Wyndham Dennison on wed 6 aug 08
>
> Date: Tue, 5 Aug 2008 12:46:53 +0200
> From: jean szostek
> Subject: Re: Firing the hell outta red
>
> hi jon,
> im firiing copper red and the experience tells me that the most beautifull
> reds are the reds with a
> frit in the recipe
> my recipe is very simpel : frit (high alkaline) 55 / whiting 15 / kaolin 30
> / copper oxide 0,5
> i fire this recipe in 8 H30 and heavy reduction from 8500 C until 11000 C ,
> than lighter reduction until the end, the cooling you can do experiments
> because it is very interesting
> greatings from belgium jean
> www.szostekjean.be
Jean those are great Copper reds. Some of the common elements I also
believe are a high alkaline glaze with calcium, the early reduction
because the glaze must reduce before the glaze melt and the backing off
of the reduction in the cone 5-6 range til finished, these are all
things you have listed. I also find that back pressure by way of the
damper holds the envelope of reduction inside the kiln (sorta like
keeping a soda bottle's fizz in the bottle) and keeps extraneous oxygen
from capturing the copper ions and leaving the surface bare of color.
If reduction is kept heavy for too long a period the glaze goes muddy
from carbon(my explanation), you have it nailed.
What is the final temp that you are firing to, It looks like a hard 11.
I think it's interesting that there is no Tin oxide in your glaze.
If I might mention something that works for me that might be of interest
to you and others is to calcine half the kaolin in the recipe. In my
applications, which tend to be thick, this helps me from having glaze
crawl and bare spots. If you have access to Glomax, this is a calcined
kaolin.There should still be enough natural clay(15%)+(15%glomax) to
keep the glaze in suspension
Thanks again for the link to some great reds, Wyndham
jean szostek on thu 7 aug 08
hi wyndham,
first about the tin : if you use tin you dont have transparency in de glaze,
and it becomes more dark red
it wonders me , that it becomes darker.
your idea about the calcined kaolin is maybe good, but if you cut the
fluidity of the glaze, the beautiful colors disapears,
on this mater im still experimenting - im only six years potter- so ill
still have to learn mutch
my next kiln i tough will try the calcined kaolin, maybe with different
amounts
i let you now, how it turns out
thank you for the advise jean
----- Original Message -----
From: "Wyndham Dennison"
To:
Sent: Wednesday, August 06, 2008 4:04 PM
Subject: Re: Copper Red, Red Hot
>
> Date: Tue, 5 Aug 2008 12:46:53 +0200
> From: jean szostek
> Subject: Re: Firing the hell outta red
>
> hi jon,
> im firiing copper red and the experience tells me that the most beautifull
> reds are the reds with a
> frit in the recipe
> my recipe is very simpel : frit (high alkaline) 55 / whiting 15 / kaolin
> 30
> / copper oxide 0,5
> i fire this recipe in 8 H30 and heavy reduction from 8500 C until 11000 C
> ,
> than lighter reduction until the end, the cooling you can do experiments
> because it is very interesting
> greatings from belgium jean
> www.szostekjean.be
Jean those are great Copper reds. Some of the common elements I also
believe are a high alkaline glaze with calcium, the early reduction
because the glaze must reduce before the glaze melt and the backing off
of the reduction in the cone 5-6 range til finished, these are all
things you have listed. I also find that back pressure by way of the
damper holds the envelope of reduction inside the kiln (sorta like
keeping a soda bottle's fizz in the bottle) and keeps extraneous oxygen
from capturing the copper ions and leaving the surface bare of color.
If reduction is kept heavy for too long a period the glaze goes muddy
from carbon(my explanation), you have it nailed.
What is the final temp that you are firing to, It looks like a hard 11.
I think it's interesting that there is no Tin oxide in your glaze.
If I might mention something that works for me that might be of interest
to you and others is to calcine half the kaolin in the recipe. In my
applications, which tend to be thick, this helps me from having glaze
crawl and bare spots. If you have access to Glomax, this is a calcined
kaolin.There should still be enough natural clay(15%)+(15%glomax) to
keep the glaze in suspension
Thanks again for the link to some great reds, Wyndham
No virus found in this incoming message.
