Linda Knapp on sun 1 jun 03
I am test firing my new kiln as I type and can't wait to try it with
pots in it next. Problem is that I have been formulating and testing
glazes for c10-11 Reduction until now and plan to fire this kiln to c6 ox.
Anyway I want to check my work here:
I have an Oil Spot (From an old CM I believe) which I like in the c10
firing - It is especially nice in oxidation spots in that kiln though
so I want to try it in my electric kiln.
Original recipe:
John's Oil Spot ^10-^11
Dolomite .... 44
Whiting ..... 44
Kona F4 .....573
EPK ......... 97
Silica ......242
Cobalt Carb . 50
Iron Oxide . 80
Looking at it with John H's GlazeMaster Program (Thank you John for a
great piece of software!) and comparing it to Ron and John's ^6 limits
the KNaO is High as is the Alumina and Silica - The KNaO I will ignore
(as it is high for ^10 limits also) and look only at the Alumina and
Silica for now. Looks like I can delete the EPK and lower the Silica to
about 100 and be ok. Does that look resonable to you people? I hope to
fire this week so I thought I would try both the original ^10 glaze
which I have already mixed and a reformulated version.
This is sooooo much fun!
Cheers!
Linda
Tony Hansen on mon 2 jun 03
To melt a cone 10 glaze at cone 6 you are going to need
boron, probably plenty of it (e.g. 0.2 molar). That means
frit, gerstley borate, etc. The other main alternative is
zinc, and it has too many problems.
However your comment about the expansion is very true.
Moving a cone 10 recipe down means increasing flux or
reduce silica and alumina, both increase the thermal
expansion. Boron however reduces melting and holds
down the expansion.
-------8<--------
Linda wrote: < Looks like I can delete the EPK and lower the Silica to
about 100 and be ok. Does that look resonable to you people?>
In trying to change a cone 10 glaze to cone 6 she wants to do the above.
I would not recommend eliminating the EPK. You\'ll be left with no
clay in the glaze, making for a glaze that will have suspension
problems and possibly fit problems. I\'d suggest replacing the F-4
spar with Neph. Sy. as a starting point.
Bill
--------
Tony Hansen, Digitalfire Corp.
Dewitt on mon 2 jun 03
>
>I have an Oil Spot (From an old CM I believe) which I like in the c10
>firing - It is especially nice in oxidation spots in that kiln though
>so I want to try it in my electric kiln.
Take a look at the article by John Britt at=20
http://www.ceramicsmonthly.org/mustreads/oilspot.asp. He says "Oil spots=20
are created by the thermal reduction of iron. At approximately Cone 10=20
(2350=B0F)" . That will make it tough to lower your glaze to ^6. There=
are=20
some ^6 oil spot glaze recipes floating around, but they don't really look=
=20
the same.
deg
Tony Hansen on mon 2 jun 03
Switching a glaze from 10 to 6 requires major
surgery, check this page for more information:
http://digitalfire.ab.ca/cermat/education/101.php
-------8<--------
I am test firing my new kiln as I type and can\'t wait to try it with
pots in it next. Problem is that I have been formulating and testing
glazes for c10-11 Reduction until now and plan to fire this kiln to c6 ox.
--------
Tony Hansen, Digitalfire Corp.
John Hesselberth on mon 2 jun 03
Hi Linda,
Lowering a glaze by 4 cones without changing the aesthetics is a real
challenge. But here are some things I would try. I would keep
silica/alumina ratio constant and lower their totals to within range.
That is probably essentially what you have done in your proposed test.
As a second try I would keep everything else the same (in unity terms)
and add boron--say about 0.2-0.3. That will give you the chance to use
the formula to recipe capability in GlazeMaster--it's lots of fun once
you have worked through it a couple times.
And the third thing I would do is find a good oil spot recipe for cone
6. There is one on my web site that Carol Tripp uses and likes. She
also had it leach tested and it is quite stable. You might try it with
your colorant mix instead of or in addition to Carol's. You can find it
at:
http://www.frogpondpottery.com/glazestability/glaze0025.html
And thanks for your kind comments about the software!
