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mysterious bubbles, satin with copper carbonate

updated wed 24 sep 08

 

Maid O'Mud on wed 27 aug 08


Try Pg 97 (glossy clear liner) with 2-3% copper carb.
I've been using it for over a year with great results.

BTW, what's your firing schedule? That might be a factor
with your bubbling.

Sam Cuttell
Maid O'Mud Pottery
RR 1
Melbourne, Ontario
N0L 1T0
CANADA

"First, the clay told me what to do.
Then, I told the clay what to do.
Now, we co-operate."
sam 1994

http://www.ody.ca/~scuttell/
scuttell@ody.ca

-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of The Fuzzy Chef

Folks,

I'm firing in Cone 6 oxidation these days, and have made heavy use of
some of the glazes from Mastering Cone 6 Glazes. However, I seem to be
getting a odd reaction to copper in one glaze.

I've been using Glossy Base #1 (a Custer Feldspar & Ferro 3195 base)
with Cobalt for a nice deep blue, and it gives me a perfect transparent
gloss. However, when I add 2% copper carbonate to GB #1 to make a
celedon-like light green, the glaze develops a satin texture, and
bubbles where it pools.

Out of curiousity, I tried Glossy Base #2 from MC6G, and had the same issue.

Anyone seen anything like this? The addition of copper carbonate
causing bubbles? Or should I be looking somewhere else?

--Josh

The Fuzzy Chef on wed 27 aug 08


Sam,

> Try Pg 97 (glossy clear liner) with 2-3% copper carb.
> I've been using it for over a year with great results.

Thanks, will test. Too bad I mixed 5 gallons of the bad green.

> BTW, what's your firing schedule? That might be a factor
> with your bubbling.

Hmmm, don't think so. I've tried a couple different schedules, but the
telling point is that this glaze was on the same shelf with GB#1 with 2%
cobalt carbonate, and that came out beautifully and very glassy. In one
case, on the same piece. Also, my previous firing with GB#2 was longer
(12 hours) and came out the same.

These are both from the same firing, which did a perfect 8-hour cone 6
with a 15-minute hold:

Royal Blue:
http://fuzzychef.smugmug.com/photos/360515783_EYji9-O.jpg

Celedon Green:
http://fuzzychef.smugmug.com/photos/360516314_H4Awe-O.jpg

Those two were on the same shelf, made with batches I mixed the same
day. Yet you can see the "satin" texturing on the green.


--Josh

The Fuzzy Chef on wed 27 aug 08


Folks,

I'm firing in Cone 6 oxidation these days, and have made heavy use of
some of the glazes from Mastering Cone 6 Glazes. However, I seem to be
getting a odd reaction to copper in one glaze.

I've been using Glossy Base #1 (a Custer Feldspar & Ferro 3195 base)
with Cobalt for a nice deep blue, and it gives me a perfect transparent
gloss. However, when I add 2% copper carbonate to GB #1 to make a
celedon-like light green, the glaze develops a satin texture, and
bubbles where it pools.

Out of curiousity, I tried Glossy Base #2 from MC6G, and had the same issue.

Anyone seen anything like this? The addition of copper carbonate
causing bubbles? Or should I be looking somewhere else?

--Josh

Steve Slatin on thu 28 aug 08


Fuzzy --

This may at first sound silly,
but I have six green glazes,
and the highest concentration of
Copper Carb I use is 1.4%. Maybe
you can blend down the copper
carb with colorant-free base
and reduce the amount of carbonate
(and bubbling) in the glaze.

The other possiblity is that
the big batch of the base is not
correctly mixed, and your problem has
no relationship to the colorant.
Slightly too much alumina, or
insufficient frit might give
the result you got also.



