The Kline's on sun 22 aug 99
To the Glaze Gurus,
I've been using Gibby's Wild Rose on the outside of casseroles and teapots,
and putting a clear liner glaze inside. But now I would like to glaze some
espresso cups inside and out with Wild Rose. Is there a problem with RIO
leaching? I read Tom Buck's posting about iron oxide last year, but would
appreciate some expansion on this.
I'm using the standard recipe:
lithium carbonate 9.50
bone ash 9.50
neph.syenite 55.66
EPK kaolin 15.84
RIO 9.50
fired to cone 6 oxidation.
As always, many thanks.
Marjory
Dave Finkelnburg on sun 22 aug 99
Question for all,
Just to really display my ignorance of this subject, if Marjory's glaze
does leach iron, aside from the possible deterioration of the glaze surface,
is the iron leaching a health problem? Thanks!
Dave Finkelnburg
-----Original Message-----
From: The Kline's
To: CLAYART@LSV.UKY.EDU
Date: Sunday, August 22, 1999 7:27 PM
Subject: Gibby's Wild Rose Tenmoku
----------------------------Original message----------------------------
To the Glaze Gurus,
I've been using Gibby's Wild Rose on the outside of casseroles and teapots,
and putting a clear liner glaze inside. But now I would like to glaze some
espresso cups inside and out with Wild Rose. Is there a problem with RIO
leaching? I read Tom Buck's posting about iron oxide last year, but would
appreciate some expansion on this.
I'm using the standard recipe:
lithium carbonate 9.50
bone ash 9.50
neph.syenite 55.66
EPK kaolin 15.84
RIO 9.50
fired to cone 6 oxidation.
As always, many thanks.
Marjory
Ron Roy on mon 23 aug 99
Iron is not a problem for most people - still - should we be supplying it?
The more serious problem with this glaze is the lithium - this is not a
glaze I would recommend to be in contact with food.
RR
>----------------------------Original message----------------------------
>To the Glaze Gurus,
>
>I've been using Gibby's Wild Rose on the outside of casseroles and teapots,
>and putting a clear liner glaze inside. But now I would like to glaze some
>espresso cups inside and out with Wild Rose. Is there a problem with RIO
>leaching? I read Tom Buck's posting about iron oxide last year, but would
>appreciate some expansion on this.
>
>I'm using the standard recipe:
>
>lithium carbonate 9.50
>bone ash 9.50
>neph.syenite 55.66
>EPK kaolin 15.84
>RIO 9.50
>
>fired to cone 6 oxidation.
>
>As always, many thanks.
>
>Marjory
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
John Hesselberth on sun 25 nov 01
on 11/25/01 6:04 PM, Lynn Korbel at sibylla5@YAHOO.COM wrote:
i am working with 3
> base glazes and~~gibby's wild rose tenmoku (wrt). and
> this is why i am writing--the wrt. have researched
> archives and not found any leads (that i recognize
> anyway) as to my last test result. having run out of
> bisque test bowls i used an old bisque-fired lid--rim
> waxed. dipped each side to different counts. fired it
> ^6 ox. the glaze shivered and flaked all around the
> lid onto the tile & some found its way between shelves
> to the lower level and fell onto another piece. when
> it shivered the kiln must of been cool enough as no
> damage occured to the other piece. so i think--need
> to see what i can do to stop the glaze flaking off.
> but this is what i cannot find any reference to: the
> interior of the lid glazed beautifully! my question
> is this: why? why is it so perfect under the lid
> while the top is a disaster? does this mean if i
> want to use this glaze i should cover the wrt piece
> with another--a sagger? please accept my apology if
> this is a dum question.
>
> warm regards,
> Lynn
Hi Lynn,
This is not a dumb question at all. Gibby's wild rose has some fundamental
problems. It was leach tested a couple years ago and you can see the
results on my web site (url below). It has a high level of lithium
carbonate as one of the ingredients. Lithium carbonate is partially soluble
in water and, hence, you can get dramatic variation in composition even over
one piece of pottery. I believe Ron Roy will tell you he has seen both
shivering and crazing on the same piece of pottery when the glaze has a high
level of lithium carbonate. Significant quantities of lithium should always
be sourced from spodumene which provides it in insoluble form. The other
problem with Gibby's is that it has a very low level of silica. This
guarantees it will not be a good stable glaze. It is definitely one to be
avoided on functional work.