Checked by AVG - http://www.avg.com
Version: 8.0.138 / Virus Database: 270.5.12/1595 - Release Date: 6/08/2008
8:23
Ivor and Olive Lewis on fri 8 aug 08
The best account I have read relating to the production of Copper Red
glazes was presented in "Handbook for Australian Potters" by Janet De
Boos, Stephen Harrison and Leonard Smith. ISBN 0-45400448-6.
In a section headed Colloidal Colour ( p 56 ) the natural history of
this glaze style is described. Chemical decomposition of the original
Copper compound as the kiln is heated under reducing condition leaves
a residue of finely divided elemental metallic copper distributed
throughout the glaze. Agglomeration of submicroscopic particles during
cooling leaves a colloidal suspension. The final colour depends upon
the size of these colloidal particles which cause interference with
refracted and reflected light passing through the transparent base
glaze.
I did a bead test recently. Using Borax, Copper (Black) oxide gave a
green colouration. Using a Boron Frit I was presented with an opaque
Red bead. Mo attempt was made to reduce the oxide.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Neon-Cat on fri 8 aug 08
Ivor, is the text ("Handbook for Australian Potters") from 1978 (30 years
ago)?
Were the authors theorizing? Or did they test, and if so using what was the
methodology (in brief)?
Thanks!
Marian
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG]On Behalf Of Ivor and Olive
Lewis
Sent: Friday, August 08, 2008 1:34 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Copper Red, Red Hot
The best account I have read relating to the production of Copper Red
glazes was presented in "Handbook for Australian Potters" by Janet De
Boos, Stephen Harrison and Leonard Smith. ISBN 0-45400448-6.
In a section headed Colloidal Colour ( p 56 ) the natural history of
this glaze style is described. Chemical decomposition of the original
Copper compound as the kiln is heated under reducing condition leaves
a residue of finely divided elemental metallic copper distributed
throughout the glaze. Agglomeration of submicroscopic particles during
cooling leaves a colloidal suspension. The final colour depends upon
the size of these colloidal particles which cause interference with
refracted and reflected light passing through the transparent base
glaze.
I did a bead test recently. Using Borax, Copper (Black) oxide gave a
green colouration. Using a Boron Frit I was presented with an opaque
Red bead. Mo attempt was made to reduce the oxide.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Ivor and Olive Lewis on sat 9 aug 08
Dear Marian,
Yes it is of that era.
Janet De Boos, one of the authors, is a graduate Chemist. I see no
reason to doubt information published in her name.
Weyl, who I mentioned recently, gives four pathways to reaching a
copper red.
I think the fascinating question to answer asks about the reasons both
Copper oxides seem to refuse to dissolve in a silicate melt and
precipitate pure Copper silicate on cooling. That Sodium oxide, and
Calcium oxide form silicates while cuprous and cupric oxides do not
seems rather curious.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Suchman ceramics on sat 9 aug 08
Just a quick note to say you got some dam nice reds goin' on there Jean!!
-einoside-
On Thu, Aug 7, 2008 at 1:24 AM, jean szostek wrote:
> hi wyndham,
> first about the tin : if you use tin you dont have transparency in de
> glaze,
> and it becomes more dark red
> it wonders me , that it becomes darker.
> your idea about the calcined kaolin is maybe good, but if you cut the
> fluidity of the glaze, the beautiful colors disapears,
> on this mater im still experimenting - im only six years potter- so ill
> still have to learn mutch
> my next kiln i tough will try the calcined kaolin, maybe with different
> amounts
> i let you now, how it turns out
> thank you for the advise jean
> ----- Original Message -----
> From: "Wyndham Dennison"
> To:
> Sent: Wednesday, August 06, 2008 4:04 PM
> Subject: Re: Copper Red, Red Hot
>
>
>
>> Date: Tue, 5 Aug 2008 12:46:53 +0200
>> From: jean szostek
>> Subject: Re: Firing the hell outta red
>>
>> hi jon,
>> im firiing copper red and the experience tells me that the most beautifull
>> reds are the reds with a
>> frit in the recipe
>> my recipe is very simpel : frit (high alkaline) 55 / whiting 15 / kaolin
>> 30
>> / copper oxide 0,5
>> i fire this recipe in 8 H30 and heavy reduction from 8500 C until 11000 C
>> ,
>> than lighter reduction until the end, the cooling you can do experiments
>> because it is very interesting
>> greatings from belgium jean
>> www.szostekjean.be
>>
> Jean those are great Copper reds. Some of the common elements I also
> believe are a high alkaline glaze with calcium, the early reduction
> because the glaze must reduce before the glaze melt and the backing off
> of the reduction in the cone 5-6 range til finished, these are all
> things you have listed. I also find that back pressure by way of the
> damper holds the envelope of reduction inside the kiln (sorta like
> keeping a soda bottle's fizz in the bottle) and keeps extraneous oxygen
> from capturing the copper ions and leaving the surface bare of color.
