Tony Ferguson on tue 7 sep 04
Ivor,
My recollection of sulphides is that they are very toxic and very soluable.
Please, anyone, correct me if I am wrong. My question, like Ivor's, is are
they any less toxic than some of the oxides we use?
Thank you.
Tony Ferguson
On Lake Superior, where the sky meets the Lake
Custom & Manufactured Kiln Design
Stoneware, Porcelain, Raku and more
by Coleman, Ferguson, Winchester...
http://www.aquariusartgallery.com
218-727-6339
315 N. Lake Ave
Apt 312
Duluth, MN 55806
----- Original Message -----
From: "Ivor and Olive Lewis"
To:
Sent: Tuesday, September 07, 2004 9:28 PM
Subject: Colouring Glazes. A New Idea.
Dear Friends,
Are there reasons why, apart from porcelain workers who use soluble salts,
are other insoluble compounds of Transition Metal Elements not used as
agents to colour our glazes.
We use Oxides and Carbonates. Why do we not use Sulphides ? Has anyone ever
heard of them being used?
Would using Sulphides or Phosphides get over some of the problems we may
experience with Copper, Nickel, Manganese and Chrome.
Just one of those off hand thoughts that come from dreaming.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
____________________________________________________________________________
__
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Ilene Mahler on wed 8 sep 04
wear gloves when using as they are toxic...Ilene in Conn
----- Original Message -----
From: "Tony Ferguson"
To:
Sent: Wednesday, September 08, 2004 12:32 AM
Subject: Re: Colouring Glazes. A New Idea.
> Ivor,
>
> My recollection of sulphides is that they are very toxic and very
soluable.
> Please, anyone, correct me if I am wrong. My question, like Ivor's, is
are
> they any less toxic than some of the oxides we use?
>
>
>
> Thank you.
>
> Tony Ferguson
> On Lake Superior, where the sky meets the Lake
>
> Custom & Manufactured Kiln Design
> Stoneware, Porcelain, Raku and more
> by Coleman, Ferguson, Winchester...
> http://www.aquariusartgallery.com
> 218-727-6339
> 315 N. Lake Ave
> Apt 312
> Duluth, MN 55806
>
>
>
>
> ----- Original Message -----
> From: "Ivor and Olive Lewis"
> To:
> Sent: Tuesday, September 07, 2004 9:28 PM
> Subject: Colouring Glazes. A New Idea.
>
>
> Dear Friends,
> Are there reasons why, apart from porcelain workers who use soluble
salts,
> are other insoluble compounds of Transition Metal Elements not used as
> agents to colour our glazes.
> We use Oxides and Carbonates. Why do we not use Sulphides ? Has anyone
ever
> heard of them being used?
> Would using Sulphides or Phosphides get over some of the problems we may
> experience with Copper, Nickel, Manganese and Chrome.
> Just one of those off hand thoughts that come from dreaming.
> Best regards,
> Ivor Lewis.
> Redhill,
> S. Australia.
>
>
____________________________________________________________________________
> __
> 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.
>
>
____________________________________________________________________________
__
> 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.
Steve Slatin on wed 8 sep 04
Ivor --
Haven't researched sulfur in this context, but from a
safety standpoint sulfur compounds are a nightmare.
Many are quite toxic, often they have extremely low
melting and decomposition points, not good
characteristics for material safety.
(Imagine what it'd do to the elements in an electric
kiln ... )
Of phosphides I know almost nothing, except for
Aluminum Phosphide, which is (to begin with) a rat
poison, and which in the presence of acids releases
hydrogen phosphide, which is pyrophoric and toxic
both.
Regards - Steve Slatin
--- Ivor and Olive Lewis
wrote:
> Dear Friends,
> Are there reasons why, apart from porcelain workers
> who use soluble salts, are other insoluble compounds
> of Transition Metal Elements not used as agents to
> colour our glazes.
> We use Oxides and Carbonates. Why do we not use
> Sulphides ? Has anyone ever heard of them being
> used?
> Would using Sulphides or Phosphides get over some of
> the problems we may experience with Copper, Nickel,
> Manganese and Chrome.
> Just one of those off hand thoughts that come from
> dreaming.
> Best regards,
> Ivor Lewis.
> Redhill,
=====
Steve Slatin -- Entry-level potter, journeyman loafer, master obfuscator
Sequim, Washington, USA
48.0937°N, 123.1465°W or thereabouts
__________________________________
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Ivor and Olive Lewis on wed 8 sep 04
Dear Friends,=20
Are there reasons why, apart from porcelain workers who use soluble =
salts, are other insoluble compounds of Transition Metal Elements not =
used as agents to colour our glazes.