Regards,
John
On Monday, June 2, 2003, at 02:36 AM, Linda Knapp wrote:
> I am test firing my new kiln as I type and can't wait to try it with
> pots in it next. Problem is that I have been formulating and testing
> glazes for c10-11 Reduction until now and plan to fire this kiln to c6
> ox.
>
> Anyway I want to check my work here:
>
> I have an Oil Spot (From an old CM I believe) which I like in the c10
> firing - It is especially nice in oxidation spots in that kiln though
> so I want to try it in my electric kiln.
>
> Original recipe:
> John's Oil Spot ^10-^11
> Dolomite .... 44
> Whiting ..... 44
> Kona F4 .....573
> EPK ......... 97
> Silica ......242
> Cobalt Carb . 50
> Iron Oxide . 80
>
> Looking at it with John H's GlazeMaster Program (Thank you John for a
> great piece of software!) and comparing it to Ron and John's ^6 limits
> the KNaO is High as is the Alumina and Silica - The KNaO I will ignore
> (as it is high for ^10 limits also) and look only at the Alumina and
> Silica for now. Looks like I can delete the EPK and lower the Silica to
> about 100 and be ok. Does that look resonable to you people? I hope to
> fire this week so I thought I would try both the original ^10 glaze
> which I have already mixed and a reformulated version.
>
> This is sooooo much fun!
> Cheers!
> Linda
>
> _______________________________________________________________________
> _______
> 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.
>
johnpost@WIDEOPENWEST.COM on mon 2 jun 03
Hi Linda,
You are right in that the oil spot glaze you are seeking
occurs in oxidation. If you change the alumina and silica
values for this glaze in an attempt to make it fire at cone
6 instead of cone 10, you may lose the oil spots.
Oil spots happen when iron precipitates on the surface of
the fired glaze. I have made some Ian Currie grids to look
for oil spots and I have found them to occur in the glazes
that are high in both alumina and silica. If I was trying
to change this glaze to a cone 6, I would take the fluxes,
dolomite, whiting, Kona F-4 along with the colorants and use
them as the base for a Currie grid. This will allow you to
see how the alumina and silica levels impact the oil spots.
From my experiments with oxidation cone 6-7 oil spots, I
have found that they are outside of the normal limits, being
higher in both alumina and silica.
(Ian Currie has two books out about his grid method)
Cheers,
John Post
>
> I have an Oil Spot (From an old CM I believe) which I like
> in the c10 firing - It is especially nice in oxidation
> spots in that kiln though so I want to try it in my
> electric kiln.
> Original recipe:
> John's Oil Spot ^10-^11
> Dolomite .... 44
> Whiting ..... 44
> Kona F4 .....573
> EPK ......... 97
> Silica ......242
> Cobalt Carb . 50
> Iron Oxide . 80
>
> Looking at it with John H's GlazeMaster Program (Thank you
> John for a great piece of software!) and comparing it to
> Ron and John's ^6 limits the KNaO is High as is the
> Alumina and Silica - The KNaO I will ignore (as it is high
> for ^10 limits also) and look only at the Alumina and
> Silica for now. Looks like I can delete the EPK and lower
> the Silica to about 100 and be ok. Does that look
> resonable to you people? I hope to fire this week so I
> thought I would try both the original ^10 glaze which I
> have already mixed and a reformulated version.
> This is sooooo much fun!
> Cheers!
> Linda
>
Paul Lewing on mon 2 jun 03
on 6/1/03 10:36 PM, Linda Knapp at linda@BOZUK.ORG wrote:
> Problem is that I have been formulating and testing
> glazes for c10-11 Reduction until now and plan to fire this kiln to c6 ox.
> I have an Oil Spot (From an old CM I believe) which I like in the c10
> firing - It is especially nice in oxidation spots in that kiln though
> so I want to try it in my electric kiln.
Hi, Linda. I think you'll find that in order to change a cone 10 glaze to a
cone 6 glaze, you'll have to change it so much that you won't recognize it.
And even though you say it has looked OK in the more oxidized parts of your
gas kiln, usually that's still not the same atmosphere as an electric kiln.
Most people who switch from high-fire reduction to mid-range oxidation don't
realize that the atmosphere switch makes more difference than the
temperature switch.
