Ellie Blair on sun 3 aug 03
I am having a problem with crazing in my crystalline glazes. I use the s=
ame base glaze just different oxides for color. The crazing is the worst=
on glazes containing manganese/black nickel or cobalt carbonate. The po=
ts are all made from the same clay and bisque fired to 08. The treatment=
during firing is the same for all of the glazes so why are some and not =
all crazing?
Thanks
Ellie Blair
blairea53@msn.com
Ababi on sun 3 aug 03
Hello Ellie
The question is why it did not crease before.
I have two claybodies that are fitting to the glazes (or the other way
around).
My recipe when it has 3 nickel 2 titanium and one RIO does not crease.
When you add cobalt manganese and nickel you add flux. You have such a
big amount of flux anyway!
Perhaps you should decrease the frit? Lithium? I can try it with Matrix.
You can send me the recipe in E mail and your beautiful crazed ware in
snail mail.
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910
http://www.matrix2000.co.nz/Matrix%20Demo/Ababi.htm]
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Ellie Blair
Sent: Sunday, August 03, 2003 5:36 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Glaze problem for the gurus
I am having a problem with crazing in my crystalline glazes. I use the
same base glaze just different oxides for color. The crazing is the
worst on glazes containing manganese/black nickel or cobalt carbonate.
The pots are all made from the same clay and bisque fired to 08. The
treatment during firing is the same for all of the glazes so why are
some and not all crazing?
Thanks
Ellie Blair
blairea53@msn.com
________________________________________________________________________
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Ron Roy on wed 6 aug 03
All the oxides we use have different rates of expansion and contraction -
but unless you are using significant amounts I would not expect them to
cause crazing.
I am looking at the list of oxides and their relative expansion rates in
the back of the Hamer book - page 379 in the 4th edition - and I see no
correlation with your results.
I suspect this may have to do with the type of crystals and how they affect
the glaze surrounding the crystals.
When crystals from they take silica from the surrounding glaze - silica
starved glazes will be more susceptible to crazing.
If you want to send me your base glaze I may be able to adjust it - or
perhaps you can add some silica to it till it stops crazing.
This is mostly guess work on my part - I have no experience with crystal glazes.
RR
>I am having a problem with crazing in my crystalline glazes. I use the
>same base glaze just different oxides for color. The crazing is the worst
>on glazes containing manganese/black nickel or cobalt carbonate. The pots
>are all made from the same clay and bisque fired to 08. The treatment
>during firing is the same for all of the glazes so why are some and not
>all crazing?
>Thanks
>Ellie Blair
>blairea53@msn.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on wed 6 aug 03
Cobalt and Manganese help melting - Nickel is a refractory.
>When you add cobalt manganese and nickel you add flux.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ababi on wed 6 aug 03
Yes I knew I might be wrong
Sorry
I should check thanks ababi
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Ron Roy
Sent: Wednesday, August 06, 2003 8:57 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Glaze problem for the gurus
Cobalt and Manganese help melting - Nickel is a refractory.
.
Ellie Blair on wed 6 aug 03
Hi Ron,
I realize that when you add cobalt, manganese and nickel you add flux but=
why is the crazing only on the manganese and nickel. Same clay body on =
all. Same firing, different placement in the kiln. I have been playing =
with the amounts of oxides but only seem to be having trouble with the ma=
nganese and nickel and sometimes red iron oxide when used as the only col=
or oxide. I am still stumped.
Ellie Blair
Blair Pottery
Lawrence, Kansas
blairea53@msn.com
----- Original Message -----
From: Ron Roy
Sent: Wednesday, August 06, 2003 2:05 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Glaze problem for the gurus
Cobalt and Manganese help melting - Nickel is a refractory.
>When you add cobalt manganese and nickel you add flux.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
_________________________________________________________________________=
_____
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at melpots@pclin=
k.com.
Ellie Blair on wed 6 aug 03
Hi Ron
Here is my base glaze recipe.
Ferro Frit 3110 54.0
Zinc Oxide 24.6
Flint 14.9
titanium 4.0
epk kaolin .5
Manganese dioxide 4%
Black nickel 1%
also
Base + 4% red iron oxide
These are the two that I have the most crazing on. It is not so severe t=
hat it cracks the glaze all the way through but it is noticeable and I wo=
uld like to correct it. What I have been doing hasn't been working. =20
Thanks
Ellie Blair
blairea53@msn.com
----- Original Message -----
From: Ron Roy
Sent: Wednesday, August 06, 2003 2:05 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Glaze problem for the gurus
All the oxides we use have different rates of expansion and contraction -
but unless you are using significant amounts I would not expect them to
cause crazing.
I am looking at the list of oxides and their relative expansion rates in
the back of the Hamer book - page 379 in the 4th edition - and I see no
correlation with your results.
I suspect this may have to do with the type of crystals and how they affe=
ct
the glaze surrounding the crystals.
When crystals from they take silica from the surrounding glaze - silica
starved glazes will be more susceptible to crazing.
If you want to send me your base glaze I may be able to adjust it - or
perhaps you can add some silica to it till it stops crazing.
This is mostly guess work on my part - I have no experience with crystal =
glazes.
RR
>I am having a problem with crazing in my crystalline glazes. I use the
>same base glaze just different oxides for color. The crazing is the wor=
st
>on glazes containing manganese/black nickel or cobalt carbonate. The po=
ts
>are all made from the same clay and bisque fired to 08. The treatment
>during firing is the same for all of the glazes so why are some and not
>all crazing?
>Thanks
>Ellie Blair
>blairea53@msn.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
_________________________________________________________________________=
_____
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at melpots@pclin=
k.com.
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