We use Oxides and Carbonates. Why do we not use Sulphides ? Has anyone =
ever heard of them being used?
Would using Sulphides or Phosphides get over some of the problems we may =
experience with Copper, Nickel, Manganese and Chrome.
Just one of those off hand thoughts that come from dreaming.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
Ivor and Olive Lewis on thu 9 sep 04
Dear Steve Slatin,
Thanks for your comment.
If compounds that contain Sulphur in their composition are a
"nightmare" why do we make such free use of Gypsum ? And what about
the discharge of Sulphur oxides from clay when it is fired? Do we ever
think about that?
I have no doubt that the containers in which sulphide compounds are
distributed carry the requisite warnings to health and safety.
Monday "arvo" I was rolling south along Highway One and got tucked in
behind a pair of "double semi B" road trains. Yellow labels on the
backs of the containers caught my eye. Both were plastered with
Radioactivity warnings. Yellow Cake on the move. Mobile death on
wheels!!
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
Ivor and Olive Lewis on thu 9 sep 04
Dear Tony Ferguson,
Most metallic Sulphides have very low solubilities in water which is
why they persist in crustal rocks and become most valuable ore bodies,
especially Copper and Iron Sulphides (Fools Gold).
Toxicity becomes a problem when Sulphide compounds dissolve in acids
giving that "Rotten Egg" aroma of Hydrogen Sulphide. This is deadly
even if you inhale it for a short period of time because your sense of
smell is the first thing to suffer and the aroma fades away even
though the gas is still there in the atmosphere.
But we should not forget that some Sulphides are recommended as
starting points for Smoked Lustre.
So, like yourself, I wonder if there is any information about using
metallic sulphides in a general way for colouring glazes.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
Steve Slatin on thu 9 sep 04
Ivor --
You know lots more of the chemistry than I do, as I've
said before. And I'm not going to say you can't
figure out a way to use sulphur compounds in lieu of,
say, metal oxides. I do believe the problems of
sulfur are such that it remains impractical.
What's attractive about sulphur is that it's in the
same group as oxygen. What's unattractive is that
the stuff that burns off in a firing, if hydrogen-
linked, would be corrosive instead of
relatively 'friendly' like the oxygen compounds.
As for gypsum and why we use it in our homes, my
answer'd be that we don't fire our homes. I don't
know lots about gypsum, but if memory serves it's
CaSO4 and Quartz. The CaS04 has a fairly high
melting point (1450 C), so (for practical purposes, as
a building product) it remains inert. Also, we don't
subject our wallboard to chemical challenge,
generally we paint it to protect it from chemical
challenge.
It's quite different if you evaluate it as a component
in a firing, where temperatures approaching or
reaching the melting point are achievable.
Of course if the sulphur remains in the glaze after
the melt, that's different. Maybe sulphur itself
could be a part of the glaze. I don't know the
answer, it's a good question for someone with the
time to research it.
You ask the excellent question do we respond to
the risk of sulphur-compound outgassing in our clay
firing. Personally, I do. I stay the heck out of
my studio when I'm firing (bisque and glaze both).
And I keep windows open. And my studio was built
aligned to catch the wind, and has windows on
three sides and a door on the other {I like to think
of this as the Edouard Bastarache safety protocol.)
As for the yellowcake issue -- please don't draw me
into that one again. (I don't need the flames.)
Radioactivity is treated more seriously than other
hazards, largely because it's harder to visualize.
Best wishes --
Steve Slatin
--- Ivor and Olive Lewis
wrote:
> Dear Steve Slatin,
> Thanks for your comment.
> If compounds that contain Sulphur in their
> composition are a
> "nightmare" why do we make such free use of Gypsum ?
> And what about
> the discharge of Sulphur oxides from clay when it is
> fired? Do we ever
> think about that?
=====
Steve Slatin -- Entry-level potter, journeyman loafer, master obfuscator
Sequim, Washington, USA
48.0937°N, 123.1465°W or thereabouts
__________________________________
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Jocelyn McAuley on thu 9 sep 04
I'm coming into this thread a little delayed ...
The article in Ceramics Monthly about the use of rare earth elements
resparked my chemistry interests in the pursuit of unimagined ceramic
colors and surfaces. I too wondered about alternative coloring agents
that we have been overlooking.