Good luck -- Steve Slatin




--- On Wed, 8/27/08, The Fuzzy Chef wrote:

> Sam,
>
> > Try Pg 97 (glossy clear liner) with 2-3% copper carb.
> > I've been using it for over a year with great
> results.
>
> Thanks, will test. Too bad I mixed 5 gallons of the bad
> green.
>
> > BTW, what's your firing schedule? That might be a
> factor
> > with your bubbling.
>
> Hmmm, don't think so. I've tried a couple
> different schedules, but the
> telling point is that this glaze was on the same shelf with
> GB#1 with 2%
> cobalt carbonate, and that came out beautifully and very
> glassy. In one
> case, on the same piece. Also, my previous firing with
> GB#2 was longer
> (12 hours) and came out the same.
>
> These are both from the same firing, which did a perfect
> 8-hour cone 6
> with a 15-minute hold:
>
> Royal Blue:
> http://fuzzychef.smugmug.com/photos/360515783_EYji9-O.jpg
>
> Celedon Green:
> http://fuzzychef.smugmug.com/photos/360516314_H4Awe-O.jpg
>
> Those two were on the same shelf, made with batches I mixed
> the same
> day. Yet you can see the "satin" texturing on
> the green.
>
>
> --Josh

Neon-Cat on fri 29 aug 08


Ivor wrote:
"The contrast between the sample coloured with Cobalt oxide and that
coloured with Copper Carbonate reminded me that I have a list on the desk
relating to the Transitional Metal oxides and their behaviour
towards silicate melts. Cobalt oxide is soluble in silicate melts, forming a
solution colour. It also reacts to form Cobalt Orthosilicate. I can find no
record of Copper oxide forming an Orthosilicate. The Phase diagram, Cu2O.
SiO2, Fig 164 in the ACerS book (1979) implies that the two liquids are not
miscible and do not react with each other."

Ivor, I gotta ask if you're OK. I hope so. The question Josh asked concerned
copper carbonate and possible bubbling, not copper (I) oxide (cuprous oxide,
Cu2O), the red version of the oxide although, as we shall see, we can get to
that from copper carbonate. I bring this up only to bring your attention
back to the carbonate chemistry we covered a few posts back. I also want to
also remind you about the basic, fundamental copper chemistry we covered in
the recent copper red threads. You could have skipped fretting about cuprous
oxide and silica getting together, phase diagrams, orthosilicates, melting
temperatures (Josh is firing at Cone 6, 1222 C/2232 F, in an oxidation
atmosphere) and all the other too fancy stuff because copper carbonate
copper decomposes when heated in our kilns:

CuCO3 ---> CuO + CO2 (at 500 C)

To answer Josh's question, yes, all carbonates will bubble as they release
carbon dioxide when heated. Many of our glazes "heal" during their time in
the kiln but once in awhile we may see pinholes or blisters in glazes as the
result of the off-gasing of carbon dioxide. Josh could lengthen his firing
schedule slightly and see if that helps or switch to copper oxide for his
glaze color. Others have made good suggestions in this direction.

Now, once decomposed, Josh's copper carbonate formed cupric oxide (CuO), the
black stuff, in his kiln. His choice of glaze ingredients has set up the
normal sequential reduction process where CuCO3 and CuO are reduced to
copper. Then the copper can and does form all kinds of compounds with silica
through Cu-O-Si bonds or through exchange, substitution, interstitial
positioning, weak hydrogen bonding, or Van der Waal's forces. Ionic and
covalent bonds being but conceptual ideas only, please remember that in this
day and age bonds are thought of as having a percent ionic or covalent
character and arrange themselves accordingly, some compounds or minerals
more comfortably and securely than others. There are a number of mineral
examples of copper silicates (see below).