The problem in lowering the firing temperature that far is that, often, even
if you take out all the available alumina or silica that's not chemically
tied up in one of the other materials, there's still too much to let it melt
at the lower temperature. So you end up switching to other materials with
lower silica or alumina levels, or adding some boron. Before you know it,
it's completely different.
By all means go ahead and make the tests, though. You'll learn a lot, you
might get something different but equally wonderful, and, who knows, it
might even work!
Good luck,
Paul Lewing, Seattle
william schran on mon 2 jun 03
Linda wrote: < Looks like I can delete the EPK and lower the Silica to
about 100 and be ok. Does that look resonable to you people?>
In trying to change a cone 10 glaze to cone 6 she wants to do the above.
I would not recommend eliminating the EPK. You'll be left with no
clay in the glaze, making for a glaze that will have suspension
problems and possibly fit problems. I'd suggest replacing the F-4
spar with Neph. Sy. as a starting point.
Bill
Ron Roy on tue 3 jun 03
A few years ago I might have agreed with this but I think there is another
factor that has been completely overlooked until recently.
Most high fire kilns cool slower than electric kilns and that slower
cooling has a profound effect on glazes.
When trying to duplicate cone 10 glazes at cone 6 it is important to know
how fast (how slow) they cooled in the gas kiln. Trying to duplicate that
cycle is probably crucial to maximize chances of success.
Perhaps I should include an example of why I think this - at the risk of
someone complaining about plugging our book.
When showing test tiles of some of our glazes to experienced potters - John
said they did not believe they were not fired in reduction. I have to admit
- I have seen very few cone 6 glazes that break up so well over raised
decoration and edges. Most cone 6 glazes that act that way are over fluxed
to the point where the glaze is actually moving into the clay looking for
silica to melt. Those types of glazes are not durable because they don't
have enough silica and/or alumina.
Our glazes are balanced, durable glazes with plenty of silica and alumina -
try them with a regular cool down in most electric kilns and they become
quite ordinary - nice enough but not any where as interesting as with a
slower cooling.
So I am now not so sure that it the reduction that makes all the difference
- the iron spotting yes - the particular colours from reduction - yes - but
the formation of crystals from slower cooling - no.
RR
>Most people who switch from high-fire reduction to mid-range oxidation don't
>realize that the atmosphere switch makes more difference than the
>temperature switch.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on tue 3 jun 03
Hi Linda,
I have no experience with oil spot glazes. Keeping that in mind - here is
what I would do.
Replace the F4 spar with Neph Sy and the EPK with a ball clay - you will
have to adjust the alumina till it matches the original level - then adjust
the SiO2 till the ratio is the same as the original - and add 2% bentonite
to counter the deflocculation the Neph Sy will cause. I don't think the
glaze will melt properly at cone 6 with only those additions however.
The next step would be to add frit 3110 1% at a time - adjusting SiO2
levels so the ratio is the same as the original. I say 3110 because it has
not much Al2O3 and not much B2O3 but lots of KNaO - I am unsure if the
boron will help the kind of action needed to get the oil spots.
I would do another series using frit 3134 - it has lots of boron and no
alumina so - if boron is suitable for making oil spots - it would be the
best choice - Keep the ball clay around 10% and adjust the SiO2 so the
ratio is the same.
You should also consider upping the MgO as well - all the above will raise
expansion and perhaps lead to crazing - the MgO in the dolomite will help
keep the expansion down.
You are sooooo right - This is sooooo much fun - what a great way to
describe how so many feel about calculation.
RR
>I am test firing my new kiln as I type and can't wait to try it with
>pots in it next. Problem is that I have been formulating and testing
>glazes for c10-11 Reduction until now and plan to fire this kiln to c6 ox.
>
>Anyway I want to check my work here:
>
>I have an Oil Spot (From an old CM I believe) which I like in the c10
>firing - It is especially nice in oxidation spots in that kiln though
>so I want to try it in my electric kiln.
