Michael Banks on sat 13 nov 99
Hi Paul,
Yes, I agree, high calcium gloss glazes seem OK and work best for Cr-Sn
crimsons too. The quote below comes from Cerdec and it is unclear what they
mean by "excessive". Fairly loose term. Actually, for the limit formulae
that I use, 0.7 mol props CaO is not over the top for cone 6 and can reach
0.8 at cone 9-10. I stick to my previous comment that Cerdec probably mean
flux-saturation glazes in the sense that Robin Hopper uses the term, i.e:
extremely fluxed glazes. As for zinc, I was noting that Cerdec say that
their cadmium inclusion stains are compatible with this flux. Chrome-tin
stains are not of course.
Michael
>>(Quote): "Note that
> > excessive amounts of barium, boron, calcium, magnesium, tin oxide and
other
> > alkalis can cause the color to take on a browner, grayer, more violet or
> > more washed-out appearance." (Unquote).
> >
> > They seem to be saying here that flux-saturation glazes are out.
>
Paul Lewing wrote:
> Now this is really interesting. I have always heard that to get the
> brightest colors from these stains, you need a glaze high in calcium.
> And in my experience, this has proven true. The best base glaze I've
> found for them is Tony Hansen's 5x20 glaze, which has more calcium than
> any other recipe I have, about .70 molecular equivalents. The upper
> limit according to teh limit formulas I use should be .6. So I don't
> know about safe, but I know about color.
> I have also tried them in a base I developed that has gobs of barium and
> boron, and they're not as bright. They are indeed grayer and more
> violet. I've never tried them with tin, but I'd assume that would make
> the color paler. I've also never tried them in a high zinc base, but if
> you tell me that won't work, I'll for sure try it.
> Paul Lewing, Seattle
>
Paul Lewing on tue 16 nov 99
Michael,
thanks for the validation about what I've observed about cadmium being a
brighter red in high-calcium glazes. Now I have another question about
using these things.
All the glazes I've used them successfully in have resulted in a bright
but very flat color- no crystalization or streaking- no "action". I'd
prefer a little more visual texture here, as what I'm using them for is
part of painting my glazed landscapes, and want to use them for fall
foliage.
I've tried adding other colorants to modify the harsh red color, but
everything I've tried so far has killed the brightness. Iron especially
seems to do this. I got a bright red with good-sized black spots by
ading granular manganese, which was interesting, but not exactly what I
was lookig for. My last test was using a coarse iron-bearing brick clay
as a substitute for EPK in Tony Hansen's 5x20 glaze. That's equal parts
Custer, frit 3134, wollastonite, EPK and silica, and is the glaze that
makes these stains the brightest of any glaze I've tried so far (at cone
4 in oxidation). It came out looking like a chrome-tin pink.
So now I'm thinking for my next series of adding granular rutile, maybe
ilmenite, or modifying the base recipe by substituting the EPK with a
clay that doesn't have quite so much iron, like a slip I have from
Montana, or Ravenscrag Slip. Or maybe adding some wood ash or some
volcanic ash. I think I'll also try just raising the Si:Al ratio.
Has anybody tried any of these things, or can you think of anything else
I could try?
Thanks, Paul Lewing, Seattle
Michael Banks on wed 17 nov 99
Paul Lewing wrote----------------------------
> All the glazes I've used them successfully in have resulted in a bright
> but very flat color- no crystalization or streaking- no "action". I'd
> prefer a little more visual texture here, as what I'm using them for is
> part of painting my glazed landscapes, and want to use them for fall
> foliage.
Wood ash (being a rich source of alkalis) might dissolve the zircon base,
weakening the colour (quite apart from releasing Cd fume). Rutile adds
iron, which you have already established dulls the red.
Try white titanium dioxide in increments, e.g. 2,4,6,8,10% etc.
Michael Banks,
Nelson,
New Zealand
John K Dellow on wed 17 nov 99
Paul ,
when I worked for Vladimir Tichy in his studio in the late
70's , he used a lot cadmium/celemium ,red,yellow & orange blazes
on terra-cotta .
Before glazing ,the bisque was dipped in a wash of manganese &
copper to darken the body ( his words ) . also he highlighted
each with the other . I.E. orange & yellow wiped over red in
patches.
Hope this helps.
John dellow
Paul Lewing wrote:
>
> ----------------------------Original message----------------------------
> Michael,
> thanks for the validation about what I've observed about cadmium being a
> brighter red in high-calcium glazes. Now I have another question about
> using these things.