I work in a research lab and do all of our chemical ordering. A couple
of times I have ordered from one of our chemical suppliers (Sigma) to
test out some of the rare earths. Some nice colors, but the tests come
out to be a bit pricey.
Arne Ase has a wonderful book, "Water Colour on Porcelain"
that contains several interesting facets. He doesn't explore sulphides,
however, he does go into his testing stategies for water souble
chlorides and nitrates. The list of chemicals he tests is quite
extensive... copper chloride, tellurium tetrachloride, and vanadyl
sulphate to name a few.
In addition to testing alternative compounds for coloring glazes, he
details his techniques for producing shellaced porcelain (including
images of his setters to prevent deformation as he fires his bowls
upside down), and a section of the role of research as it intermingles
with art and a section on creativity in general.
His book really is a multifaceted gem.
> So, like yourself, I wonder if there is any information about using
> metallic sulphides in a general way for colouring glazes.
Jocelyn McAuley
--
http://www.lucentarts.com
Ivor and Olive Lewis on fri 10 sep 04
Thanks Steve Slatin,
I recall a Master Potter of an industrial operation telling me that
the EPA people went mad about Sulphur gas emissions but never thought
to consider how much Fluorine came out of a kiln.
Metallic sulphides ! I was intrigued by the thought that sulphur
minerals, Pyrites and the like all have golden metallic lustre.
There are recipes for smoked lustre surfaces out there which
incorporate them. Perhaps the lustre people might like to comment .
Margery Clinton ("Lustres" edited by Emmanuel Cooper) give Franchet's
recipes as well as her own with both Silver and Copper sulphide as
ingredients.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
----- Original Message -----
From: "Steve Slatin"
To:
Sent: Friday, 10 September 2004 2:05
Subject: Re: Colouring Glazes. A New Idea.
> Ivor --
>
> You know lots more of the chemistry than I do, as I've
> said before. And I'm not going to say you can't
> figure out a way to use sulphur compounds in lieu of,
> say, metal oxides. I do believe the problems of
> sulfur are such that it remains impractical.
>
> What's attractive about sulphur is that it's in the
> same group as oxygen. What's unattractive is that
> the stuff that burns off in a firing, if hydrogen-
> linked, would be corrosive instead of
> relatively 'friendly' like the oxygen compounds.
>
> As for gypsum and why we use it in our homes, my
> answer'd be that we don't fire our homes. I don't
> know lots about gypsum, but if memory serves it's
> CaSO4 and Quartz. The CaS04 has a fairly high
> melting point (1450 C), so (for practical purposes, as
> a building product) it remains inert. Also, we don't
> subject our wallboard to chemical challenge,
> generally we paint it to protect it from chemical
> challenge.
>
> It's quite different if you evaluate it as a component
> in a firing, where temperatures approaching or
> reaching the melting point are achievable.
>
> Of course if the sulphur remains in the glaze after
> the melt, that's different. Maybe sulphur itself
> could be a part of the glaze. I don't know the
> answer, it's a good question for someone with the
> time to research it.
>
> You ask the excellent question do we respond to
> the risk of sulphur-compound outgassing in our clay
> firing. Personally, I do. I stay the heck out of
> my studio when I'm firing (bisque and glaze both).
> And I keep windows open. And my studio was built
> aligned to catch the wind, and has windows on
> three sides and a door on the other {I like to think
> of this as the Edouard Bastarache safety protocol.)
>
> As for the yellowcake issue -- please don't draw me
> into that one again. (I don't need the flames.)
> Radioactivity is treated more seriously than other
> hazards, largely because it's harder to visualize.
>
> Best wishes --
>
> Steve Slatin
>
>
> --- Ivor and Olive Lewis
> wrote:
>
> > Dear Steve Slatin,
> > Thanks for your comment.
> > If compounds that contain Sulphur in their
> > composition are a
> > "nightmare" why do we make such free use of Gypsum ?
> > And what about
> > the discharge of Sulphur oxides from clay when it is
> > fired? Do we ever
> > think about that?
>
> =3D=3D=3D=3D=3D
> Steve Slatin -- Entry-level potter, journeyman loafer, master
obfuscator
> Sequim, Washington, USA
> 48.0937=B0N, 123.1465=B0W or thereabouts
>
>
>
> __________________________________
> Do you Yahoo!?
> Yahoo! Mail - 50x more storage than other providers!
