Tom Schoonover on sun 6 may 07
Hello,
for the past 4 months, i have been experiencing a bag glaze problem. I fire to cone 6 in an
electric kiln. for 4 years, i have been using only 2 glazes, a green chun and an alberta yellow
glaze. all of a sudden, one day, i opened my kiln, and the yellow glaze had an awful green haze
showing where the glaze was a little thicker. so first i thought my yellow glaze was contaminated
by the green, i mixed a new batch, and the same thing happened. Then I changed the elements in
my kiln, the the thermocoupe, and the vent motor. I have checked to make sure there is a strong
pull out of the vent. I feel like i have a brand new kiln, and my problem is still happening. i have
tried anything possible that made some kind of sense to me. please help me.
Kristin schoonover
John and Judy Hesselberth on mon 7 may 07
On May 6, 2007, at 7:05 PM, Tom Schoonover wrote:
> Hello,
>
> for the past 4 months, i have been experiencing a bag glaze
> problem. I fire to cone 6 in an
> electric kiln. for 4 years, i have been using only 2 glazes, a
> green chun and an alberta yellow
> glaze. all of a sudden, one day, i opened my kiln, and the yellow
> glaze had an awful green haze
> showing where the glaze was a little thicker. so first i thought
> my yellow glaze was contaminated
> by the green, i mixed a new batch, and the same thing happened.
> Then I changed the elements in
> my kiln, the the thermocoupe, and the vent motor. I have checked
> to make sure there is a strong
> pull out of the vent. I feel like i have a brand new kiln, and my
> problem is still happening. i have
> tried anything possible that made some kind of sense to me. please
> help me.
> Kristin schoonover
Hi Kristin,
First tell us what your witness cones are telling you. Are they
indicating a true cone 6 firing? You didn't say whether you are
firing by computer or manual control and a kiln sitter, but both of
those things can go bad or get out of calibration. It is important to
always have at least some cones in the kiln. They are the 'gold
standard'.
If your cones are saying you are at a true cone 6, then you may have
had an ingredient change or a mixup in ingredients sent to you by
your supplier. What ingredients have you ordered recently? Suppliers
do occasionally get the wrong thing in the bag. Also ingredients like
Gerstley Borate (and others) change composition over time.
So give us a little more information on the above items and maybe one
of us will be able to help.
Regards,
John
William & Susan Schran User on mon 7 may 07
On 5/6/07 7:05 PM, "Tom Schoonover" wrote:
> for the past 4 months, i have been experiencing a bag glaze problem. I fire
> to cone 6 in an
> electric kiln. for 4 years, i have been using only 2 glazes, a green chun and
> an alberta yellow
> glaze. all of a sudden, one day, i opened my kiln, and the yellow glaze had
> an awful green haze
> showing where the glaze was a little thicker. so first i thought my yellow
> glaze was contaminated
> by the green, i mixed a new batch, and the same thing happened.
I doubt the things you changed on the kiln had anything to do with the glaze
change.
You didn't mention - do you use witness cones?
If you are using the kiln sitter or a program to fire, either could be off.
But I do think your problem may be with a material in the glaze.
When the glaze changed, had you mixed a new batch?
Did you recently purchase any new materials that are a component of this
glaze? Are any of the new materials form a different supplier?
Those would be my first suspects.
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Tom Schoonover on mon 7 may 07
in addition to the info i wrote first, I have found that the less I pack in the kiln, the less the green
haze happens. So the more air flow, the better. I have checked the vent to make sure there aren't
any leaks happening. So the haze isn't as dark, but it occurs in recessed areas, like the inside of
casserole dishes, or inside planters. any suggestions???
Lynn Goodman Porcelain Pottery on mon 7 may 07
On May 6, 2007, at 7:05 PM, Tom Schoonover wrote:
> Hello,
>
> for the past 4 months, i have been experiencing a bag glaze
> problem. I fire to cone 6 in an
> electric kiln. for 4 years, i have been using only 2 glazes, a
> green chun and an alberta yellow
> glaze. all of a sudden, one day, i opened my kiln, and the yellow
> glaze had an awful green haze
> showing where the glaze was a little thicker.
