Nav44@aol.com on thu 12 aug 99
Do you have a recipe for or know of a commercial ready made oxidation
(electric kiln) celadon glaze for stoneware?
Josh Lynch on fri 13 aug 99
Copper plus iron in a clear base glaze could yeild a good color. Or if
you wish to get more involved, alkaline dominated base glazes yeild
blue-blue green-aqua, and in my experience glazes with larger amounts
of gerstley borate will yeild forest greens. So one could adjust the
amount of boric oxide and alkaline oxides for color response.
--- Nav44@aol.com wrote:
> ----------------------------Original
> message----------------------------
> Do you have a recipe for or know of a commercial
> ready made oxidation
> (electric kiln) celadon glaze for stoneware?
>
_________________________________________________________
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Mike Bailey on fri 13 aug 99
In message , Nav44@aol.com writes
>----------------------------Original message----------------------------
>Do you have a recipe for or know of a commercial ready made oxidation
>(electric kiln) celadon glaze for stoneware?
>
The following is a cone 8 celadon looking glaze. At least that's what we
call it! Its a grey green coloured glaze when fired oxidised.
I haven't found a really good match for a genuine celadon which is a
transparent glaze coloured with black iron oxide (reduced iron) in
solution.
This glaze is opaque (from the tin oxide) and coloured green with
copper.
BP31S Celadon Cone 8.
Potash Feldspar 33
China Clay 15
Talc 21
Whiting 12
Zinc Oxide 3
Quartz 16
+
Copper Oxide 3
Tin Oxide 5
Analysis K2O 0.11
Na2O 0.04
CaO 0.29
MgO 0.39
CuO 0.09
ZnO 0.09
Al2O3 0.26
SiO2 2.27
SnO2 0.08
To get it to work at a lower temperature I'd lower the amount of china
clay in the recipe and possibly also increase the Zinc Oxide.
Good luck,
Mike.
--
Mike Bailey. Bath. U.K.
Janet Kaiser on sat 14 aug 99
-----Original Message-----
>Do you have a recipe for or know of a commercial ready made oxidation
>(electric kiln) celadon glaze for stoneware?
>
The following is a cone 8 celadon looking glaze. At least that's what we
call it! Its a grey green coloured glaze when fired oxidised.
I haven't found a really good match for a genuine celadon which is a
transparent glaze coloured with black iron oxide (reduced iron) in
solution.
This glaze is opaque (from the tin oxide) and coloured green with
copper.
BP31S Celadon Cone 8.
Potash Feldspar 33
China Clay 15
Talc 21
Whiting 12
Zinc Oxide 3
Quartz 16
+
Copper Oxide 3
Tin Oxide 5
Analysis K2O 0.11
Na2O 0.04
CaO 0.29
MgO 0.39
CuO 0.09
ZnO 0.09
Al2O3 0.26
SiO2 2.27
SnO2 0.08
To get it to work at a lower temperature I'd lower the amount of china
clay in the recipe and possibly also increase the Zinc Oxide. Good luck,
Mike Bailey. Bath. U.K.
_________________________________
Now you are talking! So much talk of Shino on this list, I thought good old
Celadon was a thing of the past out in the "real world"...
It has always been my understanding that a true celadon can only be produced
in reduction.... Although Mike has posted the above "look alike" there can
never be a substitute because of the intrinsic qualities of a celadon. Why
this was my immediate reaction, sent me to my celadon notes, which I pass on
here for what it is worth:
Celadon (aka Celedon) is the general name given to a colour range of subtle
green to blue-grey glazes, deriving from iron in reduction. Yueh ware (which
date back to the early Han period in China) were the forebears of the later
Sung celadons. These extremely fine celadons had a quality likened to jade,
both in texture and colour(s). The quality and colour is best on porcelain
or pale bodied stoneware, although it can also produce a rich olive on
darker bodies.
0.5% to 2.0% of ferric iron is added to a transparent glaze, which should be
applied fairly generously to obtain the depth and richness of colour and to
maintain the iron in the ferrous state during cooling i.e. in reduction. A
particular celadon quality of slight opacity is due to minute bubbles in the
glaze.
Cardew suggests a viscous glaze with an RO 0.25-0.45 kNaO and 0.55-0.75 CaO
with very little magnesia. This may eliminate some wood ashes from which the
early celadons are thought to derive. Rhodes suggests adding a little bone
ash to provide opalescence. See Bernhard Leach's "Potter's Book" for a
several recipes which include ochre (up to 9%) as all or part of the iron
content, also black iron instead of ferric.
The celadon I developed was based on the following recipe:
China clay.............. 07.5
Potash feldspar..... 45.0
Whiting................... 17.5
Quartz..................... 27.5
Ferric iron............... 02.5
Sorry, but I no longer have the follow up notes. It was (gas) fired to
1260-80 deg. Celsius. With Celadon being a reduced stoneware glaze, it has a
wider firing range than oxidised glazes, without any of the violent
character changes that can occur with the latter.
After going through these ancient notes of mine, I see nothing to change my
first reaction: Celadon can only be produced in reduction!! It is, after
all, more than just a colour... It is the quality of the glaze akin to jade
which those ancient Chinese prized.
Janet Kaiser
Awaiting the slap on the wrist from all the experts but unrepentant until I
do and admiring tile #418 brought in person by the Brit who had it made for
The Path in Oman (name of native potter unknown).
The Chapel of Art, Criccieth, GB-Wales
Home of The International Potters Path
URL: http://www.the-coa.org.uk
EMAIL: postbox@the-coa.org.uk
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