> http://promotions.yahoo.com/new_mail
>
>
______________________________________________________________________
________
> 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.
Ivor and Olive Lewis on sat 11 sep 04
Dear Jocelyn McAuley,
Thank you for your note.
I will try to get the Arne Ase book on interlibrary loan. Do you have
the ISBN code?
Yes, I do have some of the Rare Earth oxides, courtesy of an Austrian
Company. I think they would have greater use as tinting agents for
some of the more prominent colours we use and vice versa.
The only notes I have read about using Sulphide compounds is with
reference to Smoked Lustres and there are so few people using this
technique that I don't think the toxic issues are of concern in a
general way. Anyway, that process is still in the land of Alchemy when
it comes to understanding how it works.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
Kathy Forer on sat 11 sep 04
Is there any known crossover between bronze and metal patination and
clay glazing? Metal patinas are very involved with sulphides and
natural oxides.
http://www.amazon.com/exec/obidos/tg/detail/-/0823007626
Kathy Forer
Jocelyn McAuley on sat 11 sep 04
ISBN 82-00-06524-3
Arne Ase, Water Colour on Porcelian
I occasionally visit Powell's bookstore in Portland, Oregon, which is a
mecca for used books. I have seen this book there before... so I will
make it a point to pick up the next one I see and offer it on the list.
My library here fits my needs, no need to hoard more art books.
Best of luck
Jocelyn
Ivor and Olive Lewis wrote:
> Dear Jocelyn McAuley,
> Thank you for your note.
> I will try to get the Arne Ase book on interlibrary loan. Do you have
> the ISBN code?
> Yes, I do have some of the Rare Earth oxides, courtesy of an Austrian
> Company. I think they would have greater use as tinting agents for
> some of the more prominent colours we use and vice versa.
> The only notes I have read about using Sulphide compounds is with
> reference to Smoked Lustres and there are so few people using this
> technique that I don't think the toxic issues are of concern in a
> general way. Anyway, that process is still in the land of Alchemy when
> it comes to understanding how it works.
> Best regards,
> Ivor Lewis.
> Redhill,
> S. Australia.
>
--
http://www.lucentarts.com
Snail Scott on sun 12 sep 04
At 02:01 PM 9/12/2004 -0400, you wrote:
>I was thinking of the kind of active bronze patinas where you mix, then
>spray or paint, let's say, liver of sulfur on bronze to get a brown
>base, and apply heat with a torch, then brush or spray Copper sulfate
>(blue vitriol) and more heat. Each layer makes a chemical change to the
>underlying metal.
Actually, typical hot chemical patinas on
bronze do NOT induce any chemical change
in the metal. It is closer to the mark
to say the the chemicals are fused to the
surface of the hot metal, and are
generally converted, (at least in part)
to an oxide.
(I did this for a living for quite a while.)
-Snail Scott
Dorothy Feibleman on sun 12 sep 04
There is information on this subject on the internet in great detail, since
the book is no longer available and althought I tried to get one big
publisher to re-publish it, they said it was too detailed, too long--but
that was(maybe 5-8 years ago) before so many new ones came out and maybe a
publisher would bring it out again. I have the book in my library room, but
I have a guest there and they are sleeping, if you want the number, I can
give it to you tomorrow. She just woke up--ISBN 82-00-06524-2 Norwegian
University Press."Water Colour on Porcelain" You might get it off the
internet in a used book site.
What makes the lines is how it goes into the clay and how it gathers on the
surface and in the clay, hence the unusual effect.
Also about all the chemicals, look on the internet, you`d be surprised.
The rare earth oxides are also available over the internet many companies
are using them presently, especially in China, but in other ways, not
"pots". they are expensive for delicate colours, unless maybe you decide to
do tons of testing and find that a very small amount of degussa pink/red is
actually cheaper than a large amount of a rare earth that might give a hint
of pink--both are translucent .
best d
>Dear Jocelyn McAuley,
>Thank you for your note.
>I will try to get the Arne Ase book on interlibrary loan. Do you have
>the ISBN code?
>Yes, I do have some of the Rare Earth oxides, courtesy of an Austrian
>Company. I think they would have greater use as tinting agents for
>some of the more prominent colours we use and vice versa.
>The only notes I have read about using Sulphide compounds is with
>reference to Smoked Lustres and there are so few people using this
>technique that I don't think the toxic issues are of concern in a
>general way. Anyway, that process is still in the land of Alchemy when
>it comes to understanding how it works.
