Dick & Gwen Schenz on sun 26 jul 98
Greetings from a lurker:
I have a teacher that gave me the following recipe for a glossy blue glaze
she has for cone 10 reduction firing. She told me that if I try to use
it in a cone 5 oxy firing, that it would be rather matte and not flow. She
was right! The suggestion was made to increase the amount of flux? After
checking in a catalog, I find that Whiting is used as a flux.
Do any of you have a suggestion as to how much it should be increased? or
aven if I am correct in identifying the correct component to increase?
Thanks for any help you may have.
___________________________
Blatant Blue Cone 10
Custer 27
Ball Clay 20
Whiting 19
Silica 32
Cobalt Carbonate 2
______________________________
Richard Schenz
rschenz@primenet.com
PS Some time ago, one of the clayarters posted a little ditty in their
signature concerning the "Golden Years". I wish I had saved it. If anyone
has it,
please send it to me, or post it.
Paul Lewing on mon 27 jul 98
Richard,
I think I'm really the perfect person to answer your questions about
Blatant Blue. That started out life as a celadon shop glaze at
Pottery Northwest here in Seattle. I was the one who tried replacing
the iron with cobalt and named it Blatant Blue. I've been handing it
out as one of the recipes on my sheet of C10 glazes that I give out at
workshops for a good 20 years. Who did you get it from? And where did
they get it?
Now to answer your question. You can't add enough whiting to this
glaze to take it down to cone 5. Whiting is not a powerful enough
flux at cone 5. I've tried to by dumping in flux, and I've tried to
adjust it with glaze software. Cone 10 and cone 5 are just too far
apart to do this without the addition of some more powerful flux or
the addition of quite a bit of boron. And of course, then you've
changed the glaze.
But you're in luck here. This is an easy look to duplicate. Find a
cone 5 clear you like that fits your clay body and add the same amount
of cobalt to it. Chances are it will be pretty similar. Avoid base
glazes with zinc or barium in them, as this will give you a slightly
different shade of blue. Stick to ones with lots of potassium,
sodium, and calcium, and don't put any opacifier in it.
Coincidentally, a longtime customer just returned a piece from about
15 years ago with glue problems (don't ask) the same day I unloaded a
firing that had quite a bit of my cone 5 version of this color, and
they were very similar.
Happy Testing,
Paul Lewing, Seattle
Autumn Downey on mon 27 jul 98
Original recipe
>___________________________
>Blatant Blue Cone 10
>
>Custer 27
>Ball Clay 20
>Whiting 19
>Silica 32
>Cobalt Carbonate 2
>______________________________
>
>Richard Schenz
As an exercise, I thought I'd try to adjust your recipe to melt at a lower
temperature. More than anything it needs the alumina and silica to be
reduced, but that's quite hard to figure out without a program to crunch the
numbers. This recipe might still be a little on the non-melting side. Am
sure you will get lots of responses from much more experienced glaze people
so I will be watching for those too.
Autumn
Blatant Blue (Cone 6) (maybe)
====
Custer.............. 36.00
Ball Clay........... 9.00
Silica.............. 8.00
VOLCANIC ASH........ 30.00
Cobalt Carbonate.... 2.00
========
102.00
CoO 0.06
CaO 0.77*
MgO 0.02*
K2O 0.07*
Na2O 0.14*
TiO2 0.01
Al2O3 0.35
SiO2 3.35
Fe2O3 0.01
Cost/kg 3.55
Si:Al 9.45
SiB:Al 9.45
Expan 7.32
downeya@internorth.com
Yellowknife, NWT, Canada
Edouard Bastarache on mon 27 jul 98
Hello Automn,
there is another way to lower the temperature of your glaze "Blatant blue`:
substitute for Custer spar by Nepheline/syenite and add 10% gerstley
borate.
If it is not enough add more Gerstley borate by 2% increments.
Later,
Edouard Bastarache
edouardb@sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/~edouardb/
----------
> De : Autumn Downey
> A : CLAYART@LSV.UKY.EDU
> Objet : Re: How to adjust a Cone 10 glaze to Cone 5
> Date : 27 juillet, 1998 13:00
>
> Original recipe
>
> >___________________________
> >Blatant Blue Cone 10
> >
> >Custer 27
> >Ball Clay 20
> >Whiting 19
> >Silica 32
> >Cobalt Carbonate 2
> >______________________________
> >
> >Richard Schenz
>
> As an exercise, I thought I'd try to adjust your recipe to melt at a
lower
> temperature. More than anything it needs the alumina and silica to be
> reduced, but that's quite hard to figure out without a program to crunch
the
> numbers. This recipe might still be a little on the non-melting side.
