Baum on sun 2 feb 03
Greetings to the list!
I'm just learning to find my way around a unity formula (I have to
remember to trail a string behind me, so I don't get lost), and ran into
a puzzle with a glaze I'm developing. I checked the archives, and
didn't see any similar questions - I apologize if this has been covered
before.
This is a ^6 Iron Red glaze, modified from a test glaze described in
"Out of the Earth, Into the Fire". I have the expansion, color and
texture where I want them (a consistent, variegated satin-matte red with
good fit on the clays that I use). But. The glaze as it sits is not
stable - it reacts to vinegar after only 8 hours.
The batch recipe and flux unity (from Insight 5) are:
EB0009: ^6 Mg0 Matte - Iron Red
Gerstley Borate 35.00
TALC 15.00
FLINT 27.00
EPK KAOLIN 5.00
CORNWALL STONE 18.00
Add - IRON OXID 15.00
========
115.00
CaO 0.46*
MgO 0.43*
K2O 0.03*
Na2O 0.09*
Al2O3 0.14
B2O3 0.34
SiO2 2.47
Fe2O3 0.25
Here's my question: How much can I increase silica and alumina, and
still keep the character of the glaze? I love the look and feel of the
magnesia matte surface, but I want to be able to use this glaze on
surfaces that *may* come into contact with food, and I'd like for it to
be stable over time regardless.
Any help from the glaze gurus is much appreciated!
Earl Baum
On a delightful, clear Saturday Morning in Atlanta
Chris Schafale on sun 2 feb 03
Hi Earl,
I tested a bunch of iron reds when I was about at the same level of
understanding the unity formula that you are now. What I learned
is that, if you raise the alumina and silica to be within "limits", you
lose the red and just get brown. Your glaze looks like the classic
iron red formula. Adding alumina and/or silica will probably just
make s__t brown.
If you want a challenge, this sounds like the perfect application for
Ian Currie's grid method, where alumina and silica are varied
systematically across a set of 35 glazes. See Ian's website at
http://ian.currie.to and you can find some examples of what the
tiles look like on my site:
http://www.lightonecandle.com/currie.html
Good luck, and good learning. Let us know if you do the
experiment!
Chris
> Greetings to the list!
>
> I'm just learning to find my way around a unity formula (I have to
> remember to trail a string behind me, so I don't get lost), and ran into
> a puzzle with a glaze I'm developing. I checked the archives, and
> didn't see any similar questions - I apologize if this has been covered
> before.
>
> This is a ^6 Iron Red glaze, modified from a test glaze described in
> "Out of the Earth, Into the Fire". I have the expansion, color and
> texture where I want them (a consistent, variegated satin-matte red with
> good fit on the clays that I use). But. The glaze as it sits is not
> stable - it reacts to vinegar after only 8 hours.
>
> The batch recipe and flux unity (from Insight 5) are:
>
> EB0009: ^6 Mg0 Matte - Iron Red
> Gerstley Borate 35.00
> TALC 15.00
> FLINT 27.00
> EPK KAOLIN 5.00
> CORNWALL STONE 18.00
> Add - IRON OXID 15.00
> ========
> 115.00
>
> CaO 0.46*
> MgO 0.43*
> K2O 0.03*
> Na2O 0.09*
> Al2O3 0.14
> B2O3 0.34
> SiO2 2.47
> Fe2O3 0.25
>
> Here's my question: How much can I increase silica and alumina, and
> still keep the character of the glaze? I love the look and feel of the
> magnesia matte surface, but I want to be able to use this glaze on
> surfaces that *may* come into contact with food, and I'd like for it to
> be stable over time regardless.
>
> Any help from the glaze gurus is much appreciated!
>
> Earl Baum
> On a delightful, clear Saturday Morning in Atlanta
>
> ______________________________________________________________________________
> 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@pclink.com.
>
Light One Candle Pottery
Fuquay-Varina, North Carolina, USA
(south of Raleigh)
candle@intrex.net
http://www.lightonecandle.com
Mert & Holly Kilpatrick on sun 2 feb 03
Earl,
I am sure others more knowledgeable than I will answer. But one thing you
really might want to consider before doing a lot more work and getting too
fond of a glaze with that much Gerstley Borate, is that GB is no longer
being mined, the bags that are out there are all that is left, unless there
is some development I haven't heard about (if so, someone, please tell us!)
So if you are going to modify it anyway, you might want to consider one of
the substitute sources of boron such as a frit like 3134 or 3124, or
Gillespie Borate, or Laguna Borate or Boraq.
Holly
East Bangor, PA
----- Original Message -----
From: "Baum"
To:
Sent: Sunday, February 02, 2003 12:01 PM
Subject: ^6 Iron Red Question
> Greetings to the list!
>
> I'm just learning to find my way around a unity formula (I have to
> remember to trail a string behind me, so I don't get lost), and ran into
> a puzzle with a glaze I'm developing. I checked the archives, and
> didn't see any similar questions - I apologize if this has been covered
> before.
>
> This is a ^6 Iron Red glaze, modified from a test glaze described in
> "Out of the Earth, Into the Fire". I have the expansion, color and
> texture where I want them (a consistent, variegated satin-matte red with
> good fit on the clays that I use). But. The glaze as it sits is not
> stable - it reacts to vinegar after only 8 hours.