>Best regards,
>Ivor Lewis.
>Redhill,
>S. Australia.
>
>______________________________________________________________________________
>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.
Earl Krueger on sun 12 sep 04
Ron,
Everyone has seen the "Periodic Table of Elements"
hanging in their science classroom. This is more than
just a pretty poster! :-)
The periodic table was first published in 1869 by
Dmitri Mendeleev as a tool to predict the existence
and properties of unknown elements. It still is useful
today to predict the properties of elements. The
solubility of the sulphates of the Group II alkaline
earths make a good case in point.
We all know that calcium sulphate is somewhat
soluble in water and that barium sulphate is much
less so. But what about strontium sulphate?
Go to: http://www/webelements.com and see what
you can predict.
If we look at the vertical Group II column we see that in
order of increasing atomic number the elements are:
berylliumSince we know that:
1. calcium sulphate is less soluble than barium sulphate,
2. strontium lies between calcium and barium in the table
then we can predict that strontium sulphate will have a
solubility somewhere between calcium sulphate and
barium sulphate. We might also predict that magnesium
and beryllium sulphates will be more soluble than calcium.
Doing a little research I came up with some numbers for
grams of material that will dissolve in 100 grams of water
for the Group II sulphates:
Beryllium 43.8
Magnesium 29.0
Calcium 0.20
Strontium 0.0114
Barium 0.000285
Radium 0.000002
Was your prediction right?
Since strontium sulphate has only 1/18 the solubility of
calcium sulphate it may work quite well for tying up the
sulphates in scummy clay without the toxicity problems
of barium.
Anyone care to try this out and report back?
Of course radium would be the best, in terms of making
the sulphate insoluble, but its use is problematic.
1. It would be difficult for a potter to obtain,
2. The radioactivity would lead to a short career,
3. Buyers may be put off by the required labeling of your pots.
But Oh how wonderful glow-in-the-dark pots would be.
Just imagine a darkened gallery with elegantly formed
pots radiating a beautiful greenish glow. :-)
Earl K...
Bothell, WA, USA
Ivor and Olive Lewis on sun 12 sep 04
Dear Kathy Forer,
The simple link I can recall is Enamelling.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
Kathy Forer on sun 12 sep 04
On Sep 12, 2004, at 1:37 AM, Ivor and Olive Lewis wrote:
> The simple link I can recall is Enamelling.
like this? http://www.glass-on-metal.com/pastart/raku-tudor.htm
Unless it's on "metal clay," enameling seems to be glass on metal or
clay, fused by frits, using either a kiln or a torch.
I was thinking of the kind of active bronze patinas where you mix, then
spray or paint, let's say, liver of sulfur on bronze to get a brown
base, and apply heat with a torch, then brush or spray Copper sulfate
(blue vitriol) and more heat. Each layer makes a chemical change to the
underlying metal.
Or you mix all the ingredients at the same time, i.e. Ammonium Sulfate
(sal ammoniac), Copper sulfate (blue vitriol) Concentrated Ammonia, tap
water, then spray or brush and heat.
A similar chemical conversion of clay is different than an added layer
of material. My guess is raku is the closest similar process.
Kathy
Kathy Forer on mon 13 sep 04
On Sep 13, 2004, at 11:20 PM, Kathy Forer wrote:
> Not so much semantically, but functionally.
Can that. They're really the same thing. You won't be pouring milk in a
jug that's been finished with a "cold" finish. Any kind.
Kathy
Gary Elfring on mon 13 sep 04
DF> Also about all the chemicals, look on the internet, you`d be surprised.
DF> The rare earth oxides are also available over the internet many companies
DF> are using them presently, especially in China, but in other ways, not
DF> "pots". they are expensive for delicate colours, unless maybe you decide to
DF> do tons of testing and find that a very small amount of degussa pink/red is
DF> actually cheaper than a large amount of a rare earth that might give a hint
DF> of pink--both are translucent .
I have been working with the rare earth chemicals as colorants for the
last 6 months. They are currently not much more expensive than Cobalt
Oxide is. Cobalt Oxide was running $30/lb while Erbium Oxide is $35,
Neodymium Oxide $40/lb, and Praseodymium Oxide $25/lb. (All from US
Pigment Corp in Bloomingdale IL)
You do tend to use more of the rare earths- typically 3% - 8%, but you
get colors you can't really get any other way.