Regards,
John
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.
Lynn Korbel on sun 25 nov 01
Dear Potters,
after 7 years i have at last reached the time for me
to begin mixing/creating glazes. i am working with 3
base glazes and~~gibby's wild rose tenmoku (wrt). and
this is why i am writing--the wrt. have researched
archives and not found any leads (that i recognize
anyway) as to my last test result. having run out of
bisque test bowls i used an old bisque-fired lid--rim
waxed. dipped each side to different counts. fired it
^6 ox. the glaze shivered and flaked all around the
lid onto the tile & some found its way between shelves
to the lower level and fell onto another piece. when
it shivered the kiln must of been cool enough as no
damage occured to the other piece. so i think--need
to see what i can do to stop the glaze flaking off.
but this is what i cannot find any reference to: the
interior of the lid glazed beautifully! my question
is this: why? why is it so perfect under the lid
while the top is a disaster? does this mean if i
want to use this glaze i should cover the wrt piece
with another--a sagger? please accept my apology if
this is a dum question.
warm regards,
Lynn
__________________________________________________
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Paul Lewing on sun 25 nov 01
on 11/25/01 3:04 PM, Lynn Korbel at sibylla5@YAHOO.COM wrote:
> i used an old bisque-fired lid--rim
> waxed. dipped each side to different counts.
Lynn, do you mean that you glazed the right half of the lid thicker (or
thinner) than the left half, or do you mean that you glazed the inside
thicker (or thinner) than the outside? It's possible that shape of the lid
is what's causing the glaze to flake off the inside but not the outside. If
you think about glaze fit as being analogous to clothes fitting, you can
easily visualize the difference between how it would fit inside a depression
as opposed to how it would fit over a hump.
fired it
> ^6 ox. the glaze shivered and flaked all around the
> lid onto the tile & some found its way between shelves
> to the lower level and fell onto another piece. when
> it shivered the kiln must of been cool enough as no
> damage occured to the other piece. so i think--need
> to see what i can do to stop the glaze flaking off.
> but this is what i cannot find any reference to: the
> interior of the lid glazed beautifully! my question
> is this: why? why is it so perfect under the lid
> while the top is a disaster? does this mean if i
> want to use this glaze i should cover the wrt piece
> with another--a sagger?
I don't think that would have much effect, except that firing inside a
saggar would mean that it would cool more slowly, which might affect the
shivering, although I think it would just delay it.
The real problem, and the solution, is chemical. The coefficient of
expansion of this glaze is too low for your clay body and firing schedule.
This is a very weird glaze. It has a lot of lithium in it, if I remember
right, in the form of lithium carbonate, which can cause problems. Look in
the archives for more information on that. I'd try cutting down the lithium
a little at a time, and seeing how much you could take out and still retain
the look you like.
Paul Lewing, Seattle
Cindy Strnad on sun 25 nov 01
Dear Lynn,
Gibby's Wild Rose (I include my recipe here, in
case anyone wants to know, or in case yours is
different) is very high in lithium. That's why it
can craze in one part of the pot and shiver in
another part. I suspect you had the glaze thickest
where it shivered. Most irritating, but it is a
pretty glaze. Still you don't want shards in your
coffee. Aside from the high lithium content (which
some may see as a benefit ), this is the
reason I've designated it as "not food safe". I
haven't had it tested or anything.
It's low in silica and even lower in alumina.
Obviously not designed for its tough character.
No, it's the coppery flickers we love.
Gibby's Wild Rose Tenmoku ^6
Not food safe.