I might also remind everyone that chemical reactions are not perfect. In our
complicated Cu-CuCO3-CuO-Cu2O system that Josh presented, within different
atmospheres and at different temperatures, not all reactions will go to
completion and many are reversible. It should also be remembered that silica
can take crystalline (structured in regular patterns) or non-crystalline
forms (amorphous, e.g. opal and silica glasses). [Silica also has hydrous
phases (SiO2.nH2O) as well.] Thus, we may be seeing the results of a glaze
where only Cu is involved, or we may have a mixed system where the oxide
species are also present. In Josh's oxidation atmosphere cuprous oxide
(Cu2O) is but a transient intermediate as cupric oxide (CuO) reduces to
copper. Copper and its compounds, in this case CuO and Cu2O, may, of course,
be present as compounds of silica or merely find themselves entrapped within
the resultant glassy glaze. Ivor, if you worry about whether silica and Cu2O
are miscible (perhaps you should check the definition of miscible) and do
not react with each other you are worrying needlessly, especially in this
example posted by Josh. In cases where reduction or a mixed atmosphere is
employed, when the firing is done and the glaze cools and solidifies, any
unreacted Cu2O (as outlined by the equations below) will precipitate out
(usually to the surface) or remain entrapped within its host glaze. Where
else is it going to go, Ivor? That Cu2O does not form silica compounds just
isn't germane. That's why in previous posts I referred to the copper and
silica as forming "copper colloidal particles" - a type of mix where the
glaze serves as the dispersion medium for the copper in whatever form we
find it. Kinda like dropping a cucumber into white rum - the cucumber
doesn't dissolve or react with the rum, it just lightly flavors this "cool
refreshing summer time drink" as one of my old buds use to like to say. The
cucumber floats and bounces around within the more prominent rum liquid. So,
liken the cuprous oxide (Cu2O) to a cucumber in rum. Unlike the cucumber
that seems to have little effect on whether someone finds the drink easy to
imbibe and goes on to get blitzed or not, within a glaze any unreacted Cu2O
acts as a silica network breaker and has a strong effect on lowering the
viscosity of the molten glaze so that it will flow and run more when cuprous
oxide (Cu2O) is present. In this respect it is better than FeO or MnO on a
molar basis. And whatever form the copper takes, with or without chemically
combining with silica, the millions of twinkling electrons in the copper and
any other reactive atoms are responsible for our glaze colors as they are
excited and respond to light.

Anyway, the two applicable copper reactions (A & B below) for CuO ? Cu2O ?
Cu (at 250 C and higher) go like this:

A) 4CuO --> (heat, 1000 C) 2Cu2O + O2
We know that red cuprous oxide is unstable (particularly below 375 C) so it
does not linger around. However, in reduction atmospheres the Cu2O remains
stable without further reduction with continued exposure to CO.

B) Cu2O --> (heat) CuO + Cu

Other important copper equations:

CuO + C --> Cu + CO
2CuO + C ? 2 Cu + CO2
(heat with carbon, CO, or hydrocarbons present)

CuO + Cu --> Cu2O
(heat with a mix of cupric oxide and copper powder)

CuO + H2 ? Cu + H2O
(heat with H2)

Cu2O + 1/2O2 --> 2CuO
cuprous oxide heated and oxidized in air

Some copper silicate minerals:

Abswurmbachite
CuMn6O8(SiO4)

Ajoite
(K,Na)Cu7[(OH)6|AlSi9O24] 3H2O

Apachite
Cu9Si10O29.11H2O

Ashburtonite
Pb4Cu4[(OH)3|Cl|(HCO3)4|Si4O12] H2O

Chrysocolla (hydrated copper silicate)
CuSiO3 - nH2O

Creaseyite (Orthorhombic)
Cu2Pb2(Fe, AL)2Si5O17.6H2O

Cuprorivaite
CaCu[Si4 O10]

Cuprosklodowskite
Cu(UO2)2[HSiO4]2 6H2O

Dioptase (copper acid silicate)
CuSiO3H2O
(also reported as CuSiO2(OH)2)

Dixenite
CuMn14Fe[(OH)6|(AsO3)5|AsO4|(SiO4)2]

Effenbergerite
BaCu[Si4O10]

Gilalite
Cu5Si6O177H2O

IMA2007-043
Cu[Ti4O2(OH)2(SiO4)3]7H2O

Iranite
Pb10Cu[(F,OH)2|(CrO4)6|(SiO4)2]