> If reduction is kept heavy for too long a period the glaze goes muddy
> from carbon(my explanation), you have it nailed.
> What is the final temp that you are firing to, It looks like a hard 11.
> I think it's interesting that there is no Tin oxide in your glaze.
> If I might mention something that works for me that might be of interest
> to you and others is to calcine half the kaolin in the recipe. In my
> applications, which tend to be thick, this helps me from having glaze
> crawl and bare spots. If you have access to Glomax, this is a calcined
> kaolin.There should still be enough natural clay(15%)+(15%glomax) to
> keep the glaze in suspension
> Thanks again for the link to some great reds, Wyndham
>
> No virus found in this incoming message.
> Checked by AVG - http://www.avg.com
> Version: 8.0.138 / Virus Database: 270.5.12/1595 - Release Date: 6/08/2008
> 8:23
>
--
pagan by nature
Neon-Cat on sat 9 aug 08
Ivor, I merely asked if the authors were theorizing or if they'd done tests
and which ones? It is a lovely glaze story as presented but seems somewhat
wanting so I was curious. I also wanted to know what ground they'd covered.
Lots of people study copper-silicon mixes for a variety of reasons in our
current era, just as they've done in the past.
Since you're always asking about silica and copper here's a good read:
Mechanism of Formation of Amorphous Silica Inclusion in Silicon Deoxidized
Copper, Kyoko Wasai and Kusuhiro Mukai, ISIJ International, Vol. 43 (2003),
No. 5, pp. 606-611
http://www.journalarchive.jst.go.jp/english/jnlabstract_en.php?cdjournal=isi
jinternational1989&cdvol=43&noissue=5&startpage=606
It has silica inclusions inside copper metal, a different way of looking at
things although not our norm here on clayart. The principles underlying this
copper-silica interaction are the same either way (silica in/copper out or
copper in/silica out). This is but one of many ways in which copper and
silica might interact in our copper glazes under kiln conditions. We need to
look to the S-OH- and S-H+ models for some of the answers to this
complicated copper-silica match-up, too. In the study (above link) the
silicon dioxide reduces the copper not kilns under reducing condition as
your authors stated. Under a reduction atmosphere in a kiln environment you
might also consider that SiO2 + 2CO <=> Si + 2CO2 in which the silicon
dioxide is reduced.
So, a little topsy-turvy but that's OK. Modern copper-silica investigations
are bringing to light all kinds of interesting explanations for how things
work. This article speaks to part of the answer and gives a sense of just
what might be required for correct theories to emerge.
And every text out there, no matter where color is being defined for a
material allows for a particle-size and refracted/reflected light
correlation as light passes through a substance. I wanted to know how your
authors identified (if they did) which species of copper they were "seeing"
in the glaze melt. Copper oxides so easily reduce and copper so easily
oxidizes or re-oxidizes. How do you know that we potters are not forming
copper silicates in our glazes? Even your authors refer to "colloidal
particles " (as paraphrased and posted by you), could they mean a copper
silicate of some sort? Part of the problem of conceptually understanding the
questions at hand deal with the types of reaction mechanisms we
potter-chemists come to expect and the terminology we wish to use. Copper
and silicon are not quite straightforward enough to be covered by rudimental
general chemistry. So we all go a little deeper in our understanding and
keep an open mind as copper-silica interactions become clearer to us.
Happy reading,
Marian
www.neon-cat.com
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG]On Behalf Of Ivor and Olive
Lewis
Sent: Saturday, August 09, 2008 1:14 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Copper Red, Red Hot
Dear Marian,
Yes it is of that era.
Janet De Boos, one of the authors, is a graduate Chemist. I see no
reason to doubt information published in her name.