=============================================
LITHIUM CARBONATE... 10.00 10.00%
BONE ASH............ 10.00 10.00%
NEPHELINE SYENITE... 55.00 55.00%
EPK KAOLIN.......... 15.00 15.00%
RIO................. 10.00 10.00%
========
100.00
CaO 0.28* 6.15%
Li2O 0.38* 4.44%
MgO 0.00* 0.03%
K2O 0.08* 2.94%
Na2O 0.26* 6.39%
TiO2 0.00 0.06%
Al2O3 0.51 20.32%
P2O5 0.09 5.03%
SiO2 1.85 43.79%
Fe2O3 0.17 10.86%
Cost/kg 2.57
Si:Al 3.66
SiB:Al 3.66
Expan 8.84
Try covering it with a thin layer of this glaze:
Dale Huffman's Saturated Iron Oxide
^6 Oxidation
=================================================
GERSTLEY BORATE..... 29.00 29.00%
FLINT............... 20.00 20.00%
CUSTER FELDSPAR..... 14.00 14.00%
TALC................ 9.00 9.00%
EPK KAOLIN.......... 3.00 3.00%
*Red Iron Oxide...... 25.00 25.00%
========
100.00
CaO 0.45* 10.63%
MgO 0.37* 6.22%
K2O 0.06* 2.21%
Na2O 0.12* 3.06%
TiO2 0.00 0.02%
Al2O3 0.14 5.95%
B2O3 0.44 12.89%
P2O5 0.00 0.01%
SiO2 2.35 58.83%
Fe2O3 0.00 0.18%
Cost/kg 1.38
Si:Al 16.78
SiB:Al 19.96
Expan 6.51
I think you will love the coppery, glittery
results. (I haven't had this combination tested,
either, but possibly, possibly, the overcoat of
SIO may stabilize the Wild Rose a bit.
Unfortunately, the pretty glitter only really
shows up in bright sunlight, which is in short
supply in most retail shops. At any rate, before
you decided to sell the stuff, you really should
a) test the glaze yourself for crazing/shivering,
and b) test the glaze for lithium release.
Best wishes,
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 mon 26 nov 01
Dear lynn.
You must load a recipe when you ask for help.
About this glaze:
Gibby's Khaki (also called Wild Rose Tenmoku), Ox., cone 6
Lithium Carbonate... 10.50 9.50%
Bone Ash............ 10.50 9.50%
Nepheline Syenite... 61.50 55.66%
Tile 6 Kaolin....... 17.50 15.84%
Red Iron Oxide...... 10.50 9.50%
========
110.50
CaO 0.27* 5.84%
Li2O 0.37* 4.21%
MgO 0.00* 0.03%
K2O 0.08* 2.98%
Na2O 0.27* 6.45%
TiO2 0.00 0.07%
Al2O3 0.53 20.79%
P2O5 0.09 4.78%
SiO2 1.94 44.55%
Fe2O3 0.17 10.30%
Text1 15.82
Si:Al 3.64
SiB:Al 3.64
Expan 8.80
I will be carful from saying things I do not know exactly, but:
This glaze has a lot of lithium. Means low expansion which tend to
flake off while cooling. Do you use the same claybody you have
used before? You should try it on several claybodies. My experience
with high lithium glaze like this that from some claybodies it is
flucing of will on others it is fine: Acording to the expansion of
these claybodies.
Dunting! this is the word.
Or use less lithium
but will it be the same glaze?
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 ----------
>Dear Potters,
>after 7 years i have at last reached the time for me
>to begin mixing/creating glazes. i am working with 3
>base glazes and~~gibby's wild rose tenmoku (wrt). and
>this is why i am writing--the wrt. have researched
>archives and not found any leads (that i recognize
>anyway) as to my last test result. having run out of
>bisque test bowls i used an old bisque-fired lid--rim
>waxed. dipped each side to different counts. fired it
>^6 ox. the glaze shivered and flaked all around the
>lid onto the tile & some found its way between shelves
>to the lower level and fell onto another piece. when
>it shivered the kiln must of been cool enough as no
>damage occured to the other piece. so i think--need
>to see what i can do to stop the glaze flaking off.
>but this is what i cannot find any reference to: the
>interior of the lid glazed beautifully! my question
>is this: why? why is it so perfect under the lid
>while the top is a disaster? does this mean if i
>want to use this glaze i should cover the wrt piece
>with another--a sagger? please accept my apology if
>this is a dum question.
>warm regards,
>Lynn
>__________________________________________________
>Do You Yahoo!?
>Yahoo! GeoCities - quick and easy web site hosting, just $8.95/month.