Hi Kristin,
It sounds to me like one of your materials has changed. Is there
gerstley borate in your glaze? It's notorious for changing from bag
to bag (I took it out of my recipes and switched to frit for this
very reason). Ask your ceramic supplier if there is info on both the
previous bag and the current bag, then compare what has changed; you
should be able to get it back to what it was.
Lynn
Lynn Goodman
Fine Porcelain Pottery
Cell 347-526-9805
www.lynngoodmanporcelain.com
Tom Schoonover on mon 7 may 07
i'm sorry i didn't give enough specifics. I did have
cones in the kiln, all came up like a true cone 6
firing. I have an electronic control, and used a
basic medium speed cone 6 program. These are all
things I have been doing for 4 years. everything was
working fine, i just got a glaze load out that
worked like normal. then the next firing, using the
same exact glaze batches, wax resist, and
firing schedule, the green haze appeared. The haze
seems to appear where the glaze was brushed
on a little thicker. I can see brush strokes a little
bit. So i tried thinning down the glaze, but it
doesn't look as nice and yellow as it did in the past,
and some of the haze does show up. I did a
test fire, with many different applications. I dipped
the yellow thin and thick. I brushed it on, and
used wax on it and not. I put these test pieces in
the kiln by themselves, so the kiln was super
empty. Every piece came out fine. then the next
time, i did everything like before, and it
happened again. Since then, I have fired to cone 6,
but left the kiln more than half empty, with
plenty of room to allow air flow around each piece.
this has helped a lot. but still, when there are
pieces, like a planter, or casserole, with the yellow
glaze deep on the inside, the yellow goes hazey
green again, and the outside would look ok. I am
stumped. This all makes me want to believe it
could be a problem with the kiln.
my glazes are:
Alberta yellow
gerstly, neph sye, alberta, silica, and soda ash
the green glaze is:
f4, whiting, zinc oxide, om4 and flint, with 3.5%
copper carb.
Is it possible that the copper is affecting the
yellow, who knows!!! any answers.......
--- William & Susan Schran User
wrote:
> On 5/6/07 7:05 PM, "Tom Schoonover"
> wrote:
>
> > for the past 4 months, i have been experiencing a
> bag glaze problem. I fire
> > to cone 6 in an
> > electric kiln. for 4 years, i have been using
> only 2 glazes, a green chun and
> > an alberta yellow
> > glaze. all of a sudden, one day, i opened my
> kiln, and the yellow glaze had
> > an awful green haze
> > showing where the glaze was a little thicker. so
> first i thought my yellow
> > glaze was contaminated
> > by the green, i mixed a new batch, and the same
> thing happened.
>
> I doubt the things you changed on the kiln had
> anything to do with the glaze
> change.
> You didn't mention - do you use witness cones?
> If you are using the kiln sitter or a program to
> fire, either could be off.
>
> But I do think your problem may be with a material
> in the glaze.
> When the glaze changed, had you mixed a new batch?
> Did you recently purchase any new materials that are
> a component of this
> glaze? Are any of the new materials form a different
> supplier?
>
> Those would be my first suspects.
>
>
> --
> William "Bill" Schran
> wschran@cox.net
> wschran@nvcc.edu
> http://www.creativecreekartisans.com
>
>
______________________________________________________________________________
> 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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Tom Schoonover on mon 7 may 07
i'm sorry i didn't give enough specifics. I did have
cones in the kiln, all came up like a true cone 6
firing. I have an electronic control, and used a
basic medium speed cone 6 program. These are all
things I have been doing for 4 years. everything was
working fine, i just got a glaze load out that
worked like normal. then the next firing, using the
same exact glaze batches, wax resist, and
firing schedule, the green haze appeared. The haze
seems to appear where the glaze was brushed
on a little thicker. I can see brush strokes a little
bit. So i tried thinning down the glaze, but it
doesn't look as nice and yellow as it did in the past,
and some of the haze does show up. I did a
test fire, with many different applications. I dipped
the yellow thin and thick. I brushed it on, and
used wax on it and not. I put these test pieces in
the kiln by themselves, so the kiln was super
empty. Every piece came out fine. then the next
time, i did everything like before, and it
happened again. Since then, I have fired to cone 6,
but left the kiln more than half empty, with
plenty of room to allow air flow around each piece.
this has helped a lot. but still, when there are
pieces, like a planter, or casserole, with the yellow
glaze deep on the inside, the yellow goes hazey
green again, and the outside would look ok. I am
stumped. This all makes me want to believe it
could be a problem with the kiln.
my glazes are:
Alberta yellow
gerstly, neph sye, alberta, silica, and soda ash
the green glaze is:
f4, whiting, zinc oxide, om4 and flint, with 3.5%
copper carb.