Am
> sure you will get lots of responses from much more experienced glaze
people
> so I will be watching for those too.
>
> Autumn
>
>
> Blatant Blue (Cone 6) (maybe)
> ====
> Custer.............. 36.00
> Ball Clay........... 9.00
> Silica.............. 8.00
> VOLCANIC ASH........ 30.00
> Cobalt Carbonate.... 2.00
> ========
> 102.00
>
> CoO 0.06
> CaO 0.77*
> MgO 0.02*
> K2O 0.07*
> Na2O 0.14*
> TiO2 0.01
> Al2O3 0.35
> SiO2 3.35
> Fe2O3 0.01
>
> Cost/kg 3.55
> Si:Al 9.45
> SiB:Al 9.45
> Expan 7.32
> downeya@internorth.com
> Yellowknife, NWT, Canada
hal mc whinnie on mon 27 jul 98
if you substitute neph syn for whatever feldspar is in the glaze you will
reduce the cone level by at least 2 and maybe 3 cones especiaaly if you
add some borax
On Sun, 26 Jul 1998 20:05:57 -0700 Dick & Gwen Schenz
writes:
>Greetings from a lurker:
>
>I have a teacher that gave me the following recipe for a glossy blue
>glaze
>she has for cone 10 reduction firing. She told me that if I try to
>use
>it in a cone 5 oxy firing, that it would be rather matte and not flow.
>She
>was right! The suggestion was made to increase the amount of flux?
>After
>checking in a catalog, I find that Whiting is used as a flux.
>
>Do any of you have a suggestion as to how much it should be increased?
>or
>aven if I am correct in identifying the correct component to increase?
>
>Thanks for any help you may have.
>___________________________
>Blatant Blue Cone 10
>
>Custer 27
>Ball Clay 20
>Whiting 19
>Silica 32
>Cobalt Carbonate 2
>______________________________
>
>Richard Schenz
>rschenz@primenet.com
>
>PS Some time ago, one of the clayarters posted a little ditty in their
> signature concerning the "Golden Years". I wish I had saved it. If
>anyone
>has it,
> please send it to me, or post it.
>
_____________________________________________________________________
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John Post on tue 28 jul 98
Here's my shot at making this cone 10 glaze a cone 6. I've used all of the
same raw materials and have just lowered the alumina and silica into the
cone 6 range. The small amount of dolomite helps keep the MgO in the flux
column the same for both glazes.
I bet it could be left out of the glaze without creating any noticeable
difference.
If you try it, let us know how it works out for you.
+++++++++++++++++++++++++++++++
+++ Blatant Blue Cone 6 +++
+++++++++++++++++++++++++++++++
Date: 07/28/98
Custer feldspar 141.46 35.4%
Kentucky OM #4 39.96 10 % Hazard!
Dolomite 1.2 0.3%
Whiting 92.31 23.1%
Flint 125.07 31.3% Hazard!
-------- ------
400 100 %
Cobalt carbonate 8.0 2 % Hazard!
===========================
Chemical Analysis
===========================
Na2O 0.06 Al2O3 0.28 SiO2 3.29
K2O 0.12 TiO2 0.01
MgO 0.01 Fe2O3 0.00
CaO 0.75
CoO 0.05
Alumina:Silica ratio is 1.00 : 11.65
Neutral:Acid ratio is 1.00 : 11.68
Alkali:Neutral:Acid ratio is 1.00 : 0.28 : 3.29
Expansion coefficient: 72.7 x 10e-7 per degree C
+++++++++++++++++++++++++++++++++++++++++
+++ Blatant Blue Cone 10 original +++
+++++++++++++++++++++++++++++++++++++++++
Date: 07/28/98
Custer feldspar 108 27 %
Kentucky OM #4 80 20 % Hazard!
Whiting 76 19 %
Flint 128 32 % Hazard!
Cobalt carbonate 8 2 % Hazard!
-------- ------
400 100 %
Cobalt carbonate 8 2 % Hazard!