Luddenite
Cu2Pb2Si5O14.4H2O

Macquartite
Pb3Cu(CrO4)(SiO3)(OH)4.2H2O

Papagoite
CaCu[H3AlSi2O9]

Shattuckite (Copper Silicate Hydroxide)
Chemistry: Cu5(SiO3)4(OH)2

Wesselsite
SrCu[Si4O10]


I hope copper chemistry is now a little more understandable to everyone. If
I were still a drinking woman I'd take a stiff belt of that refreshing
summer time drink right about now and toast my old bud. Typing is just not
my thing but sometimes there is no easy way to make chemistry simple without
spending a few words.

Marian
Neon-Cat Ceramics

Ivor and Olive Lewis on fri 29 aug 08


Dear Josh,
The contrast between the sample coloured with Cobalt oxide and that
coloured with Copper Carbonate reminded me that I have a list on the
desk relating to the Transitional Metal oxides and their behaviour
towards silicate melts.
Cobalt oxide is soluble in silicate melts, forming a solution colour.
It also reacts to form Cobalt Orthosilicate.
I can find no record of Copper oxide forming an Orthosilicate. The
Phase diagram, Cu2O. SiO2, Fig 164 in the ACerS book (1979) implies
that the two liquids are not miscible and do not react with each
other.
Best regards,
Ivor Lewis.
Redhill,
South Australia.

Ivor and Olive Lewis on sun 31 aug 08


Dear Marian,
Inspite of the wealth of knowledge you convey to us, you still fail to
give any information about a direct relationship between Copper oxide
and Silicon dioxide.
Eliminate all those rare minerals from your list that contain Water or
Hydroxyl ions and other elements and what remains that might interest
a potter?
All I ask is, Why is it possible for the Oxide of the element Zinc to
form a stable, useful, decorative silicate when the oxides of its next
door neighbour in the Periodic Table, Copper, seems to resist chemical
union with Silicon dioxide to create a Silicate of the form CuSiO3.
Imagine the stir it would create among potters if they could achieve
the colours of other Copper compounds, like Blue Vitriol
Seems like a simple question to me.
Perhaps this is something that Chemists cannot explain.
Sincere regards,
Ivor Lewis.
Redhill,
South Australia.

jean szostek on mon 1 sep 08


hi ivor,
the last kiln i fired i had a plate that was light blue with turqoise - is
that the blue you mean by blue vitriol - sorry that i don't have a pix from
it, the first fair i did two days later the plate was sold
greatings jean
----- Original Message -----
From: "Ivor and Olive Lewis"
To:
Sent: Sunday, August 31, 2008 9:36 AM
Subject: Mysterious bubbles, satin with copper carbonate


> Dear Marian,
> Inspite of the wealth of knowledge you convey to us, you still fail to
> give any information about a direct relationship between Copper oxide
> and Silicon dioxide.
> Eliminate all those rare minerals from your list that contain Water or
> Hydroxyl ions and other elements and what remains that might interest
> a potter?
> All I ask is, Why is it possible for the Oxide of the element Zinc to
> form a stable, useful, decorative silicate when the oxides of its next
> door neighbour in the Periodic Table, Copper, seems to resist chemical
> union with Silicon dioxide to create a Silicate of the form CuSiO3.
> Imagine the stir it would create among potters if they could achieve
> the colours of other Copper compounds, like Blue Vitriol
> Seems like a simple question to me.
> Perhaps this is something that Chemists cannot explain.
> Sincere regards,
> Ivor Lewis.
> Redhill,
> South Australia.


