Cindy Strnad on sun 11 nov 01
I am liking weathered bronze green more and more.
Though I only use it outside and on decorative
pieces, the pinholes are beginning to bug me. I
get them on clean, soaked bisque, thick or thin
glaze, slow cool, with a long soak at peak temp,
with a short soak at peak temp . . . well, you get
the picture. I'd like to start using it on pieces
for sale if I can solve this problem without
changing the appearance too much. Any suggestions?
Weathered Bronze Green ^6
Pete Pinnell
=======================================
LITHIUM CARBONATE... 1.00 0.91%
STRONTIUM CARBONATE. 20.00 18.18%
NEPHELINE SYENITE... 60.00 54.55%
OM #4 BALL CLAY..... 10.00 9.09%
FLINT............... 9.00 8.18%
TITANIUM DIOXIDE.... 5.00 4.55%
*Copper Carbonate.... 5.00 4.55%
========
110.00
CaO 0.03* 0.57%
Li2O 0.05* 0.42%
MgO 0.00* 0.06%
K2O 0.11* 3.09%
Na2O 0.35* 6.63%
SrO 0.46* 14.49%
TiO2 0.22 5.29%
Al2O3 0.56 17.50%
SiO2 2.82 51.79%
Fe2O3 0.00 0.16%
Cost/kg 0.68
Si:Al 5.02
SiB:Al 5.02
Expan 9.28
Thanks,
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
cindy@earthen-vessels-pottery.com
http://www.earthen-vessels-pottery.com
Tom Wirt/Betsy Price on mon 12 nov 01
I'm going to step way out on a limb here. I mentioned the clay/glaze
interface here yesterday.
We have had serious pitting, pinholing and cratering problems for much
of this year when we switched from an unbalanced clay to a balanced
one. Balanced here implies that the one we switched from was way
over-fluxed as witnessed by slumping, bloating when overfired by a
cone and zero absorption on test bars.
The glazes we have had trouble with are generally short of silica. My
hypothesis is that the clay and glaze interact with each other. If
the glaze is short of silica, it tries to suck it from the clay or if
it is short of flux, it starves the surface of the clay. Either way,
you don't get a full melt of the glaze and thus any ingredients that
are boiling or outgassing at maturity will tend to freeze rather than
heal over as they would if there was enough flux and/or silica.
This same effect could easily happen where grog is the culprit, not
adding enough flux to the clay/glaze interface and/or starving the
glaze. This can be examined with a low power magnifier to see what's
at the bottom of the pinhole/crater.
Anyone else care to take a shot at this?
Tom Wirt
From: "Cl Litman"
Subject: Re: Weathered Bronze Green
| I've been firing this glaze to cone 6 for a long time and only
started
| seeing pinholes regularly when I stopped using white stoneware with
no
| grog. Get pinholes with the same firing schedule on all darker
clays
| which all have varying amounts of grog. Ideas?
|
Dannon Rhudy on mon 12 nov 01
At 09:00 PM 11/11/01 -0700, you wrote:
>I am liking weathered bronze green ...
pinholes are beginning to bug me. Any suggestions?......
Cindy, this glaze is made to fire through a
very long temperature range. We routinely
fire it to 9/10 here. No pinholes. It
may be that it just needs a bit more heat,
though I have fired it to ^6 oxidation without
problems. Maybe it is a claybody/interface
problem. When you say "pinholes" do you
mean a plague of them, or just the odd one
here or there?
regards
Dannon Rhudy
Sherri Grossbauer on mon 12 nov 01
Cindy-
I, too, love Pinnell's Weathered Bronze glaze. Buy I don't seem to have the
pinhole problem, so maybe it's your claybody. I have used ^6 porcelain-type
clay as well as a heavily grogged ^6 clay.
Just a suggestion.
Sherri
Mud Club Pottery
Ababi on mon 12 nov 01
Hello Cindy
I had didferent problems with this glaze. I think my soulutions are
twice.