Is it possible that the copper is affecting the
yellow, who knows!!! any answers.......
--- John and Judy Hesselberth
wrote:
> On May 6, 2007, at 7:05 PM, Tom Schoonover wrote:
>
> > Hello,
> >
> > for the past 4 months, i have been experiencing a
> bag glaze
> > problem. I fire to cone 6 in an
> > electric kiln. for 4 years, i have been using
> only 2 glazes, a
> > green chun and an alberta yellow
> > glaze. all of a sudden, one day, i opened my
> kiln, and the yellow
> > glaze had an awful green haze
> > showing where the glaze was a little thicker. so
> first i thought
> > my yellow glaze was contaminated
> > by the green, i mixed a new batch, and the same
> thing happened.
> > Then I changed the elements in
> > my kiln, the the thermocoupe, and the vent motor.
> I have checked
> > to make sure there is a strong
> > pull out of the vent. I feel like i have a brand
> new kiln, and my
> > problem is still happening. i have
> > tried anything possible that made some kind of
> sense to me. please
> > help me.
> > Kristin schoonover
>
> Hi Kristin,
>
> First tell us what your witness cones are telling
> you. Are they
> indicating a true cone 6 firing? You didn't say
> whether you are
> firing by computer or manual control and a kiln
> sitter, but both of
> those things can go bad or get out of calibration.
> It is important to
> always have at least some cones in the kiln. They
> are the 'gold
> standard'.
>
> If your cones are saying you are at a true cone 6,
> then you may have
> had an ingredient change or a mixup in ingredients
> sent to you by
> your supplier. What ingredients have you ordered
> recently? Suppliers
> do occasionally get the wrong thing in the bag. Also
> ingredients like
> Gerstley Borate (and others) change composition over
> time.
>
> So give us a little more information on the above
> items and maybe one
> of us will be able to help.
>
> Regards,
>
> John
>
>
______________________________________________________________________________
> 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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Tom Schoonover on mon 7 may 07
i'm sorry i didn't give enough specifics. I did have cones in the kiln, all came up like a true cone 6
firing. I have an electronic control, and used a basic medium speed cone 6 program. These are all
things I have been doing for 4 years. everything was working fine, i just got a glaze load out that
worked like normal. then the next firing, using the same exact glaze batches, wax resist, and
firing schedule, the green haze appeared. The haze seems to appear where the glaze was brushed
on a little thicker. I can see brush strokes a little bit. So i tried thinning down the glaze, but it
doesn't look as nice and yellow as it did in the past, and some of the haze does show up. I did a
test fire, with many different applications. I dipped the yellow thin and thick. I brushed it on, and
used wax on it and not. I put these test pieces in the kiln by themselves, so the kiln was super
empty. Every piece came out fine. then the next time, i did everything like before, and it
happened again. Since then, I have fired to cone 6, but left the kiln more than half empty, with
plenty of room to allow air flow around each piece. this has helped a lot. but still, when there are
pieces, like a planter, or casserole, with the yellow glaze deep on the inside, the yellow goes hazey
green again, and the outside would look ok. I am stumped. This all makes me want to believe it
could be a problem with the kiln.
my glazes are:
Alberta yellow
gerstly, neph sye, alberta, silica, and soda ash
the green glaze is:
f4, whiting, zinc oxide, om4 and flint, with 3.5% copper carb.
Is it possible that the copper is affecting the yellow, who knows!!! any answers.......
