Helllll@AOL.COM on mon 30 oct 00
Hello...
Awhile back, Craig posted a glaze recipe he had come up with for a blue
celadon ... well, we have mixed it up and been trying it out ... and so far
it is the bluest of all the celadons we have tried... I have fired it twice,
on Laguna's B-Mix... It is very blue almost baby blue... Crazes like crazy,
and has tiny bubbles in it ... if this is used on a nonwhite clay such as
Laguna's Rods Bod it turns butt ugly and kinda milky largely because of the
tiny bubbles turn the glaze opaque ... also, it will settle like cement in
the bucket... Epson Salts seemed to fix that...
Craig Martell's Blue Celadon2 10R
Custer feldspar 62.34
Whiting 11.06
Silica 22.32
Barium Carbonate 4.28
-------
100.00
Black Iron Oxide 1.0
ed on tue 31 oct 00
CRAIG,
DOES YOUR REVISED FORMULA DELIBERATELY OMIT BLACK IRON OXIDE 1.0??
ED
-----Original Message-----
From: Craig Martell
To: CLAYART@LSV.CERAMICS.ORG
Date: Tuesday, October 31, 2000 4:16 PM
Subject: Re: Craig Martell's Blue Celadon2 10R
>Hi to the gents in Oklahelllma:
>
>The crazing may be related to the claybody too. The glaze expansion is not
>real high but it could be a bit lower. The problem with the blue celadons
>is the potash content of the feldspars. Custer and G-200 are both around
>10% so you get a bit of unwanted soda. I use Kingman which has about 12%
>potassium and it's a bit easier to get the formula into the range for good
>blues and good fit. In the glaze that you tried, the calcium is about .2
>moles too low and the potash is at .29 instead of .3 and there's not much I
>can do with a custer recipe to get it closer than that. The other pisser
>is that when you start adding other fluxes of lower expansion to get better
>fit the color goes in the toilet. Blue celadons are pretty much K
>Feldspar-Limestone fluxed glazes.
>
>In regard to the suspension, try adding about 2% macaloid, vee gum cer, or
>hectabrite and if you can ball mill the glaze this will really help. I use
>2% Hectabrite and ball mill the glaze for one hour. This homogenizes the
>grind a bit and disperses the iron. Even after weeks of setting, the glaze
>does not settle to a hard mass and stirs up well and stays suspended. I've
>been finding that ball milled glazes suspend better than most
>others. Another thing about these glazes without clays for suspension is
>ease of very thick application. It's important for a celadon to be applied
>at least medium to thick for good depth and color and these clayless
>versions will do that very well without cracking and crawling.
>
>Try some other white clays and see if you get better fit. Grolleg
>porcelains are the very best for these celadons. You can also apply a
>Grolleg slip to stonewares and other porcelains.
>
>Here is an adjusted version of the glaze. More silica and a bit lower
>expansion.
>
>later, Craig....thanks for the feedback on the glaze
>
> custer feldspar..... 59.37 59.37%
> whiting............. 10.53 10.53%
> barium carbonate.... 4.08 4.08%
> silica.............. 26.02 26.02%
> ========
> 100.00
>
> BaO 0.09* 3.35%
> CaO 0.49* 6.45%
> K2O 0.29* 6.46%
> Na2O 0.13* 1.83%
> Al2O3 0.46 10.91%
> SiO2 5.02 70.93%
> Fe2O3 0.00 0.08%
>
> Cost/kg 0.43
> Si:Al 11.04
> SiB:Al 11.04
> Expan 7.41
>
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Craig Martell on tue 31 oct 00
Hi to the gents in Oklahelllma:
The crazing may be related to the claybody too. The glaze expansion is not
real high but it could be a bit lower. The problem with the blue celadons
is the potash content of the feldspars. Custer and G-200 are both around
10% so you get a bit of unwanted soda. I use Kingman which has about 12%
potassium and it's a bit easier to get the formula into the range for good
blues and good fit. In the glaze that you tried, the calcium is about .2
moles too low and the potash is at .29 instead of .3 and there's not much I
can do with a custer recipe to get it closer than that. The other pisser
is that when you start adding other fluxes of lower expansion to get better
fit the color goes in the toilet. Blue celadons are pretty much K
Feldspar-Limestone fluxed glazes.
In regard to the suspension, try adding about 2% macaloid, vee gum cer, or
hectabrite and if you can ball mill the glaze this will really help. I use
2% Hectabrite and ball mill the glaze for one hour. This homogenizes the
grind a bit and disperses the iron. Even after weeks of setting, the glaze
does not settle to a hard mass and stirs up well and stays suspended. I've
been finding that ball milled glazes suspend better than most
others. Another thing about these glazes without clays for suspension is
ease of very thick application. It's important for a celadon to be applied
at least medium to thick for good depth and color and these clayless
versions will do that very well without cracking and crawling.
Try some other white clays and see if you get better fit. Grolleg
porcelains are the very best for these celadons. You can also apply a
Grolleg slip to stonewares and other porcelains.
Here is an adjusted version of the glaze. More silica and a bit lower
expansion.
later, Craig....thanks for the feedback on the glaze
custer feldspar..... 59.37 59.37%
whiting............. 10.53 10.53%
barium carbonate.... 4.08 4.08%
silica.............. 26.02 26.02%
========
100.00
BaO 0.09* 3.35%
CaO 0.49* 6.45%
K2O 0.29* 6.46%
Na2O 0.13* 1.83%
Al2O3 0.46 10.91%
SiO2 5.02 70.93%
Fe2O3 0.00 0.08%
Cost/kg 0.43
Si:Al 11.04
SiB:Al 11.04
Expan 7.41
Craig Martell on wed 1 nov 00
Ed wanted to know:
>DOES YOUR REVISED FORMULA DELIBERATELY OMIT BLACK IRON OXIDE 1.0??
Rats! I forgot to post the colorant. No, I will always add the iron for
color.
later, Craig Martell in Oregon
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