===========================
Chemical Analysis
===========================
Na2O 0.05 Al2O3 0.37 SiO2 3.77
K2O 0.11 TiO2 0.02
MgO 0.01 Fe2O3 0.00
CaO 0.70
CoO 0.12
Alumina:Silica ratio is 1.00 : 10.13
Neutral:Acid ratio is 1.00 : 10.18
Alkali:Neutral:Acid ratio is 1.00 : 0.37 : 3.80
Expansion coefficient: 68.6 x 10e-7 per degree C
John Post
potter@c3net.net
Sterling Heights, MI USA
Bob Wicks on wed 29 jul 98
----------------------------Original message----------------------------
Richard:
You might try this. According to the Holscher Watts chart on maturation
points of molecular formulas all you have to do is to unify the formula. Then
note that for each .3 mole of silica added will increase the temp one cone and
the reverse is also true. Example is change from ^10 to ^ 5 (5 cones X .3)
means a decrease of .15 moles of silica on the unity formula. I might also
add if you do this it may change other characteristics of the glaze.
Bob
Paul Lewing on thu 30 jul 98
Bob Wicks wrote:
>
> ----------------------------Original message----------------------------
> Richard:
>
> You might try this. According to the Holscher Watts chart on maturation point
Bob
Bob,
This will have even more of an effect on the glaze if you do this math
right and take out 1.5 moles of silica. Gotcha! Seriously, I have
tried to take a lot of my old cone 10 glazes down to cone 5 this way,
and there just isn't enough silica or alumina in this formula to take
it down 5 cones. You have to also add more of a more powerful flux,
or some boron. Very few cone 10 recipes can be adjusted that far just
by doing what Watts suggests, and they certainly won't have the same
surface characteristics.
Paul Lewing, Seattle
Edouard Bastarache on fri 31 jul 98
Hello all,
Harold WcWhinnie in summer 1982 in Ceramics Monthly wrote, speaking of a
glaze named
Dennis Carib Blue Glaze(Cone 10,reduction):"By replacing Custer feldspar
with nepheline syenite
the glaze will mature at Cone 8,with that substitution and an addition of
10% Gerstley borate, the firing
temperature will be lowerred to Cone 6".
I have used this trick as a starting point many times to lower the firing
temp. of Cone 10 glazes to
cone 6; and even to Cone 4 by adding more boron bearing materials like frit
3134.
At Cone 4 i added Gerstley borate and frit 3134 and divided the amount by
2.
Later all,
Edouard Bastarache
edouardb@sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/~edouardb/
----------
> De : Paul Lewing
> A : CLAYART@LSV.UKY.EDU
> Objet : Re: How to adjust a Cone 10 glaze to Cone 5
> Date : 30 juillet, 1998 08:58
>
> ----------------------------Original message----------------------------
> Bob Wicks wrote:
> >
> > ----------------------------Original
message----------------------------
> > Richard:
> >
> > You might try this. According to the Holscher Watts chart on
maturation point
> Bob
>
> Bob,
> This will have even more of an effect on the glaze if you do this math
> right and take out 1.5 moles of silica. Gotcha! Seriously, I have
> tried to take a lot of my old cone 10 glazes down to cone 5 this way,
> and there just isn't enough silica or alumina in this formula to take
> it down 5 cones. You have to also add more of a more powerful flux,
> or some boron. Very few cone 10 recipes can be adjusted that far just
> by doing what Watts suggests, and they certainly won't have the same
> surface characteristics.
>
> Paul Lewing, Seattle
Edouard Bastarache on sat 1 aug 98
Hello all,
please read my yesterday message in which a correction to this one was
sent to
all.
By dividing by 2 i meant "in order to have equal amounts of boron bearing
materials" ;not to reduce the total amount of boron bearing materials by
50%.
Later,
Edouard Bastarache
edouardb@sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/~edouardb/
----------
> De : Edouard Bastarache
> A : CLAYART@LSV.UKY.EDU
> Objet : Re: How to adjust a Cone 10 glaze to Cone 5
> Date : 31 juillet, 1998 16:05
>
> ----------------------------Original message----------------------------
> Hello all,
>
> Harold WcWhinnie in summer 1982 in Ceramics Monthly wrote, speaking of a
> glaze named
> Dennis Carib Blue Glaze(Cone 10,reduction):"By replacing Custer feldspar
> with nepheline syenite
> the glaze will mature at Cone 8,with that substitution and an addition of
> 10% Gerstley borate, the firing
> temperature will be lowerred to Cone 6".
> I have used this trick as a starting point many times to lower the firing
> temp. of Cone 10 glazes to
> cone 6; and even to Cone 4 by adding more boron bearing materials like
frit
> 3134.