--
Best regards,
Gary
Hank Murrow on mon 13 sep 04
On Sep 12, 2004, at 9:29 PM, Earl Krueger wrote:
> But Oh how wonderful glow-in-the-dark pots would be.
> Just imagine a darkened gallery with elegantly formed
> pots radiating a beautiful greenish glow. :-)
Dear Earl;
I have seen this! Jon Singer, who mostly lurks here on Clayart, has
been busy making pots which glow under ultraviolet light. He has an
article coming out in the fall in Clay Times, and another in Studio
Potter, so look for them.
Can you visualize porcelains which glow pink, red, yellow, green, and
blue? I have seen this!
Cheers, Hank in Eugene
murrow.biz/hank
Kathy Forer on mon 13 sep 04
On Sep 12, 2004, at 11:42 PM, Snail Scott wrote:
> Actually, typical hot chemical patinas on
> bronze do NOT induce any chemical change
> in the metal. It is closer to the mark
> to say the the chemicals are fused to the
> surface of the hot metal, and are
> generally converted, (at least in part)
> to an oxide.
>
Would chemicals fuse to ceramic? Would a metal-style chemical patina on
bisque or even over glazed clay be considered a "cold finish"? Not so
much semantically, but functionally.
("Is there any point" is a whole 'nother question.)
Kathy
Kathy Forer on tue 14 sep 04
On Sep 14, 2004, at 10:29 AM, Snail Scott wrote:
> Yes, I have applied bronze-style chemical torch
> patinas to fired clay.
>
> What do you mean by a 'functionally' cold finish,
> though? What function do you have in mind?
Although I tried to retract my statement splitting functional and
semantic, I think I meant it "functionally" because it is seems to be a
"hot" finish, using a torch. If the chemicals actually bond with the
clay, and even interact with some different qualities, I thought that
might be more like a glaze than a cold finish which are more of a skin,
except stains.
> It is probably long-term stable, at least as much
> as on bronze and probably more, since the biggest
> cause of changes to bronze patinas is the reactivity
> of the underlying metal. It is moderately durable,
> but not like a glaze. Abrasion will scar it if it's
> on a smooth hard surface like glaze. (On bare clay,
> it pretty much soaks in.) I wouldn't eat off it,
> though!
I'd like to try a metal patina on bisque sometime, though raku may be
more efficient for getting similar effects. It just takes longer and
you don't always get to hold the torch.
There's so much to do, to try!
Kathy
Snail Scott on tue 14 sep 04
>On Sep 12, 2004, at 11:42 PM, Snail Scott wrote:
>> Actually, typical hot chemical patinas on
>> bronze do NOT induce any chemical change
>> in the metal. It is closer to the mark
>> to say the the chemicals are fused...
At 11:20 PM 9/13/2004 -0400, Kathy Forer wrote:
>Would chemicals fuse to ceramic? Would a metal-style chemical patina on
>bisque or even over glazed clay be considered a "cold finish"? Not so
>much semantically, but functionally.
Yes, I have applied bronze-style chemical torch
patinas to fired clay.
What do you mean by a 'functionally' cold finish,
though? What function do you have in mind?
It is probably long-term stable, at least as much
as on bronze and probably more, since the biggest
cause of changes to bronze patinas is the reactivity
of the underlying metal. It is moderately durable,
but not like a glaze. Abrasion will scar it if it's
on a smooth hard surface like glaze. (On bare clay,
it pretty much soaks in.) I wouldn't eat off it,
though!
-Snail Scott
Snail Scott on wed 15 sep 04
At 11:52 PM 9/14/2004 -0400, Kathy F wrote:
>If the chemicals actually bond with the
>clay, and even interact with some different qualities, I thought that
>might be more like a glaze than a cold finish which are more of a skin,
>except stains...
Unfortunately, hot patinas are done in about
the same heat range as a clothes iron - not
even close to red heat. It's not likely to
chemically bond to an underlying glaze or
clay.
>I'd like to try a metal patina on bisque sometime, though raku may be
>more efficient for getting similar effects.
If by that you mean metallic, remember that
patinas on metal get their gleam from the
metal itself. Patina chemicals over clay will
be as flat as the clay is.
There are some products available which involve
coating the clay (or other surface) with a
copper-bearing 'paint', which then creates a
surface receptive to _cold_ patina processes.
I'm told that it can also work with hot
processes, but I haven't used it. (Sculpt-
Nouveau is a manufacturer - their website
has a decent description.)
I would still not even consider using this as
a food surface.
-Snail Scott
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