THICK aplication
Porcealain. It turned the best on the porcelain that Tom buck made for
me. Otherwise I had to fire and sometimes refire
Tom had made it for me when I could not buy plastic kaolin and I needed
a kaolaine claybody for ^6
I will add it here perhaps you want to try it or change it acording to
your needs
Ababi
Ababi's ^6 Porcelianous by Tom Buck
===================================
BALL CLAY (AK)...... 48.00 47.06%
ENGLISH KAOLIN CC31. 33.00 32.35% Use EPK
NEPHELINE SYENITE... 14.00 13.73%
ALUMINA HYDRATE..... 5.00 4.90% I could not find at that time
Molochite perhaps can be changed too.
BENTONITE........... 2.00 1.96%
========
102.00
CaO 0.04* 0.17%
MgO 0.37* 1.24%
K2O 0.27* 2.06%
Na2O 0.32* 1.65%
TiO2 0.01 0.09%
Al2O3 4.58 38.33%
SiO2 11.25 55.55%
Fe2O3 0.07 0.92%
Text1 5.19
Si:Al 2.46
SiB:Al 2.46
Expan 5.86
Untitled Recipe 1
=================
BALL CLAY (AK)...... 1.00 100.00%
========
1.00
CaO 0.06* 0.23%
MgO 0.89* 2.53%
K2O 0.05* 0.34%
TiO2 0.02 0.11%
Al2O3 5.24 37.66%
SiO2 13.70 57.98%
Fe2O3 0.10 1.15%
Text1 3.66
Si:Al 2.61
SiB:Al 2.61
Expan 4.78
LOI 11.70
---------- Original Message ----------
>I am liking weathered bronze green more and more.
>Though I only use it outside and on decorative
>pieces, the pinholes are beginning to bug me. I
>get them on clean, soaked bisque, thick or thin
>glaze, slow cool, with a long soak at peak temp,
>with a short soak at peak temp . . . well, you get
>the picture. I'd like to start using it on pieces
>for sale if I can solve this problem without
>changing the appearance too much. Any suggestions?
>Weathered Bronze Green ^6
>Pete Pinnell
>=======================================
> LITHIUM CARBONATE... 1.00 0.91%
> STRONTIUM CARBONATE. 20.00 18.18%
> NEPHELINE SYENITE... 60.00 54.55%
> OM #4 BALL CLAY..... 10.00 9.09%
> FLINT............... 9.00 8.18%
> TITANIUM DIOXIDE.... 5.00 4.55%
>*Copper Carbonate.... 5.00 4.55%
> ========
> 110.00
> CaO 0.03* 0.57%
> Li2O 0.05* 0.42%
> MgO 0.00* 0.06%
> K2O 0.11* 3.09%
> Na2O 0.35* 6.63%
> SrO 0.46* 14.49%
> TiO2 0.22 5.29%
> Al2O3 0.56 17.50%
> SiO2 2.82 51.79%
> Fe2O3 0.00 0.16%
> Cost/kg 0.68
> Si:Al 5.02
> SiB:Al 5.02
> Expan 9.28
>Thanks,
>Cindy Strnad
Paul Lewing on mon 12 nov 01
Cindy,
I think the problem is the titanium. I'd try cutting that down and see how
little you can get away with and still maintain the look you like. And I'd
try also replacing some or all of the titanium with some zirconium
opacifier to see if you could get the same look that way.
Paul Lewing, Seattle
Cl Litman on mon 12 nov 01
I've been firing this glaze to cone 6 for a long time and only started
seeing pinholes regularly when I stopped using white stoneware with no
grog. Get pinholes with the same firing schedule on all darker clays
which all have varying amounts of grog. Ideas?
Cheryl Litman - NJ
cheryllitman@juno.com
On Mon, 12 Nov 2001 10:05:55 -0600 Dannon Rhudy
writes:
> At 09:00 PM 11/11/01 -0700, you wrote:
> >I am liking weathered bronze green ...
> pinholes are beginning to bug me. Any suggestions?......