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16:59

Neon-Cat on mon 1 sep 08


Ivor, I gave you an inosilicate of copper:
Shattuckite, Cu5(SiO3)4(OH)2, Copper Silicate Hydroxide. It's a single chain
inosilicate and an example of copper combining with the basic Si unit of
SiO3 (-2). Another example of a copper inosilicate is Plancheite,
Cu8Si8O22(OH)4 - H2O, Hydrated Copper Silicate Hydroxide. For zinc minerals
in the inosilicate class we have Gageite, (Mn,Mg,Zn)42Si16O54(OH)40,
Manganese Magnesium Zinc Silicate and Petedunnite, Ca(Zn,Mn++,Fe++,Mg)Si2O6,
Calcium Zinc Manganese Iron Magnesium Silicate.

When last you wrote you mentioned cobalt oxide, copper carbonate, and Cobalt
Orthosilicate and bemoaned the fact you were unable to find a copper oxide
forming an orthosilicate. I wondered then why you were stuck on
orthosilicates.

Ivor wrote before:
"The contrast between the sample coloured with Cobalt oxide and that
coloured with Copper Carbonate reminded me that I have a list on the desk
relating to the Transitional Metal oxides and their behaviour
towards silicate melts. Cobalt oxide is soluble in silicate melts, forming a
solution colour. It also reacts to form Cobalt Orthosilicate. I can find no
record of Copper oxide forming an Orthosilicate. The Phase diagram, Cu2O.
SiO2, Fig 164 in the ACerS book (1979) implies that the two liquids are not
miscible and do not react with each other."

Now you write:
"Inspite of the wealth of knowledge you convey to us, you still fail to give
any information about a direct relationship between Copper oxide and Silicon
dioxide. Eliminate all those rare minerals from your list that contain Water
or Hydroxyl ions and other elements and what remains that might interest a
potter? All I ask is, Why is it possible for the Oxide of the element Zinc
to form a stable, useful, decorative silicate when the oxides of its next
door neighbour in the Periodic Table, Copper, seems to resist chemical union
with Silicon dioxide to create a Silicate of the form CuSiO3. Imagine the
stir it would create among potters if they could achieve the colours of
other Copper compounds, like Blue Vitriol Seems like a simple question to
me. Perhaps this is something that Chemists cannot explain."

Ivor, I have four huge problems with your postings:
1. your questions are often unclear.
2. kaolin (kaolinite), one of our more common glaze materials will become
amorphous at 550 C/ 1022 F - you seem to expect nice, neat, simple,
crystalline copper (and other metal) silicates to form after we've fired the
bejeezus out of our starting materials. Dana has 9 major classes of
minerals. The silicate class is divided into Silicate Classes based on the
degree of polymerization of the silica tetrahedral unit (SiO4)(-4). A better
and more utilitarian system in use for clay minerals (phyllosilicates)
classification is one by the Association Internationale pour l'Etude des
Argiles (AIPEA) and the International Mineralogical Association (IMA).
3. Your terminology and definitions and seeming knowledge in both chemistry
and mineralogy leave something to be desired.
4. Both copper carbonate and copper oxides are going to reduce to copper
metal. Yet you insist on "seeing" some chemical reaction between a copper
oxide and silicon dioxide in the kiln. Much of our silica is bound up in
clay lattices and does not take the simple form (SiO2) found in quartz and
feldspars (they're in the tectosilcate class, also called framework
silicates). A familiarity with either Dana's classification system or the
newer AIPEA would make this clear to you. You often toss Dana around - use
that, it will work almost as well as the newer AIPEA system.

Orthosilicates are also called Neosilicates or "Island Silicates". Why?
Because as a class of silicate minerals they have a specific shared
characteristic - independent silica tetrahedral units. The basic Si unit is
the SiO4 (-4) polyhedron. The SiO4 tetrahedra do not share oxygen atoms with
neighboring tetrahedral units (each other). Instead, the individual silica
tetrahedral are linked to one another by metal cations in CN=6 (octahedral
coordination).

