Paulette Carr on mon 14 apr 08
To all Colored Clay experts:
I have previously colored a high-fire clay, non-porcelain "white"
clay body, and had wonderful results. I am now interested in
coloring a low-fire talc clay body, but have read somewhere, or have
the impression that the colors are not as intense per gram of stain ,
and I do not want to use raw oxides. Is this the case? I am ready
to jump in with both feet, but since it is a relatively expensive
proposition, I was hoping for some advise.
Thanks, in advance, for any (coloring) pearls of wisdom that you can
share!
My best,
Paulette Carr
Paulette Carr Studio
St. Louis, MO
Member, Potters Council
Vince Pitelka on mon 14 apr 08
Paulette Carr wrote:
"I have previously colored a high-fire clay, non-porcelain "white"
clay body, and had wonderful results. I am now interested in
coloring a low-fire talc clay body, but have read somewhere, or have
the impression that the colors are not as intense per gram of stain ,
and I do not want to use raw oxides. Is this the case? I am ready
to jump in with both feet, but since it is a relatively expensive
proposition, I was hoping for some advise."
Paulette -
When I started using colored clays I was doing low-fired work exclusively,
and when I wanted deeply saturated colors it took a lot of stain. It is
true that the higher you fire, the less stain you need to achieve the same
level of saturation. In some of the pictorial inlaid colored clay pieces I
did twenty years ago, I wanted to achieve a pitch-black night sky, and it
required 25% Mason 6600 best black to achieve the depth of black I sought.
You can see examples on the "early work" section of the "gallery" page at my
website. The platter called "Night Machines" at
http://iweb.tntech.edu/wpitelka/gallery/early%20work/early-2.htm is a good
example. I used about a pound of Best Black to three pounds of white
earthenware clay, so that was some expensive clay.
All of the colored clay work I am doing today is soda-fired to cone 6, and
the darker colors in the patterned loaves I made twenty years ago come out
quite dark. I have backed off on the amount of colorant I use. It is hard
for me to tell you specifically how much to use, because I mix colored clays
by the color of the resulting clay, rather than by percentages. The best
thing would be for you to do a series of tests with colorant additions in
increments of 3% - so, to equal amounts of clay, add 3%, 6%, 9%, 12%, and
15% of stain, and fire to the intended maturation temperature. It will be
worth your while to do lots of these tests. The easiest way to add the
colorant is to slice the clay, dry it completely, immerse it in water to
slake it down to slurry, blend with a drill-mounted impeller mixer, divide
it into batches, mix in the stains with the same impeller mixer, and then
stiffen the clays back to plastic consistency.
The cost of doing colored clay work of course depends on how you use your
colored clays. In my work, the laminated colored clays are a veneer only
about 1/32" thick laminated to a core of plain clay, so my patterned loaves
give me a lot of coverage, and the cost is minimal.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Bryan on mon 14 apr 08
Paulette Carr wrote:
> I am now interested in
> coloring a low-fire talc clay body, but have read somewhere, or have
> the impression that the colors are not as intense per gram of stain ,
It seems like the intensity, for a given amount of pigment, is
proportional to the amount of vitrification.
How different is a low fire talc body from a bisqued piece?
Bryan Johnson
Curtis Benzle on tue 15 apr 08
A low fire talc body should yield a darker color when fired to maturity than
a
bisqued piece. It has to do with the vitrification and the talc body fired
to maturity
should be more vitreous. I have fired colored porcelain to cone 8 (for 30+
years) and
the highest colorant percentage I use is 10% for Mason 6600 black. It
yields
a jet black(at maturity...). No matter what clay you use, if you fire it
close to
maturity you should be able to cut the stain percentage back to no more than
10 %.
Vince's comments are dead on. Also note that the higher the stain
percentage of black
you use the more the clay will vitrify. The stain is a catalyst. This could
mess up your
compatibility if you are using the nerikomi technique.
Curt
On Mon, Apr 14, 2008 at 8:06 PM, Bryan wrote:
> Paulette Carr wrote:
>
> > I am now interested in
> > coloring a low-fire talc clay body, but have read somewhere, or have
> > the impression that the colors are not as intense per gram of stain ,
> >
>
>
> It seems like the intensity, for a given amount of pigment, is
> proportional to the amount of vitrification.
> How different is a low fire talc body from a bisqued piece?