John and Judy Hesselberth on tue 8 may 07
On May 7, 2007, at 7:31 PM, Tom Schoonover wrote:
> i'm sorry i didn't give enough specifics. I did have
> cones in the kiln, all came up like a true cone 6
> firing. I have an electronic control, and used a
> basic medium speed cone 6 program. These are all
> things I have been doing for 4 years. everything was
> working fine, i just got a glaze load out that
> worked like normal. then the next firing, using the
> same exact glaze batches, wax resist, and
> firing schedule, the green haze appeared.
Hi Kristin,
Well this is a tough one. Sounds like you are doing everything as
right as it can be done. I am focusing on your experiments where you
fired in an almost empty kiln. While that can give you better
oxidation it can also affect your temperature profile and heating
rate as well as your cooling rate. In spite of your cones looking the
same the peak temperature and/or the time at peak temperature might
have been very slightly different--maybe only 5-10 degrees such that
it might not be obvious from your cones. Try adding 10 minutes to
your soak at peak temperature.
Also is there any change in the way you cool the kiln? For example,
have you added a piece of insulation on the lid (or anywhere else) to
try to save a little energy? Or have you started turning your vent
fan off during cooling? Anything that could slow down the cooling
might result in some crystals re-precipitating on the surface and
give you a haze like you describe.
Almost empty kilns will also cool more rapidly unless you are doing a
controlled "fire-down". Also the fact that you are seeing the haze
"deep on the inside" of your casserole points to either insufficient
heating or too slow cooling. I am making the assumption here that
this is a glossy transparent glaze and that is the way you want it
to be.
As I think about it while writing, I think the odds are higher that
your cooling rate has changed instead of your top temperature being a
little low--but you are in a better position to think that through
than I.
I hope this helps you find the answer,
John
Tom Schoonover on tue 8 may 07
hi john,
thank you for your ideas. I don't think that it is
being under fired or overfired, because in the past it
has happened. if it was underfired, it was pasty, and
over fired worked fine. the haze is an ugly green,
still transparent, but unwanted, the glazes are both
glossy, and transparent. Thank you, I will check the
cooling.
THank you,
Kristin
--- John and Judy Hesselberth
wrote:
> On May 7, 2007, at 7:31 PM, Tom Schoonover wrote:
>
> > i'm sorry i didn't give enough specifics. I did
> have
> > cones in the kiln, all came up like a true cone 6
> > firing. I have an electronic control, and used a
> > basic medium speed cone 6 program. These are all
> > things I have been doing for 4 years. everything
> was
> > working fine, i just got a glaze load out that
> > worked like normal. then the next firing, using
> the
> > same exact glaze batches, wax resist, and
> > firing schedule, the green haze appeared.
>
> Hi Kristin,
>
> Well this is a tough one. Sounds like you are doing
> everything as
> right as it can be done. I am focusing on your
> experiments where you
> fired in an almost empty kiln. While that can give
> you better
> oxidation it can also affect your temperature
> profile and heating
> rate as well as your cooling rate. In spite of your
> cones looking the
> same the peak temperature and/or the time at peak
> temperature might
> have been very slightly different--maybe only 5-10
> degrees such that
> it might not be obvious from your cones. Try adding
> 10 minutes to
> your soak at peak temperature.
>
> Also is there any change in the way you cool the
> kiln? For example,
> have you added a piece of insulation on the lid (or
> anywhere else) to
> try to save a little energy? Or have you started
> turning your vent
> fan off during cooling? Anything that could slow
> down the cooling
> might result in some crystals re-precipitating on
> the surface and
> give you a haze like you describe.
>
> Almost empty kilns will also cool more rapidly
> unless you are doing a
> controlled "fire-down". Also the fact that you are
> seeing the haze
> "deep on the inside" of your casserole points to
> either insufficient
> heating or too slow cooling. I am making the
> assumption here that
> this is a glossy transparent glaze and that is the
> way you want it
> to be.
>
> As I think about it while writing, I think the odds
> are higher that
> your cooling rate has changed instead of your top
> temperature being a
> little low--but you are in a better position to
> think that through
> than I.