>http://geocities.yahoo.com/ps/info1
>_______________________________________________________________________
_
>______
>Send postings to clayart@lsv.ceramics.org
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>Moderator of the list is Mel Jacobson who may be reached at
>melpots@pclink.com.
Paul Lewing on mon 26 nov 01
on 11/26/01 7:49 AM, Lynn Korbel at sibylla5@YAHOO.COM wrote:
>> Lynn, do you mean that you glazed the right half of
>> the lid thicker (or
>> thinner) than the left half, or do you mean that you
>> glazed the inside
>> thicker (or thinner) than the outside?
> Dear Paul,
> i did glaze the right half thinner than the
> left--including the top and the bottom.
Well, I'd say that means it's the shape of the surface that's making it
shiver off one face and not the other. But, as you've probably gathered by
now from all the posts on this glaze, it's not a stable glaze. In fact, I'd
bet that if it flaked off one face that fast, it's only a matter of time
before it flakes off the other face, too.
Paul Lewing, Seattle
Alisa og Claus Clausen on mon 26 nov 01
Dear Lynn,
I was also very much in like with the color and sparkle of Gibby's Wild Rose.
But I left in the glaze recipe book as tested a few times and no further use.
Like Cindy, I have another recipe that has been on Clayart recently again,
that also gives a
sparkling iron surface. Also nice under Rutile or white glosses.
Red Gold
cone 6 ox.
2 Barium carb.
7 Gerstely Borate
11 Lithium Carb.
3 Magnesium
14 Whiting
24 Neph. Sye
39 Flint
ADD
RIO 7
Rutile 6
Zircopax 6
Lynn Korbel on mon 26 nov 01
--- Paul Lewing wrote:
> on 11/25/01 3:04 PM, >
> > i used an old bisque-fired lid--rim
> > waxed. dipped each side to different counts.
> Lynn, do you mean that you glazed the right half of
> the lid thicker (or
> thinner) than the left half, or do you mean that you
> glazed the inside
> thicker (or thinner) than the outside?
Dear Paul,
i did glaze the right half thinner than the
left--including the top and the bottom. did not
overlap the glazing so there is a distinct clay-line
between the two. looks like i have a "monolyth" of a
problem--to persue or not to persue this glaze. :-)
It's
> possible that shape of the lid
> is what's causing the glaze to flake off the inside
> but not the outside. If
> you think about glaze fit as being analogous to
> clothes fitting, you can
> easily visualize the difference between how it would
> fit inside a depression
> as opposed to how it would fit over a hump.
>
> fired it
> > ^6 ox. the glaze shivered and flaked all around
> the
> > lid onto the tile & some found its way between
> shelves
> > to the lower level and fell onto another piece.
> when
> > it shivered the kiln must of been cool enough as
> no
> > damage occured to the other piece. so i
> think--need
> > to see what i can do to stop the glaze flaking
> off.
> > but this is what i cannot find any reference to:
> the
> > interior of the lid glazed beautifully! my
> question
> > is this: why? why is it so perfect under the lid
> > while the top is a disaster? does this mean if i
> > want to use this glaze i should cover the wrt
> piece
> > with another--a sagger?
> I don't think that would have much effect, except
> that firing inside a
> saggar would mean that it would cool more slowly,
> which might affect the
> shivering, although I think it would just delay it.
> The real problem, and the solution, is chemical.
> The coefficient of
> expansion of this glaze is too low for your clay
> body and firing schedule.
> This is a very weird glaze. It has a lot of lithium
> in it, if I remember
> right, in the form of lithium carbonate, which can
> cause problems. Look in
> the archives for more information on that. I'd try
> cutting down the lithium
> a little at a time, and seeing how much you could
> take out and still retain
> the look you like.
> 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.