>
>Original recipe:
>John's Oil Spot ^10-^11
>Dolomite .... 44
>Whiting ..... 44
>Kona F4 .....573
>EPK ......... 97
>Silica ......242
>Cobalt Carb . 50
>Iron Oxide . 80
>
>Looking at it with John H's GlazeMaster Program (Thank you John for a
>great piece of software!) and comparing it to Ron and John's ^6 limits
>the KNaO is High as is the Alumina and Silica - The KNaO I will ignore
>(as it is high for ^10 limits also) and look only at the Alumina and
>Silica for now. Looks like I can delete the EPK and lower the Silica to
>about 100 and be ok. Does that look resonable to you people? I hope to
>fire this week so I thought I would try both the original ^10 glaze
>which I have already mixed and a reformulated version.
>
>This is sooooo much fun!
>Cheers!
>Linda
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
David Hewitt on wed 4 jun 03
Linda,
I would be surprised if you manage to find a good oil spot at cone. If
you do then please share it with us.
My experience with oil spot glazes has been in oxidation at cone 9. I
fund it best on a porcelain body. If you are interested in the recipe,
please contact me.
I was also involved in oil spot glazes with Mike Bailey back in 1994
when we did some tests for Ceramic Review (published in CR147 May/June
1994). Copies are not now available from Ceramic Review, but if you wish
I can send you a copy by email attachment.
The essence of the article is that, based on a number if different oil
spot recipes, that you need to have the % mol parts in the following
range:-
basic oxides 13-17 % mol parts
amphoteric oxides 14-18 % mol parts
acidic oxides 67-70 % mol parts
These were all cone 9 in oxidation.
David
In message , Linda Knapp writes
>I am test firing my new kiln as I type and can't wait to try it with
>pots in it next. Problem is that I have been formulating and testing
>glazes for c10-11 Reduction until now and plan to fire this kiln to c6 ox.
>
>Anyway I want to check my work here:
>
>I have an Oil Spot (From an old CM I believe) which I like in the c10
>firing - It is especially nice in oxidation spots in that kiln though
>so I want to try it in my electric kiln.
>
>Original recipe:
>John's Oil Spot ^10-^11
>Dolomite .... 44
>Whiting ..... 44
>Kona F4 .....573
>EPK ......... 97
>Silica ......242
>Cobalt Carb . 50
>Iron Oxide . 80
>
>Looking at it with John H's GlazeMaster Program (Thank you John for a
>great piece of software!) and comparing it to Ron and John's ^6 limits
>the KNaO is High as is the Alumina and Silica - The KNaO I will ignore
>(as it is high for ^10 limits also) and look only at the Alumina and
>Silica for now. Looks like I can delete the EPK and lower the Silica to
>about 100 and be ok. Does that look resonable to you people? I hope to
>fire this week so I thought I would try both the original ^10 glaze
>which I have already mixed and a reformulated version.
>
>This is sooooo much fun!
>Cheers!
>Linda
--
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
Fraser Forsythe on wed 4 jun 03
Ron's observation can save converts a LOT of time and
frustration!
I spent a long time trying to duplicate a semi-matt
c11 at c6. It was a very nice semi-matt white, both
fired in reduction. Got the melt in one trial with my
program. But (after far too long) it occurred to me
that I wasn't getting the visual (crystal formation)
because of the ramp down, esp. during the crystal
formation zone.
There are some things you learn that should be
tattooed on a prominent surface. This is one. Thanks
for mentioning this Ron.
Fraser
--- Ron Roy wrote: > A few years
ago I might have agreed with this but I
> think there is another
> factor that has been completely overlooked until
> recently.
>
> Most high fire kilns cool slower than electric kilns
> and that slower
> cooling has a profound effect on glazes.
>
> When trying to duplicate cone 10 glazes at cone 6 it
> is important to know
> how fast (how slow) they cooled in the gas kiln.
> Trying to duplicate that
> cycle is probably crucial to maximize chances of
> success.
>
> Perhaps I should include an example of why I think
> this - at the risk of
> someone complaining about plugging our book.
>
> When showing test tiles of some of our glazes to
> experienced potters - John
> said they did not believe they were not fired in
> reduction. I have to admit
> - I have seen very few cone 6 glazes that break up
> so well over raised
> decoration and edges. Most cone 6 glazes that act
> that way are over fluxed
> to the point where the glaze is actually moving into
> the clay looking for
> silica to melt. Those types of glazes are not
> durable because they don't
> have enough silica and/or alumina.