>
> I hope this helps you find the answer,
>
> John
>
>
______________________________________________________________________________
> 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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William & Susan Schran User on tue 8 may 07
On 5/7/07 8:29 PM, "Tom Schoonover" wrote:
> Since then, I have fired to cone 6, but left the kiln more than half empty,
> with
> plenty of room to allow air flow around each piece. this has helped a lot.
> but still, when there are
> pieces, like a planter, or casserole, with the yellow glaze deep on the
> inside, the yellow goes hazey
> green again, and the outside would look ok. I am stumped. This all makes me
> want to believe it
> could be a problem with the kiln.
> my glazes are:
> Alberta yellow
> gerstly, neph sye, alberta, silica, and soda ash
There are so many variables in just this snippet of information that it may
take some time to figure out exactly what's causing changes.
Certainly changing the density of the load will affect heating and cooling.
Did the kiln heat and cool faster than before?
The yellow glaze contains gertsley borate - certainly this can play a factor
due to continuous changes in chemistry - perhaps changing to a frit - 3195?
The soda ash is soluble so the glaze can change over time as it sits.
Just some things to think about.
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
D Kat on tue 8 may 07
--- In clayart@yahoogroups.com, Tom Schoonover wrote:
>
> Hello,
>
> for the past 4 months, i have been experiencing a bag glaze
problem. I fire to cone 6 in an
> electric kiln. for 4 years, i have been using only 2 glazes, a
green chun and an alberta yellow
> glaze. all of a sudden, one day, i opened my kiln, and the yellow
glaze had an awful green haze
> showing where the glaze was a little thicker. so first i thought
my yellow glaze was contaminated
> by the green, i mixed a new batch, and the same thing happened.
Then I changed the elements in
> my kiln, the the thermocoupe, and the vent motor. I have checked
to make sure there is a strong
> pull out of the vent. I feel like i have a brand new kiln, and my
problem is still happening. i have
> tried anything possible that made some kind of sense to me. please
help me.
> Kristin schoonover
>
What are the ingredients in the yellow glaze (I'm assuming it isn't
fuming from the green since you said it was on the inside of a
casserole dish)?
Donna
Tom Schoonover on wed 9 may 07
hi donna
the yellow has gerstly, neph sye, alberta slip, silica
and soda ash. the other glaze i use does have 3.5
copper carb. at this point i am assuming it may be
fuming, because it doesn't happen on every piece, only
the ones or areas with bad air flow.
any help...? kristin
--- D Kat wrote:
> --- In clayart@yahoogroups.com, Tom Schoonover
> wrote:
> >
> > Hello,
> >
> > for the past 4 months, i have been experiencing a
> bag glaze
> problem. I fire to cone 6 in an
> > electric kiln. for 4 years, i have been using
> only 2 glazes, a
> green chun and an alberta yellow
> > glaze. all of a sudden, one day, i opened my
> kiln, and the yellow
> glaze had an awful green haze
> > showing where the glaze was a little thicker. so
> first i thought
> my yellow glaze was contaminated
> > by the green, i mixed a new batch, and the same
> thing happened.
> Then I changed the elements in
> > my kiln, the the thermocoupe, and the vent motor.
> I have checked
> to make sure there is a strong
> > pull out of the vent. I feel like i have a brand
> new kiln, and my
> problem is still happening. i have
> > tried anything possible that made some kind of
> sense to me. please
> help me.
> > Kristin schoonover
> >
>
> What are the ingredients in the yellow glaze (I'm
> assuming it isn't
> fuming from the green since you said it was on the
> inside of a
> casserole dish)?
> Donna
>
>
______________________________________________________________________________
> 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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dwichman@frontiernet.net on wed 9 may 07
....................
""i'm sorry i didn't give enough specifics. I did have
cones in the kiln, all came up like a true cone 6
firing. I have an electronic control, and used a
basic medium speed cone 6 program. These are all
things I have been doing for 4 years. everything was
working fine, i just got a glaze load out that
worked like normal. then the next firing, using the
same exact glaze batches, wax resist, and
firing schedule, the green haze appeared.""
.....................
I am no expert, but have noted some of my glazes look drastically
different even on different white stoneware clays. Were you using
the same clay as always and probably the same thickness? Just an
idea.....
Debi Wichman
Cookeville, TN
http://www.elementterra.com
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