__________________________________________________
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Lynn Korbel on mon 26 nov 01
Dear Cindy, et al;
thank you very much for your gibby's wrt recipe and
the Dale Huffman's Saturated Iron Oxide. my wrt
recipe is different than yours:
Gibby's Wild Rose Tenmoku ^6 ox
Lithium Carbonate 10.5
Bone Ash 10.5
Nepheline Syenite 61.5
EPK 17.5
Red Iron Oxide 10.5
copied it from clayart--don't remember when. then 3
days ago found this next one in the archives:
Gibby's Wild Rose Tenmoku ^6 ox
Lithium Carbonate 9.5
Bone Ash 9.5
Nepheline Syenite 55.7
EPK 15.8
Red Iron Oxide 9.5
i will give your recipe and the 2d one a try. i am
not willing to change my clay--i know this
inflexibility is not good but there you go. i use
standard's 112 brown clay. if i ever get this glaze
to stay on the pot i will have it tested, however i
was not planning to use it on ware intended for food.
except maybe the outside of a tea-pot...yes--testing
would be best. thank you again Cindy, and thank you
to everyone for your replies. my education continues,
for i really thought it might be more of a cooling
thing than chemical (the glaze inside the lid is still
holding on!) or is it both? good grief.
Lynn in foggy mississippi
--- Cindy Strnad wrote:
> Dear Lynn,
>
> Gibby's Wild Rose (I include my recipe here, in
> case anyone wants to know, or in case yours is
> different) is very high in lithium. That's why it
> can craze in one part of the pot and shiver in
> another part. I suspect you had the glaze thickest
> where it shivered. Most irritating, but it is a
> pretty glaze. Still you don't want shards in your
> coffee. Aside from the high lithium content (which
> some may see as a benefit ), this is the
> reason I've designated it as "not food safe". I
> haven't had it tested or anything.
>
> It's low in silica and even lower in alumina.
> Obviously not designed for its tough character.
> No, it's the coppery flickers we love.
>
> Gibby's Wild Rose Tenmoku ^6
> Not food safe.
> =============================================
> LITHIUM CARBONATE... 10.00 10.00%
> BONE ASH............ 10.00 10.00%
> NEPHELINE SYENITE... 55.00 55.00%
> EPK KAOLIN.......... 15.00 15.00%
> RIO................. 10.00 10.00%
> ========
> 100.00
>
> CaO 0.28* 6.15%
> Li2O 0.38* 4.44%
> MgO 0.00* 0.03%
> K2O 0.08* 2.94%
> Na2O 0.26* 6.39%
> TiO2 0.00 0.06%
> Al2O3 0.51 20.32%
> P2O5 0.09 5.03%
> SiO2 1.85 43.79%
> Fe2O3 0.17 10.86%
>
> Cost/kg 2.57
> Si:Al 3.66
> SiB:Al 3.66
> Expan 8.84
>
> Try covering it with a thin layer of this glaze:
>
> Dale Huffman's Saturated Iron Oxide
> ^6 Oxidation
> =================================================
> GERSTLEY BORATE..... 29.00 29.00%
> FLINT............... 20.00 20.00%
> CUSTER FELDSPAR..... 14.00 14.00%
> TALC................ 9.00 9.00%
> EPK KAOLIN.......... 3.00 3.00%
> *Red Iron Oxide...... 25.00 25.00%
> ========
> 100.00
>
> CaO 0.45* 10.63%
> MgO 0.37* 6.22%
> K2O 0.06* 2.21%
> Na2O 0.12* 3.06%
> TiO2 0.00 0.02%
> Al2O3 0.14 5.95%
> B2O3 0.44 12.89%
> P2O5 0.00 0.01%
> SiO2 2.35 58.83%
> Fe2O3 0.00 0.18%
>
> Cost/kg 1.38
> Si:Al 16.78
> SiB:Al 19.96
> Expan 6.51
>
> I think you will love the coppery, glittery
> results. (I haven't had this combination tested,
> either, but possibly, possibly, the overcoat of
> SIO may stabilize the Wild Rose a bit.
> Unfortunately, the pretty glitter only really
> shows up in bright sunlight, which is in short
> supply in most retail shops. At any rate, before
> you decided to sell the stuff, you really should
> a) test the glaze yourself for crazing/shivering,
> and b) test the glaze for lithium release.
>
> Best wishes,
>
> Cindy Strnad
> Earthen Vessels Pottery
> RR 1, Box 51
> Custer, SD 57730
> USA
> cindy@earthen-vessels-pottery.com
> http://www.earthen-vessels-pottery.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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Craig Martell on mon 26 nov 01
Hi folks:
I've looked at this glaze several times via Clayart. It's way out of whack
and is potentially very troublesome. Sure, it looks good and would be great
if it stayed on your pots.