>
> Cindy, this glaze is made to fire through a
> very long temperature range. We routinely
> fire it to 9/10 here. No pinholes. It
> may be that it just needs a bit more heat,
> though I have fired it to ^6 oxidation without
> problems. Maybe it is a claybody/interface
> problem. When you say "pinholes" do you
> mean a plague of them, or just the odd one
> here or there?
>
> regards
>
> Dannon Rhudy
>
>
_________________________________________________________________________
_____
> 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 mon 12 nov 01
Hi Cindy,
Yes, it does pinhole a little bit. I have speculated before that this glaze
is just barely melting at cone 6. It is really a cone 9-10 glaze that
happens to work and be fairly stable at cone 6. I would think another cone
higher might help the pinholes. If you don't want to do that I'd add just a
pinch or two of boron. The look might not change too much if you kept boron
to 0.1 or so. You've already tried thin--I would keep it as thin as you can
and still get good cover.
I have also tried this glaze as an overglaze on top of some of my other
glazes. It does some really neat things and if the underneath glaze is a
good melter it seems to pinhole less. One of these days I am really going
to explore strontium glazes. I think it has some properties we cone-sixers
would really like if we got to know it better.
Regards,
John
on 11/11/01 11:00 PM, Cindy Strnad at earthenv@GWTC.NET wrote:
> I am liking weathered bronze green more and more.
> Though I only use it outside and on decorative
> pieces, the pinholes are beginning to bug me. I
> get them on clean, soaked bisque, thick or thin
> glaze, slow cool, with a long soak at peak temp,
> with a short soak at peak temp . . . well, you get
> the picture. I'd like to start using it on pieces
> for sale if I can solve this problem without
> changing the appearance too much. Any suggestions?
>
> Weathered Bronze Green ^6
> Pete Pinnell
> =======================================
> LITHIUM CARBONATE... 1.00 0.91%
> STRONTIUM CARBONATE. 20.00 18.18%
> NEPHELINE SYENITE... 60.00 54.55%
> OM #4 BALL CLAY..... 10.00 9.09%
> FLINT............... 9.00 8.18%
> TITANIUM DIOXIDE.... 5.00 4.55%
> *Copper Carbonate.... 5.00 4.55%
> ========
> 110.00
>
> CaO 0.03* 0.57%
> Li2O 0.05* 0.42%
> MgO 0.00* 0.06%
> K2O 0.11* 3.09%
> Na2O 0.35* 6.63%
> SrO 0.46* 14.49%
> TiO2 0.22 5.29%
> Al2O3 0.56 17.50%
> SiO2 2.82 51.79%
> Fe2O3 0.00 0.16%
>
> Cost/kg 0.68
> Si:Al 5.02
> SiB:Al 5.02
> Expan 9.28
>
Web site: http://www.frogpondpottery.com Email: john@frogpondpottery.com
"The life so short, the craft so long to learn." Chaucer's translation of
Hippocrates, 5th cent. B.C.
Tom Wirt/Betsy Price on mon 12 nov 01
Hi Dannon....
I'm wondering if I ever replied to your note last summer....seems like
years ago.
Anyway, your note to Cindy spurred my interest if not my guilt. The
clay/glaze interface. That's where my theories ran to finally as to
what was causing all our problems this year.
What light can you shed on how this interface works? How does clay
affect glaze and vice versa? There is precious little written that I
have been able to find, including in the scientific papers listed in
ACERS. I have some theories, but haven't yet been able to run tests
to test them.
Tom Wirt
| >I am liking weathered bronze green ...
| pinholes are beginning to bug me. Any suggestions?......
|
| Cindy, this glaze is made to fire through a
| very long temperature range. We routinely
| fire it to 9/10 here. No pinholes. >> Maybe it is a
claybody/interface
| problem. When you say "pinholes" do you
| mean a plague of them, or just the odd one
| here or there?
|
Wanda Holmes on mon 12 nov 01
I do remember from an article Pete Pinnell wrote that he stressed "full cone
6 tip touching". He also suggests adding up to 3% more lithium if the
surface is too dry with some colorants. Could this improve the melt? Wanda
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of John Hesselberth
Sent: Monday, November 12, 2001 4:11 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Weathered Bronze Green
Hi Cindy,
Yes, it does pinhole a little bit. I have speculated before that this glaze
is just barely melting at cone 6. It is really a cone 9-10 glaze that
happens to work and be fairly stable at cone 6. I would think another cone
higher might help the pinholes. If you don't want to do that I'd add just a
pinch or two of boron. The look might not change too much if you kept boron
to 0.1 or so. You've already tried thin--I would keep it as thin as you can
and still get good cover.