In some old dictionaries chrysocolla is referred to as cooper orthosilicate.
Chrysocolla (hydrated copper silicate) is CuSiO3 - nH2O or written more
correctly as (Cu,Al)2H2Si2O5(OH)4 . nH2O. It is most often amorphous (no
uniform crystalline structure) but sometimes found in a layered kaolinite
structure composed of tetrahedral and octahedral nets. So, although it can
be found with a written formula CuSiO3 - nH2O it is neither an orthosilicate
nor an inosilicate (also called neosilicate).

An example of a copper neosilicate (orthosilicate) is Cuprosklodowskite,
Cu(UO2)2Si2O7 - 6H2O, Hydrated Copper Uranyl Silicate. Common examples
(non-copper bearing) include garnet, staurolite, topaz, zircon, olivine, and
Willemite (zinc silicate, Zn2SiO4).

So, do not be mislead by a written chemical formula. Petedunnite, CaZnSi2O6,
a zinc clinopyroxene from the inosilicate class is an example of a zinc
mineral involving the SiO3 unit. ZnSiO3, zinc (II) metasilicate, is rather
an uncommon compound. Please tell me which zinc compound you are referring
to as a "stable, useful, decorative silicate" involving SiO3 that you'd
prefer copper to emulate. And please tell me what it is you expect from
copper. I have proven to you that copper does indeed form a wide variety of
copper silicates. Why you insist on a simple copper orthosilicate is a
mystery to me. The formation and structure of complex ionic/covalent crystal
bonds for what we might be creating in the kiln are governed by Pauling
rules (Linus Pauling, J. Am. Chem. Soc. 51, 1010, 1929), and the formation
of solid solutions is also regulated by Pauling rules, principally rule
number one. And we mustn't forget out friend aluminum, or any of the other
things we've added to our glaze - they will be taking part in structures and
reactions, or competing to do so. I hope this helps you in your quest for
greater understanding. Of course, we may just have copper or any other metal
in an exchange or substituted position within any crystalline structure
created or we may simply have an amorphous glaze with captured elements.
Mirroring our natural world of minerals, any products created in our kilns
are not likely to be simple structures. That we have created some type of
silicate or colloidal particle is enough for most of us to know. Most of us
just want a nice workable and repeatable glaze, color and all. Here is where
the sharing of tried and true glaze recipes helps to anchor our art and
craft.

I wish you luck creating that perfect Blue Vitriol (CuSO45 H2O, copper II
sulfate, pentahydrate) like glaze color. The beautiful blue color you seem
fond of results from water molecules that are attached directly to the
copper II ion - not something we'll see after firing. Potters do and have
over the centuries created beautiful blues that we can all appreciate.

Happy Labor Day, fellow Americans! Happy Monday to everyone else!

Marian,
back to my now overly dry ceramic creation ...

Steve Slatin on mon 1 sep 08


Jean --

He probably means the color of copper sulphate.
The mineral chalcanthite has the color and
is mostly hydrated copper sulphate; any decent
rock shop will have a sample. 'Blue vitriol'
is a fairly obsolete term in the U.S.; I guess
it's still current in Australia.

Steve Slatin --




--- On Mon, 9/1/08, jean szostek wrote:

> hi ivor,
> the last kiln i fired i had a plate that was light blue
> with turqoise - is
> that the blue you mean by blue vitriol - sorry that i
> don't have a pix from
> it, the first fair i did two days later the plate was sold
> greatings jean

Ivor and Olive Lewis on tue 2 sep 08


Dear Jean Szostek ,
If it is a clear blue without any hint of green or violet, then what
you have may very well have the colour that matches the colour of
Copper Sulphate Pentahydrate.
Thank you for your note.
Best regards,
Ivor Lewis.
Redhill,
South Australia.

Des & Jan Howard on tue 2 sep 08


Ivor
Something like these?
http://www.luepottery.hwy.com.au/clayartpics.htm

Just teasing, these aren't copper, instead they're
cobalt magnesia blue over temmoku.
Des

Ivor and Olive Lewis wrote:
> If it is a clear blue without any hint of green or violet, then what
> you have may very well have the colour that matches the colour of
> Copper Sulphate Pentahydrate.