One of the real odd things about gibby's is that is has a very high
calculated expansion, around 8.84 X10-6 but it still shivers. My feeling
is that it does shiver because there's a lot of lithium and not enough
silica to engage the lithium, which has a very high Coefficient of
Diffusion, meaning that it's very mobile and can penetrate the glaze matrix
and the clay glaze interface. Shivering occurs in the interface and the
glaze fractures and pops off the pot while the glass matrix itself is still
high expansion and crazes. The crazing would depend on the thickness of
the glaze. If it were thinner, most of the lithium would penetrate into
the interface. This is hypothetical thinking though.
Gibby's also has one of the lowest silica/alumina ratios that I've seen in
a glaze. It's lower that most claybodies.
I'd avoid this glaze. I know that some have gotten it to work on their
clays but it's a real outsider.
regards, Craig Martell in Oregon
Cindy Strnad on mon 26 nov 01
Dear Lynn,
If you cool the glaze more slowly, it will shiver
more slowly, but it will eventually shiver if it
doesn't fit the pot. The pieces on which I also
applied the SIO have not shivered yet, and that's
been, maybe, a year or more. It seems to enhance
the appearance of the Wild Rose as well. There's
no need to change your clay, though. I don't think
this glaze, by itself, will fit any clay.
Good Luck,
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
cindy@earthen-vessels-pottery.com
http://www.earthen-vessels-pottery.com
tomsawyer on mon 26 nov 01
Lynn,
I've been using Gibby's Wild Rose for about the last 6 months on
non-functional ware [mainly flower pots and vases] and love it. I've fired
it on about 20-30 pots spread over about 10 firings and have never had even
the slightest problem. What others have said about the lithium and silica is
relevant but you might also reflect about the glaze application; might it
have been too thick on the top?
Tom Sawyer
tsawyer@cfl.rr.com
iandol on tue 27 nov 01
Dear John Hesselberth,
You say spodumene which provides it in insoluble form. >
Although it contains a lower proportion of Lithium to Silica/Alumina, =
Petalite is also an excellent source which should not be overlooked when =
seeking an alternative compound which contains the element Lithium.
Best regards,
Ivor Lewis, Redhill, South Australia
John Hesselberth on wed 28 nov 01
on 11/27/01 12:42 AM, iandol at iandol@TELL.NET.AU wrote:
> Although it contains a lower proportion of Lithium to Silica/Alumina, Petalite
> is also an excellent source which should not be overlooked when seeking an
> alternative compound which contains the element Lithium.
You are right Ivor, but Petalite is often difficult to find in North
America.
Regards,
John
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.
Ron Roy on thu 29 nov 01
OK - I can't do it - keep quite on this subject - I tried as hard as I can
but my hands are typing without me.
Just hang in for a bit - there is a smile at the end.
Because so many (I could say 99% I suppose until recently) potters had such
a profound lack of information about glaze technology - I have to include
myself in this for the first 30 years of pottery - we used simple
solutions.
An example: We want a lowfire glaze to melt more - we know Lithium oxide is
a low fire flux similar to Sodium and Potassium - and - unlike those it is
available in carbonate form. So adding it to the glaze will make it melt
more - and even work well enough in some cases to do the job.
OK - lets extrapolate to other temperatures - we can use it to melt cone 6
and even cone 10 glazes. Excellent alkaline flux - and it has a lower
expansion than both sodium and potassium so it will help with any crazing
problem.
OK - most of them didn't know the expansion stuff - so already there were
potential fit problems lurking.
Add to that - of all the carbonates we use Lithium Carb is the most
soluble. So glazes get deflocculated - OK we can deal with that - but - the
real problem - if you have say more than 2% lthium Carb in a glaze - enough
of that soluble lithium can move around in the ware during drying. It can
not only change the expansion of the glaze but can effect the clay.
Picture this - The soluble lithium affects the body because it is now
deposited in different areas. So now - instead of having one clay and one
glaze you have the clay affected in such a way as to have many different
expansion rates.
Unpredictable - you betcha - can you tell when it's going to happen - no
you can't - do you want to try and market ware under those conditions - no
you don't.