> At Cone 4 i added Gerstley borate and frit 3134 and divided the amount
by
> 2.
>
> Later all,
>
> Edouard Bastarache
> edouardb@sorel-tracy.qc.ca
> http://www.sorel-tracy.qc.ca/~edouardb/
>
> ----------
> > De : Paul Lewing
> > A : CLAYART@LSV.UKY.EDU
> > Objet : Re: How to adjust a Cone 10 glaze to Cone 5
> > Date : 30 juillet, 1998 08:58
> >
> > ----------------------------Original
message----------------------------
> > Bob Wicks wrote:
> > >
> > > ----------------------------Original
> message----------------------------
> > > Richard:
> > >
> > > You might try this. According to the Holscher Watts chart on
> maturation point
> > Bob
> >
> > Bob,
> > This will have even more of an effect on the glaze if you do this math
> > right and take out 1.5 moles of silica. Gotcha! Seriously, I have
> > tried to take a lot of my old cone 10 glazes down to cone 5 this way,
> > and there just isn't enough silica or alumina in this formula to take
> > it down 5 cones. You have to also add more of a more powerful flux,
> > or some boron. Very few cone 10 recipes can be adjusted that far just
> > by doing what Watts suggests, and they certainly won't have the same
> > surface characteristics.
> >
> > Paul Lewing, Seattle
hal mc whinnie on sat 1 aug 98
i am glad someone found this article an idea usefull, the system of
simple substitutiosn of feldspars is most usefull all one needs to do is
to consult a list of the feldspars and look at the chemical signs for the
number of molcules of silica present in relation to the molecules of the
feldspar.
On Fri, 31 Jul 1998 16:05:26 EDT Edouard Bastarache
writes:
>----------------------------Original
>message----------------------------
>Hello all,
>
>Harold WcWhinnie in summer 1982 in Ceramics Monthly wrote, speaking of
>a
>glaze named
>Dennis Carib Blue Glaze(Cone 10,reduction):"By replacing Custer
>feldspar
>with nepheline syenite
>the glaze will mature at Cone 8,with that substitution and an addition
>of
>10% Gerstley borate, the firing
>temperature will be lowerred to Cone 6".
>I have used this trick as a starting point many times to lower the
>firing
>temp. of Cone 10 glazes to
>cone 6; and even to Cone 4 by adding more boron bearing materials like
>frit
>3134.
>At Cone 4 i added Gerstley borate and frit 3134 and divided the
>amount by
>2.
>
>Later all,
>
>Edouard Bastarache
>edouardb@sorel-tracy.qc.ca
>http://www.sorel-tracy.qc.ca/~edouardb/
>
>----------
>> De : Paul Lewing
>> A : CLAYART@LSV.UKY.EDU
>> Objet : Re: How to adjust a Cone 10 glaze to Cone 5
>> Date : 30 juillet, 1998 08:58
>>
>> ----------------------------Original
>message----------------------------
>> Bob Wicks wrote:
>> >
>> > ----------------------------Original
>message----------------------------
>> > Richard:
>> >
>> > You might try this. According to the Holscher Watts chart on
>maturation point
>> Bob
>>
>> Bob,
>> This will have even more of an effect on the glaze if you do this
>math
>> right and take out 1.5 moles of silica. Gotcha! Seriously, I have
>> tried to take a lot of my old cone 10 glazes down to cone 5 this
>way,
>> and there just isn't enough silica or alumina in this formula to
>take
>> it down 5 cones. You have to also add more of a more powerful flux,
>> or some boron. Very few cone 10 recipes can be adjusted that far
>just
>> by doing what Watts suggests, and they certainly won't have the same
>> surface characteristics.
>>
>> Paul Lewing, Seattle
>
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Bob Wicks on sun 2 aug 98
Paul:
I goofed. Yes, my math was a bit off. I was trying to answer the main part
of the question and should have checked more careful just where the decimal
point was to go. Even my answer is not too good, because when you lower the
point of vitrification by 5 cones, changing your formula by just lowering the
melt point by .3 moles per cone does not leave enough silica to really form a
good glass. There were some other responses that had some merit and the one
that interested me was the suggestion of using Calcium Gerstly Borate. I
think you may find the answer here. Even the Holscher Watts Chart has some
short comings. Rather its more on how we make the application of it.
Good to hear from you.
Bob
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