> All the glazes I've used them successfully in have resulted in a bright
> but very flat color- no crystalization or streaking- no "action". I'd
> prefer a little more visual texture here, as what I'm using them for is
> part of painting my glazed landscapes, and want to use them for fall
> foliage.
> I've tried adding other colorants to modify the harsh red color, but
> everything I've tried so far has killed the brightness. Iron especially
> seems to do this. I got a bright red with good-sized black spots by
> ading granular manganese, which was interesting, but not exactly what I
> was lookig for. My last test was using a coarse iron-bearing brick clay
> as a substitute for EPK in Tony Hansen's 5x20 glaze. That's equal parts
> Custer, frit 3134, wollastonite, EPK and silica, and is the glaze that
> makes these stains the brightest of any glaze I've tried so far (at cone
> 4 in oxidation). It came out looking like a chrome-tin pink.
> So now I'm thinking for my next series of adding granular rutile, maybe
> ilmenite, or modifying the base recipe by substituting the EPK with a
> clay that doesn't have quite so much iron, like a slip I have from
> Montana, or Ravenscrag Slip. Or maybe adding some wood ash or some
> volcanic ash. I think I'll also try just raising the Si:Al ratio.
> Has anybody tried any of these things, or can you think of anything else
> I could try?
> Thanks, Paul Lewing, Seattle
--
John Dellow "the flower pot man"
Home Page http://www.welcome.to/jkdellow
gambaru on wed 17 nov 99
Paul:One Maybe: try small percentage of iron chromate as it doesn't really
blend in completely and a dusting effect results (brushed on) Marj
----- Original Message -----
From: Paul Lewing
To:
Sent: Tuesday, November 16, 1999 12:14 PM
Subject: Re: Keeping the cadmium colourful
> ----------------------------Original message----------------------------
> Michael,
> thanks for the validation about what I've observed about cadmium being a
> brighter red in high-calcium glazes. Now I have another question about
> using these things.
> All the glazes I've used them successfully in have resulted in a bright
> but very flat color- no crystalization or streaking- no "action". I'd
> prefer a little more visual texture here, as what I'm using them for is
> part of painting my glazed landscapes, and want to use them for fall
> foliage.
> I've tried adding other colorants to modify the harsh red color, but
> everything I've tried so far has killed the brightness. Iron especially
> seems to do this. I got a bright red with good-sized black spots by
> ading granular manganese, which was interesting, but not exactly what I
> was lookig for. My last test was using a coarse iron-bearing brick clay
> as a substitute for EPK in Tony Hansen's 5x20 glaze. That's equal parts
> Custer, frit 3134, wollastonite, EPK and silica, and is the glaze that
> makes these stains the brightest of any glaze I've tried so far (at cone
> 4 in oxidation). It came out looking like a chrome-tin pink.
> So now I'm thinking for my next series of adding granular rutile, maybe
> ilmenite, or modifying the base recipe by substituting the EPK with a
> clay that doesn't have quite so much iron, like a slip I have from
> Montana, or Ravenscrag Slip. Or maybe adding some wood ash or some
> volcanic ash. I think I'll also try just raising the Si:Al ratio.
> Has anybody tried any of these things, or can you think of anything else
> I could try?
> Thanks, Paul Lewing, Seattle
>
David Hendley on thu 18 nov 99
Include Titanium dioxide in the recipe along with the
stain.
I've not done this with cadmium stains since I use them
only in slips, not glazes,
but I add titanium to my glazes colored with 'regular' stains.
It adds texture and interest to glazes that are too flat
and uniform for my tastes, without affecting the color.
4% titanium dioxide works for me.
--
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com/
----- Original Message -----
From: Paul Lewing
To:
Sent: Tuesday, November 16, 1999 11:14 AM
Subject: Re: Keeping the cadmium colourful
| ----------------------------Original message----------------------------
| Michael,
| thanks for the validation about what I've observed about cadmium being a
| brighter red in high-calcium glazes. Now I have another question about
| using these things.
| All the glazes I've used them successfully in have resulted in a bright
| but very flat color- no crystalization or streaking- no "action". I'd
| prefer a little more visual texture here, as what I'm using them for is
| part of painting my glazed landscapes, and want to use them for fall
| foliage.
| I've tried adding other colorants to modify the harsh red color, but
| everything I've tried so far has killed the brightness. Iron especially
| seems to do this. I got a bright red with good-sized black spots by
| ading granular manganese, which was interesting, but not exactly what I
| was lookig for. My last test was using a coarse iron-bearing brick clay
| as a substitute for EPK in Tony Hansen's 5x20 glaze. That's equal parts
| Custer, frit 3134, wollastonite, EPK and silica, and is the glaze that
| makes these stains the brightest of any glaze I've tried so far (at cone
| 4 in oxidation). It came out looking like a chrome-tin pink.
