carolholmeskerr@rogers.com on fri 18 mar 11
A colleague at our co-op studio bought this bowl several years ago from a
potter in Quebec who developed this glaze with another potter and swore
themselves to secrecy as to the recipe. The potter who made this bowl is
deceased so there is no way of finding out the recipe. This crackle glaz=
=3D
e
is not raku. It looks like it is on cone 6 stoneware clay but it could b=
=3D
e
fired to a higher temp. Whatever the temp the clay seems to be vitrified.=
=3D
=3D0D
=3D0D
We would like to make a glaze like this for the studio. Does anyone have=
=3D
a
recipe for a crackle glaze like this that is fired to cone 6 in oxidation=
=3D
?=3D20
Is this even possible? If so how did they get that black and white crack=
=3D
le
definition?=3D0D
=3D0D
Thanks for any light you can shed on this.=3D0D
=3D0D
Carol - Ottawa - www.gladstoneclayworks.com=3D0D
=3D0D
=3DEF=3DBB=3DBF =3DEF=3DBB=3DBF =3D0D
=3D20
paul gerhold on sun 20 mar 11
Carol,
This is a project that can consume infinite amounts of time since the
crackles are a result of shrinkage difference between clay and glaze. Even
if you had the glaze you would probably need to do a lot of experimenting o=
=3D
n
the clay.
You can find potters who are currently doing similar pieces and if they are
really kind maybe they will share. If you can get the big crackles there
are lots of ways to color..Tea, india ink, contrasting lower fired glaze
etc.
Paul
On Fri, Mar 18, 2011 at 9:56 PM, carolholmeskerr@rogers.com <
carolholmeskerr@rogers.com> wrote:
> A colleague at our co-op studio bought this bowl several years ago from a
> potter in Quebec who developed this glaze with another potter and swore
> themselves to secrecy as to the recipe. The potter who made this bowl is
> deceased so there is no way of finding out the recipe. This crackle glaz=
=3D
e
> is not raku. It looks like it is on cone 6 stoneware clay but it could b=
=3D
e
> fired to a higher temp. Whatever the temp the clay seems to be vitrified.
>
> We would like to make a glaze like this for the studio. Does anyone have=
=3D
a
> recipe for a crackle glaze like this that is fired to cone 6 in oxidation=
=3D
?
> Is this even possible? If so how did they get that black and white crack=
=3D
le
> definition?
>
> Thanks for any light you can shed on this.
>
> Carol - Ottawa - www.gladstoneclayworks.com
>
> =3DEF=3DBB=3DBF =3DEF=3DBB=3DBF
>
>
MJ on sun 20 mar 11
Hi Carol - I don't have a recipe but I hear that Georgies makes a few
crackle glazes for cone 6. If you are interested in buying commercial
glazes, this might be an option - especially if you only need/want a small
amount. Just google Georgies crackle glazes to get info.
Cheers, MJ
ivor and olive lewis on mon 21 mar 11
Dear Carol
Perhaps this is one of those problems that is more easily solved by tapping
into the facility of a glaze calculation program.
I would solve it this way. Select a glaze whose recipe is known that sits
well on one of the standard clays in your studio.
Use information from standard text books (Rhodes, Hamer, Cooper and Royle,
Frazer ) and select one of the ingredients which is known to alleviate the
defect of Crazing. Reduce this by arbitrary amounts as though you were doin=
g
a line blend and recalculate the new glaze recipes. Then prepare samples an=
d
test them.
Regards,
Ivor Lewis,
REDHILL,
South Australia
Lili Krakowski on mon 21 mar 11
I never read Racine, but know this quote. Berenice is separated from the
man she loves, but who does not love her...And at some [tragic] point she
cries (poignantly no doubt, and, of course, in French) "These days too long
for me, will seem too short for him!" Dreadful for one, great for the
other...
So. A crackle glaze is one that crazes. And crazing is considered a bad
defect. Generally a crackle glaze--and I know little about them and have
never worked with one--have large mesh crazes, not small ones. Hobart
Cowles claimed that large mesh crazes are small mesh crazes on the way to b=
e
ok...in other words, from the crazing point of view, small crazes are
"worse" than big ones.
So what I would do first is to take a glaze that crazes badly--lots of fine
mesh stuff--and add alumina to it a little bit at a time, as though trying
to cure the craze. If all goes well--and it may--you soon will have a
glaze that has just the right "mesh" crackle.
Then you can stain the crackles as you wish. I have heard--again I know
nothing really about these glazes--that one can wash a dark glaze into the
crackles, wipe off all excess, and refire. No idea if that works. Or, as
said by someone else, rub India ink into the cracks, or strong black tea.
The Potter's Book of Glaze Recipes by Emmanuel Cooper lists this as a clear
crackle glaze cone 5, and up to 8.
Cornish Stone 80
whiting 16
bentonite 4
.182 Na2O
.117 K2O
.013 MgO
.688 CaO
.491 Al2O3
3.716 SiO2
.
73.7 Exp
-----------------------------------
Calculations by GlazeMasterT
Watery clear glaze
Soda spar 40
whiting 20
ball clay 8
china clay (kaolin) 5
Flint 27
calculated with the following:
40 Feldspar--Kona F4
20 Whiting
8 Ball Clay--Old Mine #4
5 Kaolin--EPK
27 Flint
.154 Na2O
.073 K2O
.007 MgO
.765 CaO
.401 Al2O3
3.353 SiO2
72.9 Exp
Calculations by GlazeMasterT
You will note these glazes are high in silica and desperately low in
alumina.
Were I doing this I would test these glazes, of course, but otherwise take
any of my glazes and remove alumina.
Lettuce know what happens.
Lili Krakowski
Be of good courage
Edouard Bastarache on mon 21 mar 11
YAY Lilli
"I never read Racine, but know this quote. Berenice is separated from t=
=3D
he
man she loves, but who does not love her...And at some [tragic] point sh=
=3D
e
cries (poignantly no doubt, and, of course, in French) "These days too l=
=3D
ong
for me, will seem too short for him!" Dreadful for one, great for the
other..."
I studied all those guys when I was young : Racine, Corneille, Moli=3DE8re =
=3D
and=3D20
Boileau;.
actually from Ronsard to J.P. Sartre, including
Monseigneur de Bossuet..
Great days!!!
Gis,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.flickr.com/photos/30058682@N00/
http://edouardbastarache.blogspot.com/
http://www.facebook.com/edouard.bastarache
http://blogsalbertbastarache.blogspot.com/
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