>
> The batch recipe and flux unity (from Insight 5) are:
>
> EB0009: ^6 Mg0 Matte - Iron Red
> Gerstley Borate 35.00
> TALC 15.00
> FLINT 27.00
> EPK KAOLIN 5.00
> CORNWALL STONE 18.00
> Add - IRON OXID 15.00
> ========
> 115.00
>
> CaO 0.46*
> MgO 0.43*
> K2O 0.03*
> Na2O 0.09*
> Al2O3 0.14
> B2O3 0.34
> SiO2 2.47
> Fe2O3 0.25
>
> Here's my question: How much can I increase silica and alumina, and
> still keep the character of the glaze? I love the look and feel of the
> magnesia matte surface, but I want to be able to use this glaze on
> surfaces that *may* come into contact with food, and I'd like for it to
> be stable over time regardless.
>
> Any help from the glaze gurus is much appreciated!
>
> Earl Baum
> On a delightful, clear Saturday Morning in Atlanta
>
>
____________________________________________________________________________
__
> 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@pclink.com.
Paul Lewing on sun 2 feb 03
Earl, I did a lot of tests of oxidation iron reds a few years ago, maybe 300
or so. The one you have here is pretty typical. If you compare it to a set
of limit formulas, you'll see it's way low in alumina. I found that if the
SiO2:Al2O3 ratio dropped below about 15:1 the glaze was no longer red. I
think Chris is right- you should try one of those grid tiles like Ian Currie
does on this glaze.
Personally, I consider a stable, dependable, bright iron red glaze,
especially a glossy one, at cone 5 or 6 in oxidation to be the Holy Grail of
glaze making. Let me know if you get it and I'll come and kiss your feet.
Paul Lewing, Seattle
Baum on sun 2 feb 03
Thanks to all for the responses!
You've given me some ideas, and some great suggestions. I'll follow up,
and pass on my results. These are the sorts of things that got me into
ceramics in the first place - it's always a challenge...
eb
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Paul Lewing
Sent: Sunday, February 02, 2003 7:17 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: ^6 Iron Red Question
Earl, I did a lot of tests of oxidation iron reds a few years ago, maybe
300 or so. The one you have here is pretty typical. If you compare it
to a set of limit formulas, you'll see it's way low in alumina. I found
that if the SiO2:Al2O3 ratio dropped below about 15:1 the glaze was no
longer red. I think Chris is right- you should try one of those grid
tiles like Ian Currie does on this glaze. Personally, I consider a
stable, dependable, bright iron red glaze, especially a glossy one, at
cone 5 or 6 in oxidation to be the Holy Grail of glaze making. Let me
know if you get it and I'll come and kiss your feet. Paul Lewing,
Seattle
________________________________________________________________________
______
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@pclink.com.
Craig Martell on sun 2 feb 03
Hello Earl:
You've way too much Boron in this glaze. I would suggest that you decrease
the boron and add some soda feldspar. The alumina is too low so you could
bring up the % of kaolin but after you add the feldspar because that will
contribute some alumina to the glaze. Your silica/alumina ratio is too hi
because the alumina content of the glaze is low. When you look at the
silica-boron/alumina ratio, it's even higher. Boron is a glass former as
well as a flux but it produces glass of a lesser quality than glass from
silica.
Just a few suggestions. Good luck, Craig Martell Hopewell, Oregon
David Hewitt on mon 3 feb 03
As others have said, this glaze is low in Alumina and high in Borax. The
general problem of Gerstley Borate being variable if available at all is
another problem.
I would start again. May I suggest that you look at Mike Bailey's book,
'Glazes Cone6', which has a chapter on Orange Red Iron Glazes.
ISBN 0-8122-1782-9, University of Pennsylvania Press.
David
In message , Baum writes
>Greetings to the list!
>
>I'm just learning to find my way around a unity formula (I have to
>remember to trail a string behind me, so I don't get lost), and ran into
>a puzzle with a glaze I'm developing. I checked the archives, and
>didn't see any similar questions - I apologize if this has been covered
>before.
>
>This is a ^6 Iron Red glaze, modified from a test glaze described in
>"Out of the Earth, Into the Fire". I have the expansion, color and
>texture where I want them (a consistent, variegated satin-matte red with
>good fit on the clays that I use). But. The glaze as it sits is not
>stable - it reacts to vinegar after only 8 hours.
>
>The batch recipe and flux unity (from Insight 5) are:
>
>EB0009: ^6 Mg0 Matte - Iron Red
> Gerstley Borate 35.00
> TALC 15.00
> FLINT 27.00
> EPK KAOLIN 5.00
> CORNWALL STONE 18.00
> Add - IRON OXID 15.00
> ========
> 115.00
>
> CaO 0.46*
> MgO 0.43*
> K2O 0.03*
> Na2O 0.09*
> Al2O3 0.14
> B2O3 0.34
> SiO2 2.47
> Fe2O3 0.25
>
>Here's my question: How much can I increase silica and alumina, and
>still keep the character of the glaze? I love the look and feel of the
>magnesia matte surface, but I want to be able to use this glaze on
>surfaces that *may* come into contact with food, and I'd like for it to
>be stable over time regardless.
>
>Any help from the glaze gurus is much appreciated!
>
>Earl Baum
>On a delightful, clear Saturday Morning in Atlanta
--
David Hewitt
David Hewitt Pottery
7 Fairfield Road, Caerleon, Newport,
South Wales, NP18 3DQ.
Tel:- +44 (0) 1633 420647
Fax:- +44 (0) 870 1617274
Web:- http://www.dhpot.demon.co.uk
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