--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850

02 6373 6419
www.luepottery.hwy.com.au

Neon-Cat on sun 7 sep 08


Josh, "the fuzzy" wrote: "No?"

Yes, Josh, feel free to try the oxide.
Wouldn't hurt if you have a mind to experiment -- the carbonate's performing
poorly for you anyway.
The copper oxides are a very volatile pair, lots of back and forth between
the copper I and copper II ion or ion-complexes having to do with
equilibrium states and temperature fluctuations, among other things. By
using the oxide you skip the bubbles and get right down to letting the
copper oxides tussle over who will predominate. Cobalt and its species are a
tad tamer than the copper family and tend to form more stable complexes.
Probably why you notice that the bubbling from cobalt carbonate has a better
chance to "heal" during your particular firing schedule than its copper
carbonate buddy. Rather interesting but I'm jones-ing for clay right now and
don't wish to fully engage in science tonight.
Let us know what happens if you try the copper oxide substitution in your
glaze recipe; I'm a little curious. Try both forms, red and black if you
have them. Add a little interest to our lives by reporting back. But I'm
actually more curious about your signature tag "the fuzzy", taking me even
further afield from contemplating the glaze melt.

Have fun!
Marian

Josh Berkus on sun 7 sep 08


Marion,

> To answer Josh's question, yes, all carbonates will bubble as they release
> carbon dioxide when heated. Many of our glazes "heal" during their time in
> the kiln but once in awhile we may see pinholes or blisters in glazes as
> the result of the off-gasing of carbon dioxide. Josh could lengthen his
> firing schedule slightly and see if that helps or switch to copper oxide
> for his glaze color. Others have made good suggestions in this direction.

Thanks. Unfortunately, I can't lenghten the hold period for that glaze,
because it would cause other of my glazes to run down to the foot. However,
that does suggest that I should try "rescuing" some of the existing
copper-glazed pieces by refiring them.

This does leave as a mystery, though, why the *copper* carbonate produced this
effect, but the *cobalt* carbonate, in the same % and the same base, did not.
As far as I know, CoCO3 is the same number of carbonate atoms as CuCO3.

Your chemistry lesson would imply, however, that I might be better off using
Copper Oxide instead of Carbonate as it would not form CO2 bubbles. No?

--
Josh "the Fuzzy" Berkus
San Francisco

The Fuzzy Chef on wed 10 sep 08


Marian,

> Let us know what happens if you try the copper oxide substitution in your
> glaze recipe; I'm a little curious. Try both forms, red and black if you
> have them. Add a little interest to our lives by reporting back.

I need to go out and buy them, so it won't be in the next firing.

> But I'm
> actually more curious about your signature tag "the fuzzy", taking me even
> further afield from contemplating the glaze melt.

Oh, thats easy. Here's a picture of me:

http://fuzzychef.smugmug.com/gallery/4148796_JG3B8/1/242160025_LMq8B/Medium

See? Fuzzy. "The Fuzzy" or "The Fuzband" to my wife.

I also have a food & pottery (but primarily food) blog up at
www.fuzzychef.org.

--Josh

Josh Berkus on tue 23 sep 08


Marian, Maid O' Mud:

Got my next set of tests back. =A0Using the Glossy Clear Liner with Copper=
=20
Carbonate didn't help much; the glaze is less satin, but just as foggy=20
with tiny bubbles. =A0However, switching from Copper Carbonate to Black=20
Copper Oxide with Glossy Base #2 did mostly work. =A0There's still some=20
bubbling where the glaze pools, but overall its the nice glossy green that=
=20
I wanted.

Related to this, I'm noticing a higher-than-expected rate of pinholing=20
among all of my glazes in general. =A0I'm wondering if maybe the claybody i=
s=20
at fault; it's Laguna B-Mix Cone 5. =A0Thoughts?

=2D-=20
Josh Berkus
San Francisco