I have also tried this glaze as an overglaze on top of some of my other
glazes. It does some really neat things and if the underneath glaze is a
good melter it seems to pinhole less. One of these days I am really going
to explore strontium glazes. I think it has some properties we cone-sixers
would really like if we got to know it better.
Regards,
John
on 11/11/01 11:00 PM, Cindy Strnad at earthenv@GWTC.NET wrote:
> I am liking weathered bronze green more and more.
> Though I only use it outside and on decorative
> pieces, the pinholes are beginning to bug me. I
> get them on clean, soaked bisque, thick or thin
> glaze, slow cool, with a long soak at peak temp,
> with a short soak at peak temp . . . well, you get
> the picture. I'd like to start using it on pieces
> for sale if I can solve this problem without
> changing the appearance too much. Any suggestions?
>
> Weathered Bronze Green ^6
> Pete Pinnell
> =======================================
> LITHIUM CARBONATE... 1.00 0.91%
> STRONTIUM CARBONATE. 20.00 18.18%
> NEPHELINE SYENITE... 60.00 54.55%
> OM #4 BALL CLAY..... 10.00 9.09%
> FLINT............... 9.00 8.18%
> TITANIUM DIOXIDE.... 5.00 4.55%
> *Copper Carbonate.... 5.00 4.55%
> ========
> 110.00
>
> CaO 0.03* 0.57%
> Li2O 0.05* 0.42%
> MgO 0.00* 0.06%
> K2O 0.11* 3.09%
> Na2O 0.35* 6.63%
> SrO 0.46* 14.49%
> TiO2 0.22 5.29%
> Al2O3 0.56 17.50%
> SiO2 2.82 51.79%
> Fe2O3 0.00 0.16%
>
> Cost/kg 0.68
> Si:Al 5.02
> SiB:Al 5.02
> Expan 9.28
>
Web site: http://www.frogpondpottery.com Email: john@frogpondpottery.com
"The life so short, the craft so long to learn." Chaucer's translation of
Hippocrates, 5th cent. B.C.
____________________________________________________________________________
__
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.
Wanda Holmes on mon 12 nov 01
Cindy,
I've tried it with 1% and 2% titanium and I have to say 5% produces a nicer
result. Lesser amounts don't give the nice mottling I get with 5%. I fire
this glaze on Clayword's Special Stoneware II, a cone 10 clay, smooth white,
no sand or grog. I fire to cone 6 (cone 7 just starting to bend) in an
electric kiln with a KilnMaster controller and an EnviroVent. My firing
cycle is relatively slow - about 10.5 hrs from start to finish and I hold at
the top temperature for 30 minutes. I don't get any pinholes.
I can give you the actual firing schedule if you think it would help.
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of Paul Lewing
Sent: Monday, November 12, 2001 4:56 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Weathered Bronze Green
Cindy,
I think the problem is the titanium. I'd try cutting that down and see how
little you can get away with and still maintain the look you like. And I'd
try also replacing some or all of the titanium with some zirconium
opacifier to see if you could get the same look that way.
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.
Ababi on tue 13 nov 01
Weathered bronze, as John has wrote, is a high fire glaze. It is among
these glazes that somehow, on the border, work in ^6 decoratively.
You must apply it thick, I apply it a few times, otherwise get dark
ugly brown.
I work now on another combination of glazes, might be a better
solution. the same feeling, but better on ^6.