>
> Bryan Johnson
>
>
>
> ______________________________________________________________________________
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, change your
> subscription settings or unsubscribe/leave the list here:
> http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots2@visi.com
>
Eleanora Eden on tue 15 apr 08
Hi Paulette,
I'm not a colored clay expert but I have done tests from time to time.
I just looked back in my notebooks and see that I used 8% of turquoise
Mason stain to color a slip body a nice robin's egg blue. My recollection
is that 10% gets you a recognizable pastel. Its for strong colors that
you have to get up in the 20% range.
Definitely you don't get as much bang for the buck as with glaze, but
of course you are coloring the whole body and not just the thin veneer.
I'm talking about using white earthenware firing bisq ^04 / glaze ^06.
Best,
Eleanora
>To all Colored Clay experts:
>
>I have previously colored a high-fire clay, non-porcelain "white"
>clay body, and had wonderful results. I am now interested in
>coloring a low-fire talc clay body, but have read somewhere, or have
>the impression that the colors are not as intense per gram of stain ,
>and I do not want to use raw oxides. Is this the case? I am ready
>to jump in with both feet, but since it is a relatively expensive
>proposition, I was hoping for some advise.
>
>Thanks, in advance, for any (coloring) pearls of wisdom that you can
>share!
>
>My best,
>Paulette Carr
--
Bellows Falls Vermont
www.eleanoraeden.com
Paulette Carr on tue 15 apr 08
Bryan,
Thank you for confirming my suspicions that the intensity of the
colored clay will be less per gram of commercial stain for a low-fire
clay body. My clay is fired to ^03, and differs from a bisque piece
made from a higher firing clay in that my absorption is around 10%,
and the absorption of the higher firing bisque piece is probably much
higher. In addition, the absorption of my clay body never goes lower
(and this is as vitrified as this claybody will ever become - I did
test it), and if I do fire high enough - around ^1 or so, the piece
will slump/melt, since talc will become a flux. So this clay body is
a different animal than a bisqued piece (made from a clay body with
higher temperature maturation) - and a different animal than
terracotta low-fire clay bodies.. I am not only stuck with the lower
temperature, I choose to work here for environmental reasons... just
have to find a way to get what I want. I will have to run tests to
find the correct percentages for the intensity and colors in which I
am interested, and it does seem doable.
My best,
Paulette
Paulette Carr Studio
St. Louis, MO
Member, Potters Council
Bryan Johnson wrote:
"It seems like the intensity, for a given amount of pigment, is
proportional to the amount of vitrification. How different is a low
fire talc body from a bisqued piece?"
Paulette Carr on tue 15 apr 08
Vince,
Wow - this is more than I hoped for! Thanks so much for the detailed
information and procedures! I will do the tests that you suggest,
and know that for the intensity of black that you have in your
platters, I would need roughly 25% Mason 6600. Your clay marquetry
is exquisite! I was hoping to work with agateware and inlays... your
work is really an inspiration! If this turns out to be just too
expensive, then I will consider lamination and slip painting. As
soon as I finish my mural (hopefuly late this summer), I will be
looking for one of your workshops. The first step, however, it to
find the percentages necessary for the colors and intensities that I
want. Off to work...
My best,
Paulette
Paulette Carr Studio
St. Louis, MO
Member, Potters Council
Vince Pitelka wrote:
"When I started using colored clays I was doing low-fired work
exclusively,
and when I wanted deeply saturated colors it took a lot of stain. It is
true that the higher you fire, the less stain you need to achieve the
same
level of saturation. In some of the pictorial inlaid colored clay
pieces I
did twenty years ago, I wanted to achieve a pitch-black night sky,
and it
required 25% Mason 6600 best black to achieve the depth of black I
sought.
You can see examples on the "early work" section of the "gallery"
page at my
website. The platter called "Night Machines" at
http://iweb.tntech.edu/wpitelka/gallery/early%20work/early-2.htm is a
good
example. I used about a pound of Best Black to three pounds of white
earthenware clay, so that was some expensive clay.
All of the colored clay work I am doing today is soda-fired to cone
6, and
the darker colors in the patterned loaves I made twenty years ago
come out
quite dark. I have backed off on the amount of colorant I use. It
is hard
for me to tell you specifically how much to use, because I mix
colored clays
by the color of the resulting clay, rather than by percentages. The best
thing would be for you to do a series of tests with colorant
additions in
increments of 3% - so, to equal amounts of clay, add 3%, 6%, 9%, 12%,
and
15% of stain, and fire to the intended maturation temperature. It
will be
worth your while to do lots of these tests. The easiest way to add the
colorant is to slice the clay, dry it completely, immerse it in water to
slake it down to slurry, blend with a drill-mounted impeller mixer,
divide
it into batches, mix in the stains with the same impeller mixer, and
then
stiffen the clays back to plastic consistency.