I have a standard answer for anyone wanting to use lithium in a glaze -
keep it below 2% - or better still use Spodumene or Petalite or a lithium
bearing frit.
Trying to solve clay and glaze problems without understanding is bound to
get you into trouble sooner or later - and as most production potters will
tell you - usually just before some sort of deadline. Don't assume all
those glazes we find everywhere were made by people that understood what
they were doing - the great majority did not have a clue - it worked for
them - sometimes.
The real miracle is that so much of the ware we make survives at all. Would
it pass the testing that factory produced ware must to keep selling - some
of it would - but mostly by accident.
We now have excellent tools for helping design good well fitting glazes and
clay that will do what it should - the problem now is to build the skills
needed and convince those in charge of educating us that the very least
they can do is point to those tools if not actually understand them.
Maybe someone could revise the young and old bull story to cover the
situation. All I can say is - I'm over the hill and there is an awful lot
of work to be done.
RR
>Although it contains a lower proportion of Lithium to Silica/Alumina,
>Petalite is also an excellent source which should not be overlooked when
>seeking an alternative compound which contains the element Lithium.
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
Terry Hunt on tue 2 jul 02
----- Original Message -----
From: "Paul Lewing"
To:
Sent: Sunday, November 25, 2001 6:50 PM
Subject: Re: gibby's wild rose tenmoku
> on 11/25/01 3:04 PM, Lynn Korbel at sibylla5@YAHOO.COM wrote:
>
> > i used an old bisque-fired lid--rim
> > waxed. dipped each side to different counts.
> Lynn, do you mean that you glazed the right half of the lid thicker (or
> thinner) than the left half, or do you mean that you glazed the inside
> thicker (or thinner) than the outside? It's possible that shape of the
lid
> is what's causing the glaze to flake off the inside but not the outside.
If
> you think about glaze fit as being analogous to clothes fitting, you can
> easily visualize the difference between how it would fit inside a
depression
> as opposed to how it would fit over a hump.
>
> fired it
> > ^6 ox. the glaze shivered and flaked all around the
> > lid onto the tile & some found its way between shelves
> > to the lower level and fell onto another piece. when
> > it shivered the kiln must of been cool enough as no
> > damage occured to the other piece. so i think--need
> > to see what i can do to stop the glaze flaking off.
> > but this is what i cannot find any reference to: the
> > interior of the lid glazed beautifully! my question
> > is this: why? why is it so perfect under the lid
> > while the top is a disaster? does this mean if i
> > want to use this glaze i should cover the wrt piece
> > with another--a sagger?
> I don't think that would have much effect, except that firing inside a
> saggar would mean that it would cool more slowly, which might affect the
> shivering, although I think it would just delay it.
> The real problem, and the solution, is chemical. The coefficient of
> expansion of this glaze is too low for your clay body and firing schedule.
> This is a very weird glaze. It has a lot of lithium in it, if I remember
> right, in the form of lithium carbonate, which can cause problems. Look
in
> the archives for more information on that. I'd try cutting down the
lithium
> a little at a time, and seeing how much you could take out and still
retain
> the look you like.
> Paul Lewing, Seattle
>
>
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Ron Roy on wed 3 jul 02
Hi Lunn,
I have warned about high Lithium carb in clazes before on this list - I
need to look at the recipe - perhaps it's just a matter of subbing in more
KNaO to lower the lithium content and raise the expansion.
Lithium barb is somewhat soluble and if the lid was dried upright the
migrating salts may be to blame. I have seen glazes with more than 2%
Lithium carb craze and siver at the same time.
RR
>> > i used an old bisque-fired lid--rim
>> > waxed. dipped each side to different counts.
>> > ^6 ox. the glaze shivered and flaked all around the
>> > lid onto the tile & some found its way between shelves
>> > to the lower level and fell onto another piece. when
>> > it shivered the kiln must of been cool enough as no
>> > damage occured to the other piece. so i think--need
>> > to see what i can do to stop the glaze flaking off.
>> > but this is what i cannot find any reference to: the
>> > interior of the lid glazed beautifully! my question
>> > is this: why? why is it so perfect under the lid
>> > while the top is a disaster? does this mean if i
>> > want to use this glaze i should cover the wrt piece
>> > with another--a sagger?
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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