If it will be you will be the first to know ( All 2871 of you or may be
more)
I don't belive that decreasing the titanium would help as I tried it
too. Again thicness, better on Kaolain(^6 porcelain)
Ababi
Snail Scott on tue 13 nov 01
>At 09:00 PM 11/11/01 -0700, you wrote:
>>I am liking weathered bronze green ...
> pinholes are beginning to bug me. Any suggestions?......
I don't know; I'm inept with glaze, and have plenty
of other problems, (evenness of coating is my bane)
but I've never had pinholes from this glaze. (I use
it on groggy buff stoneware in oxidation. I fire to
^6 with witness cones, then when the ^6 is at '9-oclock'
I turn all the switches to 'low' and set the timer for
three hours.)
-Snail
Doug Gray on tue 13 nov 01
Cindy,
I use that glaze frequently at cone 6 and cone 10 (now almost cone 11),
oxidation and reduction, but have not noticed the problem you
mentioned. Given the discussion that appeared on clayart several years
ago, I'm going to point a suspecting finger at the strontium. This
glaze has a significant amounts and not all strontium is the same. Some
is processed more coarsely and seems to have more difficulty melting
into the glaze mixture than other more refined forms. Have you recently
switched to a newer batch of strontium carb? You might try ball milling
your glaze before using. Or if that isn't possible, can you grind your
strontium with a mortar and pestle, another kitchen gadget gone awry.
I may be completely off base here, but I know I have gotten strontium
carb in the past that just didn't work in some glazes. And the matts
seem to be more finicky to this than most. I'm curious to see what the
experts have to say.
Doug, SC
Joan Ashworth on tue 13 nov 01
Cindy, I am experimenting both with Weathered Bronze Green and Opal Blue on
the same pot.
The WBG never pinholes - but I have replaced the ball clay with kaolin. I
have also reduced the titanium dioxide. I haven't the vaguest idea whether
this has made a difference to the pinholing problem. I remember an old post
about strontium, saying the change in grade in the US could be a
contributing factor to the pinholing. The suggestion was to brush over the
glaze once it had dried.
The most exciting of all is the WBG on the outside of a pot, and your opal
blue on the inside. In this situation OB becomes almost the same shade as
the WBG. (Volatility of the copper?????) And where they overlap on the
inside rim of the bowls there is sometimes a glossy black blue line......
beautiful.
Joan
in Durban
Ababi on wed 14 nov 01
Your letter reminds me: My supplier, when started to import strontium
carbonate chose to by it better grind ,smaller practicles. I know
people have complained about the powder does not pass the sieve.
Ababi
---------- Original Message ----------
>Cindy,
>I use that glaze frequently at cone 6 and cone 10 (now almost cone 11),
>oxidation and reduction, but have not noticed the problem you
>mentioned. Given the discussion that appeared on clayart several years
>ago, I'm going to point a suspecting finger at the strontium. This
>glaze has a significant amounts and not all strontium is the same. Some
>is processed more coarsely and seems to have more difficulty melting
>into the glaze mixture than other more refined forms. Have you recently
>switched to a newer batch of strontium carb? You might try ball milling
>your glaze before using. Or if that isn't possible, can you grind your
>strontium with a mortar and pestle, another kitchen gadget gone awry.
>I may be completely off base here, but I know I have gotten strontium
>carb in the past that just didn't work in some glazes. And the matts
>seem to be more finicky to this than most. I'm curious to see what the
>experts have to say.
>Doug, SC
Ron Roy on wed 14 nov 01
Make sure your bisque firing is clean, soak a bit and slow cool - and as
others have said - fire a bit higher.
You can also make the glaze less stiff by taking out 1% of the clay - or
maybe two - that will lower the temp of the glaze. You could also add 1%
whiting instead of taking out some clay or take out 1% clay and add 1%
whiting.
Just make sure you test any revisions before mixing up a big batch - try
500 grams - you can always add leftovers to your already mixed up batch.
RR
>I am liking weathered bronze green more and more.