| So now I'm thinking for my next series of adding granular rutile, maybe
| ilmenite, or modifying the base recipe by substituting the EPK with a
| clay that doesn't have quite so much iron, like a slip I have from
| Montana, or Ravenscrag Slip. Or maybe adding some wood ash or some
| volcanic ash. I think I'll also try just raising the Si:Al ratio.
| Has anybody tried any of these things, or can you think of anything else
| I could try?
| Thanks, Paul Lewing, Seattle
Hank Ray on fri 19 nov 99
The other day i glazed a bowl with an ash glaze, then dipped the rim in my
yellow glaze. After being fired to cone 10 the yellow was for the most part
gone, so i would think that ash is hard on the inclusion stains....
pete in okc ok
Earl Brunner on sat 20 nov 99
I decorated the outside of some oil lamps with both the orange and yellow
stains, glazed them with a good clear and sprinkled some ash on them before
firing. Where the ash was (and this held true for almost all of the different
colorants that I decorated with) the ash obliterated almost all brushwork, just
desolved it away. I have to think/suspect that the inclusion stains were toast
(so to speak). The color is gone in the area of the ash.
Hank Ray wrote:
> ----------------------------Original message----------------------------
> The other day i glazed a bowl with an ash glaze, then dipped the rim in my
> yellow glaze. After being fired to cone 10 the yellow was for the most part
> gone, so i would think that ash is hard on the inclusion stains....
>
> pete in okc ok
--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec@anv.net
Michael Banks on sun 21 nov 99
These two posts (copied below) sound like fairly good empirical evidence
that zircon encapsulated cadmium stains are dissolved and dispersed (with
the Cd probably going into the atmosphere) by high glaze alkali contents.
Any ceramic science students willing to do research on this one?
Michael Banks,
Nelson, New Zealand
Earl Brunner wrote:
> ----------------------------Original message----------------------------
> I decorated the outside of some oil lamps with both the orange and yellow
> stains, glazed them with a good clear and sprinkled some ash on them
before
> firing. Where the ash was (and this held true for almost all of the
different
> colorants that I decorated with) the ash obliterated almost all
brushwork, just
> desolved it away. I have to think/suspect that the inclusion stains were
toast
> (so to speak). The color is gone in the area of the ash.
>
> Hank Ray wrote:
>
> > ----------------------------Original message----------------------------
> > The other day i glazed a bowl with an ash glaze, then dipped the rim
in my
> > yellow glaze. After being fired to cone 10 the yellow was for the most
part
> > gone, so i would think that ash is hard on the inclusion stains....
> >
> > pete in okc ok
Paulette Carr on mon 22 nov 99
Michael,
I see a different result. I first laid down an ash slip glaze containing
approx. 5% carefully washed ash. I then painted over it with slip glazes
containing Cerdic Bordeaux and Cerdic Yellow, both cadmium inclusion
pigments. In both cases (cone 9 oxidation) the ash slip glaze broke through
the upper slip glaze as it does with all my slip glazes, but the red and
yellowish colors remained, albeit altered by the ash glaze, yielding very
attractive surfaces. Maybe the colors are retained in my work since my ash
is no longer highly alkali, as you suggested. But maybe it is also due to
the difference in glazes used and firing.
Paulette Carr
St. Louis, MO
Michael Banks wrote:
>----------------------------Original message----------------------------
>These two posts (copied below) sound like fairly good empirical evidence
>that zircon encapsulated cadmium stains are dissolved and dispersed (with
>the Cd probably going into the atmosphere) by high glaze alkali contents.
Earl Brunner wrote:
> ----------------------------Original message----------------------------
> I decorated the outside of some oil lamps with both the orange and yellow
> stains, glazed them with a good clear and sprinkled some ash on them
before
> firing. Where the ash was (and this held true for almost all of the
different
> colorants that I decorated with) the ash obliterated almost all
brushwork, just
> desolved it away. I have to think/suspect that the inclusion stains were
toast
> (so to speak). The color is gone in the area of the ash.
>
> Hank Ray wrote:
>
> > ----------------------------Original message----------------------------
> > The other day i glazed a bowl with an ash glaze, then dipped the rim
in my
> > yellow glaze. After being fired to cone 10 the yellow was for the most
part
> > gone, so i would think that ash is hard on the inclusion stains....
> >
> > pete in okc ok
| |
|