The cost of doing colored clay work of course depends on how you use
your
colored clays. In my work, the laminated colored clays are a veneer
only
about 1/32" thick laminated to a core of plain clay, so my patterned
loaves
give me a lot of coverage, and the cost is minimal."
Paulette Carr on wed 16 apr 08
Curt,
Thank you for the information. That is very encouraging. I was
about to abandon testing the lower concentrations of black stain, but
I will now included them to make certain that I am not adding more
than I need for saturation. If I understand what you are saying with
regard to higher percentages of black, the colored clay body will
have a lower absorption with the colorant than without it. Talc
bodies are "odd" in that, unlike other clay bodies they do not seem
to decrease the absorption until they approach melting. I have found
that this body maintains it's 10% absorption from ^04 - ^01, and then
begins to deform around ^1. So, I have made the assumption that my
pieces are "mature" when fired to ^03. Are you suggesting that the
high percentages of black stain will cause the clay to deform at
lower heatwork, or will it reduce the absorption without
deformation? Perhaps, someone with technical knowledge of talc
bodies will weigh in on the maturation/vitrification behavior of
these clay bodies. I will keep the compatibility issue in mind.
My best,
Paulette
Paulette Carr Studio
St. Louis, MO
Member, Potters Council
Curtis Benzle wrote:
A low fire talc body should yield a darker color when fired to
maturity than a bisqued piece. It has to do with the vitrification
and the talc body fired
to maturity should be more vitreous. I have fired colored porcelain
to cone 8 (for 30+ years) and the highest colorant percentage I use
is 10% for Mason 6600 black. It yields a jet black(at maturity...).
No matter what clay you use, if you fire it close to
maturity you should be able to cut the stain percentage back to no
more than 10 %.
Vince's comments are dead on. Also note that the higher the stain
percentage of black you use the more the clay will vitrify. The
stain is a catalyst. This could mess up your compatibility if you are
using the nerikomi technique.
Vince Pitelka on wed 16 apr 08
Curtis Benzle wrote:
"Also note that the higher the stain percentage of black you use the more
the clay will vitrify. The stain is a catalyst."
Ivor Lewis wrote:
"This is an interesting idea. Given the common usage of the term "Catalyst"
as a substance that promotes a faster rate of a chemical reaction without
itself being changed in any way are you telling us that stains are not
integrated or dissolved into the materials in which they are mixed?"
Dear Ivor -
In some cases, it is an advantage to listen to what a person meant rather
than what they said. I understood exactly what Curtis meant, but I am not a
chemist, and I doubt that he is either. You are a chemist, and you noticed
the use of the word "catalyst, which I suppose was technically incorrect in
that context. I understood that he meant "flux." The darker brown and
black stains often contain large amounts of iron, and in highfiring might
flux the claybody and cause it to over-vitrify unless content of other
fluxes is adjusted.
I believe this is what Curtis was saying. Is that right Curtis?
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Ivor and Olive Lewis on wed 16 apr 08
Dear Curtis Benzle,
You say <<...Also note that the higher the stain percentage of black you =
use the more the clay will vitrify. The stain is a catalyst....>>
This is an interesting idea. Given the common usage of the term =
"Catalyst" as a substance that promotes a faster rate of a chemical =
reaction without itself being changed in any way are you telling us that =
stains are not integrated or dissolved into the materials in which they =
are mixed ?
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Curtis Benzle on wed 16 apr 08
Dear Ivor:
Not really..... I was going to use the word "melter" but it sounded funny.
for what ever reason, the black stain causes the clay to melt at a lower
rate---it's empirical....
Curt Benzle
benzleporcelain.com
On Wed, Apr 16, 2008 at 1:20 AM, Ivor and Olive Lewis
wrote:
> Dear Curtis Benzle,
>
> You say <<...Also note that the higher the stain percentage of black you
> use the more the clay will vitrify. The stain is a catalyst....>>
>
> This is an interesting idea. Given the common usage of the term "Catalyst"
> as a substance that promotes a faster rate of a chemical reaction without
> itself being changed in any way are you telling us that stains are not
> integrated or dissolved into the materials in which they are mixed ?