Weyl, who I mentioned recently, gives four pathways to reaching a
copper red.
I think the fascinating question to answer asks about the reasons both
Copper oxides seem to refuse to dissolve in a silicate melt and
precipitate pure Copper silicate on cooling. That Sodium oxide, and
Calcium oxide form silicates while cuprous and cupric oxides do not
seems rather curious.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Ivor and Olive Lewis on sun 10 aug 08
Dear Marian,
I will have a look at that site though it sounds as though this is a
metallurgical text.
Deoxidised
Copper,>
But reading between the lines it sounds as though the people doing
this research did not identify a binary compound of Copper oxide and
Silicon dioxide. Elemental Silicon is frequently used as a deoxidising
agent in metallurgical reactions during refining. The metalloid is
extracted from Quartz by reduction with Carbon a under the influence
of the electric arc with temp of about 4000 deg C.
You must realise that I accept what most authors have to say,
especially if they give me some reasonable references and have
adequate qualifications. If I have doubts I try to use my own
resources to see what happens. Frank Hamer tells us the brightest reds
are due to colloidal copper. Did he determine that for himself by
experiment or did he use information from Parmellee ? Speculating on
how authors reach their verdicts leads nowhere.
As far as I know the Group 1B elements are predominantly associated as
native metals in Quartz rocks state.
Thanks for your interest.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Ivor and Olive Lewis on sun 10 aug 08
Dear Wyndham Dennison,
Sorry but I have no answer for you. The best way to find out about
potential reactions is to construct potential equations then calculate
heats of formation. Your results would tell you if your proposals are
possible or improbable.
Regarding layered red copper glazes, it is my understanding that the
upper surface layer seals the surface and protects the reduced copper
oxide from reoxidation during cooling. I can see that this would help
to avoid dual coloured pots where the side exposed to a current of
cooling air changes to green while the side that is protected and must
remain warmer becomes red.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Neon-Cat on mon 11 aug 08
Ivor, it's fun exploring a bit of clay & glaze-related chemistry with you.
With me, things might get a little strange so I hope you'll flow along. You
do like a touch of strange, right?
I haven't had time yet to check out the many copper-silicon minerals and see
how they have come together. Clearly you did not think much of the cooper
vermiculite example we chatted briefly about. But it speaks to the nature of
both copper and silicon - they can be strange, too, and not always perfect
fits according to those standard Group 1B (copper) and Group 4A (silicon)
periodic table characteristics drawn up so very many years ago.
Would you take a copper-silicate in combination with another element? Like
barium maybe? There's a cyclic barium copper silicate, Ba2Cu2[Si4O12],
identified in the lovely blue glaze on Chinese painted ceramic objects
attributed to the Han dynasty (208 BC-220 AD) and found to be present in
octagonal sticks from the Warring States period (475-221 BC) and the Han
dynasty. Now how did that happen? And so it goes in the glaze melt.
Chemistry is precise. Fundamental reaction mechanisms will not change across
the years or in differing fields of applications so much of what folks are
discovering in metallurgy and elsewhere is totally applicable to our glaze
chemistry.
Keep on making me think - a gal could do worse ...
Cheers!
Marian
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG]On Behalf Of Ivor and Olive
Lewis
Sent: Sunday, August 10, 2008 1:52 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Copper Red, Red Hot
Dear Marian,
I will have a look at that site though it sounds as though this is a
metallurgical text.
Deoxidised
Copper,>
But reading between the lines it sounds as though the people doing
this research did not identify a binary compound of Copper oxide and
Silicon dioxide. Elemental Silicon is frequently used as a deoxidising
agent in metallurgical reactions during refining. The metalloid is
extracted from Quartz by reduction with Carbon a under the influence
of the electric arc with temp of about 4000 deg C.
You must realise that I accept what most authors have to say,
especially if they give me some reasonable references and have
adequate qualifications. If I have doubts I try to use my own
resources to see what happens. Frank Hamer tells us the brightest reds
are due to colloidal copper. Did he determine that for himself by
experiment or did he use information from Parmellee ? Speculating on
how authors reach their verdicts leads nowhere.
As far as I know the Group 1B elements are predominantly associated as
native metals in Quartz rocks state.
Thanks for your interest.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
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