>Though I only use it outside and on decorative
>pieces, the pinholes are beginning to bug me. I
>get them on clean, soaked bisque, thick or thin
>glaze, slow cool, with a long soak at peak temp,
>with a short soak at peak temp . . . well, you get
>the picture. I'd like to start using it on pieces
>for sale if I can solve this problem without
>changing the appearance too much. Any suggestions?
>
>Weathered Bronze Green ^6
>Pete Pinnell
>=======================================
> LITHIUM CARBONATE... 1.00 0.91%
> STRONTIUM CARBONATE. 20.00 18.18%
> NEPHELINE SYENITE... 60.00 54.55%
> OM #4 BALL CLAY..... 10.00 9.09%
> FLINT............... 9.00 8.18%
> TITANIUM DIOXIDE.... 5.00 4.55%
>*Copper Carbonate.... 5.00 4.55%
> ========
> 110.00
>
> CaO 0.03* 0.57%
> Li2O 0.05* 0.42%
> MgO 0.00* 0.06%
> K2O 0.11* 3.09%
> Na2O 0.35* 6.63%
> SrO 0.46* 14.49%
> TiO2 0.22 5.29%
> Al2O3 0.56 17.50%
> SiO2 2.82 51.79%
> Fe2O3 0.00 0.16%
>
> Cost/kg 0.68
> Si:Al 5.02
> SiB:Al 5.02
> Expan 9.28
>
>Thanks,
>
>Cindy Strnad
>Earthen Vessels Pottery
>RR 1, Box 51
>Custer, SD 57730
>USA
>cindy@earthen-vessels-pottery.com
>http://www.earthen-vessels-pottery.com
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
Pete Pinnell on wed 14 nov 01
Hi everyone,
I'm sorry I didn't pick up on his thread right away- my children very kindly shared a little virus with me and I've been out for a few days. I can think of several things that can make this glaze pinhole. They may have
already been suggested, but I haven't had time to go through my mail, so please forgive me if I repeat someone else's suggestion.
This is really a cone 9-10 glaze, and is at the very low end of its range at cone 6. In fact, without the copper it doesn't mature until about cone 7. Because of this, it's very sensitive to any outgassing from the clay, and
won't tend to heal. Taking it a cone hotter can help, as will a soak at the end of the firing.
Grog can be a problem, especially Maryland Refractorie's coarser grogs. I've seen a number of instances where there was a neat little pinhole above each bit of grog on the surface of the clay. Overall, this glaze always
seems happier on a smooth, low iron body.
Application matters a lot. If the glaze is applied too thinly, especially at cone six, it will tend to have problems. Because of the neph sy and lithium carb in this glaze, it REALLY needs to be flocculated. I use a little
muriatic acid- maybe a couple of tablespoons per five gallons of glaze (that's about 20 ml per 10,000 gram batch, for those of you in places with rational measuring systems). Epsom salts or calcium chloride also work well.
Without the flocculant, this glaze will settle out horribly and will be difficult to apply without drips.
There is some "bad" strontium going around (doesn't that sound like a warning at Woodstock?). The raw powder should be fine, powdery, and a bright white- a lot like a good whiting or quartz. If your supplier sends you
strontium carbonate that's tan and granular, send it back. It won't work well in matt glazes, and it won't work at all at low fire.
You might be tempted to lower the titanium dioxide, since that's often associated with pinholing, but I don't think it's the culprit here. It never hurts to try, though. Lowering it will change both the color and texture of
the glaze, but it may be a change you like. Do not, however, use rutile instead of Titanium. 5% rutile can definitely cause problems in this glaze.
You could also lower the maturing temperature a bit with some boron. Between .05 and .1 moles goes a long way to help it mature at cone 5-6. I've used good ol' gerstley for this (about 5%), but a frit should work well too.
Keep in mind that it will "blanderize" it just a bit, in terms of texture. You could also add a bit more lithium carb, but of course you will increase any negative traits that tend to accompany it. Some years ago, I had a
student lower this glaze to cone 3 by adding both gerstley borate and lithium carb. If memory serves (and my memory isn't serving me particularly well today), she added 10% gerstley borate and 3% (additional) lithium
carbonate and fired it to a full cone 3 in a gas kiln. She was using it on sculpture, so leaching wasn't an issue. You may want to have it tested it you use this version on pots.
