Teresa Wooden on tue 20 feb 07
We make most of our own glazes based on the recipes in MC6G. I have tried
Coyote glazes and was very pleased with the results. However... I used
their Sage Green on the outide of some mugs with MC6G Bone on the inside.
Looked great. No crazing, no apparent problems. Then we found that when
hot coffee was poured into the mugs (which were at room temperature) the
bottoms just shattered out in one loud CRACK! Hot coffee all down your
front. The expansion characteristics were so different that the mug was
virtually pulled apart.
We contacted Coyote and they said that Sage Green was one of their Shino
glazes and had a rather low expansion rate (which would incline a glaze
toward shivering, not crazing, I believe).
The problem here arose when combining glazes with very different expansion
rates. We know the expansion rates of the glazes that we make ourselves,
and are careful to try and match any new recipes so that they will all work
together, more or less. (We use Glazemaster calculation program.) We did
not ask Coyote for their COE for Sage Green... it seemed to us that unless
it was calculated on the same program it might be variable.
Moral of the story... torture test any new clays, glazes or glaze
combinations that you purchase or make! We now place new glazes in the
freezer for a few hours and then pour boiling water into the vessels (place
it safely down into a deep sink and maybe even wear protective
eyewear...). Amazingly, most of the MC6G based recipes fit our clay and
pass this horrific test. lol!
And then run out and buy product liability insurance, just in case! (Ours
is through Acuity. Very reasonable. Million dollar coverage.)
BTW, one Coyote glaze that does do well with our MC6G based glazes and our
clay is their Rust Brown. Very nice over texture, nice mat finish. We use
lots of it. It is Triple-T certified... Totally Torture Tested. :) But
do your own tests, to be sure.
Teresa Wooden
Lisa E on tue 20 feb 07
Hi Teresa;
I really appreciate your feedback because my existing glazes are MC6G and I
have bone and many others. I also love the Coyote Shino's and planned on
buying more (apparently they are coming out with 12 more). I will test like
crazy and most likely use their Shino's inside and out on items which will
come in contact with heat.
I wonder if the clay had anything to do with it? Hard to say but I will
take heed!
Regards,
Lisa Elbertsen
On 2/20/07, Teresa Wooden wrote:
>
> We make most of our own glazes based on the recipes in MC6G. I have tried
> Coyote glazes and was very pleased with the results. However... I used
> their Sage Green on the outide of some mugs with MC6G Bone on the inside.
> Looked great. No crazing, no apparent problems. Then we found that when
> hot coffee was poured into the mugs (which were at room temperature) the
> bottoms just shattered out in one loud CRACK! Hot coffee all down your
> front. The expansion characteristics were so different that the mug was
> virtually pulled apart.
>
> We contacted Coyote and they said that Sage Green was one of their Shino
> glazes and had a rather low expansion rate (which would incline a glaze
> toward shivering, not crazing, I believe).
>
> The problem here arose when combining glazes with very different expansion
> rates. We know the expansion rates of the glazes that we make ourselves,
> and are careful to try and match any new recipes so that they will all
> work
> together, more or less. (We use Glazemaster calculation program.) We did
> not ask Coyote for their COE for Sage Green... it seemed to us that unless
> it was calculated on the same program it might be variable.
>
> Moral of the story... torture test any new clays, glazes or glaze
> combinations that you purchase or make! We now place new glazes in the
> freezer for a few hours and then pour boiling water into the vessels
> (place
> it safely down into a deep sink and maybe even wear protective
> eyewear...). Amazingly, most of the MC6G based recipes fit our clay and
> pass this horrific test. lol!
>
> And then run out and buy product liability insurance, just in case! (Ours
> is through Acuity. Very reasonable. Million dollar coverage.)
>
> BTW, one Coyote glaze that does do well with our MC6G based glazes and our
> clay is their Rust Brown. Very nice over texture, nice mat finish. We
> use
> lots of it. It is Triple-T certified... Totally Torture Tested. :) But
> do your own tests, to be sure.
>
> Teresa Wooden
>
>
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--
Lisa E
Sunny Daze Design Pottery Studio
SunnyDazeDesign@gmail.com
Squamish, BC Canada
www.lisaelbertsen.com http://picasaweb.google.com/SunnyDazeDesign
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