>
> Our glazes are balanced, durable glazes with plenty
> of silica and alumina -
> try them with a regular cool down in most electric
> kilns and they become
> quite ordinary - nice enough but not any where as
> interesting as with a
> slower cooling.
>
> So I am now not so sure that it the reduction that
> makes all the difference
> - the iron spotting yes - the particular colours
> from reduction - yes - but
> the formation of crystals from slower cooling - no.
>
> RR
>
>
> >Most people who switch from high-fire reduction to
> mid-range oxidation don't
> >realize that the atmosphere switch makes more
> difference than the
> >temperature switch.
>
> 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@pclink.com.
=====
Fraser Forsythe
fraser@glazeexchange.com
Guelph,Canada
______________________________________________________________________
Post your free ad now! http://personals.yahoo.ca
Brian Haviland on thu 5 jun 03
Ron
Is this why I am having trouble with wax wing brown ?? I always
end up with a greenish colored glaze.I thought that it was mostly due to
the difference in the source of my glaze components. Same name different
mine ???? I have a l&l kiln that i can ramp down slowly. Do you think this
will be my answer. I bought your book and It has really helped me
understand ^6 glazes.(plug,plug,plug). Thank you (and jon) for sharing your
knowledge and making glazes less frustrating for us newbies.
Brian Haviland
At 11:12 PM 6/3/03 -0500, you wrote:
>Most high fire kilns cool slower than electric kilns and that slower
>cooling has a profound effect on glazes.
>
>When trying to duplicate cone 10 glazes at cone 6 it is important to know
>how fast (how slow) they cooled in the gas kiln. Trying to duplicate that
>cycle is probably crucial to maximize chances of success.
>
>Our glazes are balanced, durable glazes with plenty of silica and alumina -
>try them with a regular cool down in most electric kilns and they become
>quite ordinary - nice enough but not any where as interesting as with a
>slower cooling.
>
>
>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@pclink.com.
John Hesselberth on thu 5 jun 03
Hi Brian,
Ron is traveling and is logged off Clayart temporarily. If you are not
controlling your cooling rate, however, I urge you to give it a try. I
am not sure what rapidly cooled Waxwing will look like--but I bet it
will be quite different from that cooled the way we recommend.
Thanks for the plugs.
Regards,
John
On Thursday, June 5, 2003, at 07:28 AM, Brian Haviland wrote:
> Ron
>
> Is this why I am having trouble with wax wing brown ?? I always
> end up with a greenish colored glaze.I thought that it was mostly due
> to
> the difference in the source of my glaze components. Same name
> different
> mine ???? I have a l&l kiln that i can ramp down slowly. Do you think
> this
> will be my answer. I bought your book and It has really helped me
> understand ^6 glazes.(plug,plug,plug). Thank you (and jon) for sharing
> your
> knowledge and making glazes less frustrating for us newbies.
>
> Brian Haviland
camoore on fri 6 jun 03
John,
I have seen fast-cooled Waxwing: it goes khaki-greenish.
Charles
Sacramento
----- Original Message -----
From: "John Hesselberth"
To:
Sent: Thursday, June 05, 2003 1:39 PM
Subject: Re: Glaze Gurus: c10 to c6
> Hi Brian,
>
> Ron is traveling and is logged off Clayart temporarily. If you are not
> controlling your cooling rate, however, I urge you to give it a try. I
> am not sure what rapidly cooled Waxwing will look like--but I bet it
> will be quite different from that cooled the way we recommend.
>
> Thanks for the plugs.
>
> Regards,
>
> John
> On Thursday, June 5, 2003, at 07:28 AM, Brian Haviland wrote:
>
> > Ron
> >
> > Is this why I am having trouble with wax wing brown ?? I always
> > end up with a greenish colored glaze.I thought that it was mostly due
> > to
> > the difference in the source of my glaze components. Same name
> > different
> > mine ???? I have a l&l kiln that i can ramp down slowly. Do you think
> > this
> > will be my answer. I bought your book and It has really helped me
> > understand ^6 glazes.(plug,plug,plug). Thank you (and jon) for sharing
> > your
> > knowledge and making glazes less frustrating for us newbies.
> >
> > Brian Haviland
>
>
____________________________________________________________________________
__
> 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.
| |
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