Well, that's all I can get out of my fevered brain. If I think of anything else, I'll pass it along.
Pete Pinnell
PS Craig- thanks for the "heads up" on this.
Cindy Strnad on wed 14 nov 01
Wow!
Have I ever had tons of useful and helpful
responses to the Weathered Bronze Green question!
Thanks so much, everyone. I'm going to try several
things, and will let the list know what I find
out.
Basically, it sounds as if my grog-rich,
iron-rich, manganese-flecked body isn't the best
mate for this glaze. I'll try leaving out the grog
and coating my pieces with some EPK slurry (this
fits my body as a slip on greenware--lucky me),
Making some pieces in white clay, porcelain, and
trying the glaze on some ^9 pieces I've had
sitting around, awaiting proper clothing. I'm also
going to try altering the glaze chemistry as
David, Ron, John, and Pete (and others) have
suggested.
Thanks again,
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
cindy@earthen-vessels-pottery.com
http://www.earthen-vessels-pottery.com
Paul Taylor on fri 16 nov 01
Dear cindy
Its the dreaded titanium pinholes. Its a perennial discussion on this list
I have never seen a definitive answer . Years ago my titanium glaze started
to do it . I gave up and changed the range. now I have a small 3.3 cu ft
test kiln so if the problem happened again I would be able so solve it, but
I prefer the new range.
However if you do manage to find out why I would like to know, because I
would like to glaze the occasional pot in a titanium matt. Titanium reacts
well on top of colored slips it seems to drag the color out of the slip into
the glaze.
If you do cut down on the titanium as an experiment. you could try slow
cooling the kiln. By doing this you may be able to make up for the lack of
opacity by breeding your titanate crystals a bit bigger - but with out a
test kiln you have to be a brave soul to do such tests.
I do note that many titanium mats do lack silica The reason they do not
craze badly is a mystery to me. I wonder if the gaps between the crystals
give the glaze an illusion of more elasticity like there are no stress
cracks in cobbles only in concrete. the shrinkage is there but it does not
manifest as crazing. This of course just speculation on my behalf.
--
Regards from Paul Taylor
There is no such fury as self interest posing as moral principle.
http://www.anu.ie/westportpottery
> From: Cindy Strnad
> Reply-To: Ceramic Arts Discussion List
> Date: Sun, 11 Nov 2001 21:00:50 -0700
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: Weathered Bronze Green
>
> I am liking weathered bronze green more and more.
> Though I only use it outside and on decorative
> pieces, the pinholes are beginning to bug me. I
> get them on clean, soaked bisque, thick or thin
> glaze, slow cool, with a long soak at peak temp,
> with a short soak at peak temp . . . well, you get
> the picture. I'd like to start using it on pieces
> for sale if I can solve this problem without
> changing the appearance too much. Any suggestions?
>
> Weathered Bronze Green ^6
> Pete Pinnell
> =======================================
> LITHIUM CARBONATE... 1.00 0.91%
> STRONTIUM CARBONATE. 20.00 18.18%
> NEPHELINE SYENITE... 60.00 54.55%
> OM #4 BALL CLAY..... 10.00 9.09%
> FLINT............... 9.00 8.18%
> TITANIUM DIOXIDE.... 5.00 4.55%
> *Copper Carbonate.... 5.00 4.55%
> ========
> 110.00
>
> CaO 0.03* 0.57%
> Li2O 0.05* 0.42%
> MgO 0.00* 0.06%
> K2O 0.11* 3.09%
> Na2O 0.35* 6.63%
> SrO 0.46* 14.49%
> TiO2 0.22 5.29%
> Al2O3 0.56 17.50%
> SiO2 2.82 51.79%
> Fe2O3 0.00 0.16%
>
> Cost/kg 0.68
> Si:Al 5.02
> SiB:Al 5.02
> Expan 9.28
>
> Thanks,
>
> Cindy Strnad
> Earthen Vessels Pottery
> RR 1, Box 51
> Custer, SD 57730
> USA
> cindy@earthen-vessels-pottery.com
> http://www.earthen-vessels-pottery.com
Ababi on thu 27 dec 01
I think that adding materials to lower temperature out of the recipe
will change it.