>
> Best regards,
>
> Ivor Lewis.
> Redhill,
> South Australia.
>
>
> ______________________________________________________________________________
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, change your
> subscription settings or unsubscribe/leave the list here:
> http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots2@visi.com
>
Ivor and Olive Lewis on thu 17 apr 08
Dear Curtis Benzle,
Thanks. I can live with that. I'm sure lots of things in the =
formulations we use interact in ways we can only speculate on.
Best regards,
Ivor
Ivor and Olive Lewis on fri 18 apr 08
Dear Vince,
Reading between the lines can keep things simple. But I took what I read =
at face value without imposing my own interpretation. Curtis has =
clarified things and I accept what he tells me without reservation
However, since you wish to take issue with me I accept your challenge. =
The information I have about prepared stains is that they are based on =
mixtures of various transitional metal oxides which have been heated to =
fusion to give stable compounds, many of which have similar molecular =
structures to the Spinel Group of Compounds. Typical characteristics of =
this group of substances are their resistance to heat, showing no =
indication of fusion under the action of the blowpipe, exceptional =
hardness of 8 on Mohs scale and a high degree of chemical inertness =
ensuring permanent physical attributes. Since these are single unique =
compounds, decomposition would be necessary to release Iron oxide. Then, =
if the temperature was high enough for a reaction between Ferrous Oxide =
and free silica the relatively low melting point compound 2FeO.SiO2 =
might form and enhance vitrification. But this would destroy the =
qualities of the stain.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
CurtisBenzle wrote:
"Also note that the higher the stain percentage of black you use the =
more
the clay will vitrify. The stain is a catalyst."
Ivor Lewis wrote:
"This is an interesting idea. Given the common usage of the term =
"Catalyst"
as a substance that promotes a faster rate of a chemical reaction =
without
itself being changed in any way are you telling us that stains are not
integrated or dissolved into the materials in which they are mixed?"
Dear Ivor -
In some cases, it is an advantage to listen to what a person meant =
rather
than what they said. I understood exactly what Curtis meant, but I am =
not a
chemist, and I doubt that he is either. You are a chemist, and you =
noticed
the use of the word "catalyst, which I suppose was technically incorrect =
in
that context. I understood that he meant "flux." The darker brown and
black stains often contain large amounts of iron, and in highfiring =
might
flux the claybody and cause it to over-vitrify unless content of other
fluxes is adjusted.
I believe this is what Curtis was saying. Is that right Curtis?
- Vince
Vince Pitelka on fri 18 apr 08
Ivor wrote:
"However, since you wish to take issue with me I accept your challenge. The
information I have about prepared stains is that they are based on mixtures
of various transitional metal oxides which have been heated to fusion to
give stable compounds, many of which have similar molecular structures to
the Spinel Group of Compounds. Typical characteristics of this group of
substances are their resistance to heat, showing no indication of fusion
under the action of the blowpipe, exceptional hardness of 8 on Mohs scale
and a high degree of chemical inertness ensuring permanent physical
attributes. Since these are single unique compounds, decomposition would be
necessary to release Iron oxide. Then, if the temperature was high enough
for a reaction between Ferrous Oxide and free silica the relatively low
melting point compound 2FeO.SiO2 might form and enhance vitrification. But
this would destroy the qualities of the stain."
That's not true, Ivor. Different stains are formulated with different
degrees of refractory properties. Except for the zirconium inclusion
stains, most stains from Mason and other North American manufacturers are
incorporated into the glassy melt at the intended maturation temperature.
Thus, any material inclined to act like a flux will do so once it is fused
into the glassy melt. That is the case with iron, and many dark brown and
black stains contain significant amounts of iron. In midrange and highfire
reduction firing, that iron will be available as a flux.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Ivor and Olive Lewis on sat 19 apr 08
Dear Vince Pitelka,=20
You invoke prior chemical reactions which are known to make many stains =
unstable and loose their ability to reproduce the intended colour.
See what Frank Hamer says under "Spinel"
I told you <<...these are single unique compounds, decomposition would =
be necessary to release Iron oxide. Then, if the temperature was high =
enough for a reaction between Ferrous Oxide and free silica the =
relatively low melting point compound 2FeO.SiO2 might form and enhance =
vitrification. But this would destroy the qualities of the stain>> You =
propose Reduction which is a chemical reaction So Please..What is =
untrue ?
