is encouraging crystal growth. You have calcium,
magnesium and lithium in there -- all of which will potentially give crystal
growth in a slow cooling/firing down schedule that you mentioned.
I have some high calcium matts that can go satin in normal firing but become
a gorgeous true matt when fired down, because it gives those crystals from
the calcium time to form.
You might want to try a little test 1-200 gram batch lowering the silica to
22 as I mentioned, to see what possible difference it might make in the
crazing and/or the crystal growth.
Regards,
June Perry
http://www.angelfire.com/art2/shambhalapottery/index.html
Carol Tripp on wed 13 nov 02
Hi June,
Actually the first Tenmoku Gold recipe I tried had way way lower silica; it
ran but had spikey gold crystals on a brown glossy surface. Then Cindy
Strnad posted a revised recipe which is the 7.07 CoE one with 21 silica and
that crazed. And it had more crystals, closer together. I step by step
kept raising the silica and saw the crystal field become denser but the
crazing never went away. As for the fire down, I think other people use the
Tenmoku Gold and get crystals without any special slow cool. They get a
surface looking like a starry sky, not a calcium matt. Personally, I'm
looking for the stars. (And the sun and the moon while I am at it.)
Thanks for taking the time to discuss this.
Best regards,
Carol
Dubai, UAE
June wrote:
>I don't think the crystals are causing the crazing. You're getting
>crystals,
>I think, because of the materials in the glaze, the goodly amount of silica
>and your firing down which is encouraging crystal growth. You have calcium,
>magnesium and lithium in there -- all of which will potentially give
>crystal
>growth in a slow cooling/firing down schedule that you mentioned.
>I have some high calcium matts that can go satin in normal firing but
>become
>a gorgeous true matt when fired down, because it gives those crystals from
>the calcium time to form.
>You might want to try a little test 1-200 gram batch lowering the silica to
>22 as I mentioned, to see what possible difference it might make in the
>crazing and/or the crystal growth.
>
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Joan Ashworth on thu 14 nov 02
Carol
I have been using Cindy Strnad's Ten Gold recipe, with local ingredients. It
works like a dream - small gold speckles (crystals) in a dark brown glossy
background.
If I soak it, or cool slowly, the gold crystals increase, and gradually join
together to form a matt, golden yellow cover. On one pot, the brown
disappeared entirely.
The thicker the glaze the more crystals.
It's an extremely reliable glaze,and, for some reason, improves as it ages
in the bucket.
Joan
in Durban South Africa
Gail Dapogny on thu 14 nov 02
Joan,
Would you care to pass it on to us along with firing temp and atmosphere?
Sounds like a lovely glaze, worth fooling around with. Thanks --- Gail
Dapogny
>
>I have been using Cindy Strnad's Ten Gold recipe, with local ingredients. It
>works like a dream - small gold speckles (crystals) in a dark brown glossy
>background.
>If I soak it, or cool slowly, the gold crystals increase, and gradually join
>together to form a matt, golden yellow cover. On one pot, the brown
>disappeared entirely.
>The thicker the glaze the more crystals.
>
>It's an extremely reliable glaze,and, for some reason, improves as it ages
>in the bucket.
>
>Joan
Carol Tripp on thu 14 nov 02
Hi Joan,
I would be interested to know if you converted Cindy's recipe using a
program, or did you "seat of the pants it"? Why I'd want to know is, does
your Tenmoku Gold craze and how does the analysis of it compare to Cindy's?
I had burned out on testing this glaze but now I am back into it and ready
to test test test all over again. (That is, when the tummy bug residing in
my son leaves.)
I almost forgot: when you layer this glaze over another one, do you find
that it dries crazed and barely hangs on but when it fires, everything
smooths out and looks great?
Best regards,
Carol
Dubai, UAE
Joan wrote:
>
>I have been using Cindy Strnad's Ten Gold recipe, with local ingredients.
>It
>works like a dream - small gold speckles (crystals) in a dark brown glossy
>background.
>If I soak it, or cool slowly, the gold crystals increase, and gradually
>join
>together to form a matt, golden yellow cover. On one pot, the brown
>disappeared entirely.
>The thicker the glaze the more crystals.
>
>It's an extremely reliable glaze,and, for some reason, improves as it ages
>in the bucket.
>
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Joan Ashworth on sat 16 nov 02
Hi Carol
Although I have the Insight program, I soon discovered that without the
analyses of the frits and clays that are available here (makers will not
release the analyses), I was pretty much in the dark when in comes to
working with formulae. So I work with the recipes, without any adjustment at
all. This is true for both recipes generous clayarters share and those I
discover in books.
I have the analysis of the local kaolin (G1), and have seen it is higher in
silica than most of the American kaolins. I guess this might affect the
crazing factor? I do not pursue a recipe if it does not work - there are so
many to choose from, I just roll onto the next.
To return to Cindi's Tenmoku Gold - it worked from day one, with a plethora
of gold speckling. No crazing. I sent a mail to Cindi to thank her for the
glaze recipe, and in her reply she said she was having some trouble with it,
as the gold speckling was often missing.
I haven't tried layering this glaze, but will do so. Thanks so much for the
idea. I wonder if the lack of crazing and large number of microcrystals
that form is due to the extra silica in the kaolin? Only the glaze gurus
would know.
Joan
in Durban
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