Craig Martell on thu 30 mar 06
Hi again:
I've been curious about the other blue celadons that are more blue than
green but are still greener than the sky blue celadons that you can make
with high potassium glazes. So, I've done some tests. I know, "Get a life!"
I looked at a nice Yingqing celadon that Margaret Frith uses and I
calculated the formula. Then I converted this formula into a glaze recipe
that I could make with raw materials available here in the US. I also
calculated another Yingqing celadon from a percentage analysis in Nigel
Woods book on Chinese glazes. I placed 3 tests of each in different parts
of the kiln and fired them to cone 10 reduction.
Although the melt and surface texture was somewhat different, both glazes
produced the same light blue green color. Both glazes are very alkaline
and the common factor between the two is a high calcium
content. Margaret's glaze is 0.88 CaO and the recipe that I made from the
old Yingqing analysis is 0.81 CaO. Both glazes have a lower silica/alumina
ratio than the potassium sky blue glazes but not too low. Not
surprising. Many of the old Chinese glazes were made from porcelain stone
that was fluxed with limestone.
Application of these glazes is very important. They need to be pretty
thick to get the nice color. Claybody is a factor too and a very white
porcelain shows the best color in my opinion. I did some Chun tests too
and got some nice results and the application for the Chuns is a big factor
also. The Chuns were made with soda spar, fruitwood ash, grolleg and
quartz. They had a different makeup than the blue celadons but the blue in
the chuns comes from light scattering and not a solution color like the
celadons.
As far as which of these glazes is the "best", damned if I know. They are
all quite nice and it just depends on what you want and who's eyeballing them.
That's about it. There's a lot more to this but I don't want to hog all
the Clayart space. Pictures at eleven!
regards, Craig Martell Hopewell, Oregon
ilene mahler on fri 31 mar 06
Craig and Kathleen Gordon are either of you left handed as I will be
throwing your teabowls...Ilene
----- Original Message -----
From: "Craig Martell"
To:
Sent: Thursday, March 30, 2006 11:17 PM
Subject: The other blue celadon
> Hi again:
>
> I've been curious about the other blue celadons that are more blue than
> green but are still greener than the sky blue celadons that you can make
> with high potassium glazes. So, I've done some tests. I know, "Get a
> life!"
>
> I looked at a nice Yingqing celadon that Margaret Frith uses and I
> calculated the formula. Then I converted this formula into a glaze recipe
> that I could make with raw materials available here in the US. I also
> calculated another Yingqing celadon from a percentage analysis in Nigel
> Woods book on Chinese glazes. I placed 3 tests of each in different parts
> of the kiln and fired them to cone 10 reduction.
>
> Although the melt and surface texture was somewhat different, both glazes
> produced the same light blue green color. Both glazes are very alkaline
> and the common factor between the two is a high calcium
> content. Margaret's glaze is 0.88 CaO and the recipe that I made from the
> old Yingqing analysis is 0.81 CaO. Both glazes have a lower
> silica/alumina
> ratio than the potassium sky blue glazes but not too low. Not
> surprising. Many of the old Chinese glazes were made from porcelain stone
> that was fluxed with limestone.
>
> Application of these glazes is very important. They need to be pretty
> thick to get the nice color. Claybody is a factor too and a very white
> porcelain shows the best color in my opinion. I did some Chun tests too
> and got some nice results and the application for the Chuns is a big
> factor
> also. The Chuns were made with soda spar, fruitwood ash, grolleg and
> quartz. They had a different makeup than the blue celadons but the blue
> in
> the chuns comes from light scattering and not a solution color like the
> celadons.
>
> As far as which of these glazes is the "best", damned if I know. They are
> all quite nice and it just depends on what you want and who's eyeballing
> them.
>
> That's about it. There's a lot more to this but I don't want to hog all
> the Clayart space. Pictures at eleven!
>
> regards, Craig Martell Hopewell, Oregon
>
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>
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>
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> melpots@pclink.com.
Hank Murrow on fri 31 mar 06
On Mar 30, 2006, at 8:17 PM, Craig Martell wrote:
> Many of the old Chinese glazes were made from porcelain stone
> that was fluxed with limestone.
>
> Application of these glazes is very important. They need to be pretty
> thick to get the nice color. Claybody is a factor too and a very white
> porcelain shows the best color in my opinion.
Dear Craig;
I brought some porcelain-stone bowls into the Clayart room at the Red
Lion made by David Stannard from altered Rhyolites originating near
Fairbanks AK. The Rhyolite deposit is nearly iron and titanium free,
and its alkali content is mostly K2O. The bowls made from this body are
glazed with the Rhyolite body itself plus 20% Limestone, also from
Fairbanks. They are blue when fired in reduction (white satin in
oxidation) and ring like bells when struck together. Wish you had seen
them. If you are in eugene, drop by for a listen.
Cheers, Hank
www.murrow.biz/hank
Des & Jan Howard on sat 1 apr 06
Craig
Please don't apologise for posts on glazes & glaze musings.
While I can enjoy the conversations from the other tables,
your type of servings are why I come to this restaurant.
Des
Craig Martell wrote:
> Hi again:
>
> I've been curious about the other blue celadons that are more blue than
> green but are still greener than the sky blue celadons that you can make
> with high potassium glazes. So, I've done some tests. I know, "Get a
> life!"
>
> That's about it. There's a lot more to this but I don't want to hog all
> the Clayart space. Pictures at eleven!
--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
http://www.luepottery.hwy.com.au
Craig Martell on sun 2 apr 06
At 01:00 PM 3/31/2006 -0800, you wrote:
>Wish you had seen them. If you are in eugene, drop by for a listen.
Hello Hank:
Sorry I missed the Stannard pots at the Clayart room. I think I missed a
lot of stuff at NCECA but one can't do it all. Hopefully I'll bump into
you somewhere and you'll have some of these pieces handy.
regards, Craig
Hank Murrow on mon 3 apr 06
On Apr 2, 2006, at 9:38 AM, Craig Martell wrote:
> At 01:00 PM 3/31/2006 -0800, you wrote:
>> Wish you had seen them. If you are in eugene, drop by for a listen.
>
> Hello Hank:
>
> Sorry I missed the Stannard pots at the Clayart room. I think I
> missed a
> lot of stuff at NCECA but one can't do it all. Hopefully I'll bump
> into
> you somewhere and you'll have some of these pieces handy.
Anytime you are in Eugene, Craig. Drop an email if you are headed my
way. And that goes for any Clayart subscriber who has Eugene on their
itinerary. David's pots are as deep as anything i have seen in a
Museum, and deserve to be seen, held, and heard.
Cheers, Hank
www.murrow.biz/hank
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