This is the reason that I try to add flux from the list of flux I have
in the recipe
I made this test I will try to convert it to you:
PETE PINNELL BASE FOR ^ 6 1201deg.C. Cone 6
------------------------------------------------------------------------
----------------------------
Formula Weight% Recipe
------------------------------------------------------------------------
----------------------------
KNO 0.386 9.55% Feldspar Soda F7 14.00
CaO 0.086 1.93% Lithium Carbonate 1.00
MgO 0.044 0.70% BALL CLAY AK 27.00
Li2O 0.040 0.48% STRONTIUM CARBONATE 22.00
SrO 0.444 18.29% FRIT A 2120 p 24.00
Al2O3 0.445 18.04% SILICA 4.00
SiO2 2.119 50.69% Alumina Trihydrate 8.00
TiO2 0.010 0.32%
K2O 0.002 0.07%
Na2O 0.384 9.47%
Al:Si 4.764
Expan. 9.739
ST 376.261
-----------------
I did not write the colorants in the recipe but according to the
results I made the weathered green.
If you live in Israel, or in Italy- where they dig this feldspar and
make this frit it is fine.
Now I must add B2O3 as I will have to use frit 3110. (OR 4110)
PETE PINNELL BASE.3110 1201deg.C. Cone 6
------------------------------------------------------------------------
----------------------------
Formula Weight% Recipe
------------------------------------------------------------------------
----------------------------
KNO 0.390 10.16% Nepheline Syenite 29.00
CaO 0.100 2.18% Lithium Carbonate 1.00
MgO 0.027 0.41% BALL CLAY AK 15.00
Li2O 0.040 0.47% STRONTIUM CARBONATE 22.00
SrO 0.443 17.84% FRIT 3110 26.00
Al2O3 0.454 17.95% Alumina Trihydrate 7.00
B2O3 0.029 0.78%
SiO2 2.144 50.04%
TiO2 0.006 0.17%
K2O 0.061 2.24%
Na2O 0.329 7.92%
Al:Si 4.727
Expan. 9.700
ST 373.518
Results: Must be thick looks similar to the original. where it is thin
light green, not nice but not ugly the way it happens with the too thin
original weathered green!
I would not remove any of the titanium as it has a mottling effect, yet
I think I should use more copper perhaps instead of 5 copper carbonate
6 or even 7 which is pretty on the border of gray.
Or smaller amounts of copper oxide.
You can see that I mainly adjusted the level of the alumina to be matte
almost border of maturing. The glaze is similar to the original glaze
but should be tested again and better results.
Ababi Sharon
Kibbutz Shoval- Israel
Glaze addict
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910/
http://www.milkywayceramics.com/cgallery/asharon.htm
http://www.israelceramics.org/
---------- Original Message ----------
>Hi everyone,
>This is really a cone 9-10 glaze, and is at the very low end of its
>range at cone 6. In fact, without the copper it doesn't mature until
>about cone 7.
>Pete Pinnell
Jim and Marge Wade on mon 4 nov 02
I have a question regarding this glaze settling out so hard. When it's =
first mixed it's great - nice verdgris color - but after it's been =
around for a while it seems impossible to get it mixed thoroughly again. =
Even though it appears that I've put on a good coat, after firing it's =
more of a golden tan color at ^10 reduction (or thin black/tan in ^6 =
electric) with very little of the verdris green color it's known for. =
I've tried pouring off the liquid portion, drying and crumbling the =
settled out bottom, adding water and some suspender (2-4%), adding back =
the liquid portion then resieving it all several times. Still very =
little green at all. Any suggestions would be very welcome! It's a =
beautiful glaze I'd like to continue using.
Marge
| |
|