Yours sincerely,
Ivor
Ivor Lewis.
Redhill,
South Australia.
Curtis Benzle on mon 21 apr 08
Thanks for the clarification Vince. "Flux"...... Best of luck to you and
Ivor.
Curt
On Wed, Apr 16, 2008 at 7:51 PM, Vince Pitelka wrote:
> Curtis Benzle wrote:
> "Also note that the higher the stain percentage of black you use the more
> the clay will vitrify. The stain is a catalyst."
>
> Ivor Lewis wrote:
> "This is an interesting idea. Given the common usage of the term
> "Catalyst"
> as a substance that promotes a faster rate of a chemical reaction without
> itself being changed in any way are you telling us that stains are not
> integrated or dissolved into the materials in which they are mixed?"
>
> Dear Ivor -
> In some cases, it is an advantage to listen to what a person meant rather
> than what they said. I understood exactly what Curtis meant, but I am not
> a
> chemist, and I doubt that he is either. You are a chemist, and you
> noticed
> the use of the word "catalyst, which I suppose was technically incorrect
> in
> that context. I understood that he meant "flux." The darker brown and
> black stains often contain large amounts of iron, and in highfiring might
> flux the claybody and cause it to over-vitrify unless content of other
> fluxes is adjusted.
>
> I believe this is what Curtis was saying. Is that right Curtis?
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net; wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka
>
>
> ______________________________________________________________________________
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, change your
> subscription settings or unsubscribe/leave the list here:
> http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots2@visi.com
>
Curtis Benzle on mon 21 apr 08
Hi Paulette:
From what I can remember from my early experimentations with my clay body
thirty + years ago
talc did have all of the ugly characteristics you describe. I switched over
to neph sye
and found it(it combination with a potash spar) do be much more agreeable.
I still could
never throw with my clay but I have other clays in the studio for that. My
clay(you can see
it at benzleporcelain.com) was meant only to focus on translucency and color
and it does both
pretty well.
I have been thinking back to the beginning of this conversation and at some
point it seems like
a concern for conservation or environment came up. In that context, I would
still encourage you to
lower your stain content as the stuff(stain) is expensive and packed with
the kind of natural material that is in relatively
short supply.
Good luck with you experimentations! (If you want to try neph sye I would
suggest around 25 % for starters
but fire it on a slab of soft brick in case it melts....
Curt
On Wed, Apr 16, 2008 at 9:26 PM, Paulette Carr
wrote:
> Curt,
>
> Thank you for the information. That is very encouraging. I was
> about to abandon testing the lower concentrations of black stain, but
> I will now included them to make certain that I am not adding more
> than I need for saturation. If I understand what you are saying with
> regard to higher percentages of black, the colored clay body will
> have a lower absorption with the colorant than without it. Talc
> bodies are "odd" in that, unlike other clay bodies they do not seem
> to decrease the absorption until they approach melting. I have found
> that this body maintains it's 10% absorption from ^04 - ^01, and then
> begins to deform around ^1. So, I have made the assumption that my
> pieces are "mature" when fired to ^03. Are you suggesting that the
> high percentages of black stain will cause the clay to deform at
> lower heatwork, or will it reduce the absorption without
> deformation? Perhaps, someone with technical knowledge of talc
> bodies will weigh in on the maturation/vitrification behavior of
> these clay bodies. I will keep the compatibility issue in mind.
>
> My best,
> Paulette
>
> Paulette Carr Studio
> St. Louis, MO
> Member, Potters Council
>
>
> Curtis Benzle wrote:
>
> A low fire talc body should yield a darker color when fired to
> maturity than a bisqued piece. It has to do with the vitrification
> and the talc body fired
> to maturity should be more vitreous. I have fired colored porcelain
> to cone 8 (for 30+ years) and the highest colorant percentage I use
> is 10% for Mason 6600 black. It yields a jet black(at maturity...).
> No matter what clay you use, if you fire it close to
> maturity you should be able to cut the stain percentage back to no
> more than 10 %.
>
> Vince's comments are dead on. Also note that the higher the stain
> percentage of black you use the more the clay will vitrify. The
> stain is a catalyst. This could mess up your compatibility if you are
> using the nerikomi technique.
>
>
>
> ______________________________________________________________________________
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, change your
> subscription settings or unsubscribe/leave the list here:
> http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots2@visi.com
>
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