Craig Martell on fri 13 oct 06
Hello Chun enthusiasts:
I don't know what the problem is or was with Sarah's chun but most of the
possible causes for a "non-chun" effect have been covered along with some
explanations of how Chuns work. It's also possible that this just is not a
well formulated chun. We cant' know because the recipe is unavailable.
Since the chun blue effect is a "light scattering" phenomena glaze
application is a big factor. I've tested and actually formulated some
chuns and I usually do several tests with graduating glaze thicknesses. If
chuns aren't applied thick enough the blue does not happen. The different
thicknesses on my test tiles showed this was the case with all of the chuns
I've worked with.
There are some very good explanations of Chun/Jun glazes that are in
print. Two that are fairly easy to acquire are "Stoneware Glazes A
Systematic Approach by Ian Currie and "Chinese Glazes" by Nigel
Wood. Chuns are fairly complex and both books shed some light on the chun
blue thing. They talk about light refraction from undisolved particles of
a specific size, phase separation, and the differing effects from the
silica and phosphorous glass formers.
I've been working on Chuns and Blue Celadons for quite a few years and
sometimes I wonder why I'm doing this. The Iron Blue glazes are very nice
but from my experience are hard to sell. I've worked with two types of
Blue Celadons. The first are the high potassium celadons which make a very
nice sky blue. Then I decided to see what other bases would encourage an
iron blue celadon and I worked on some Yingqing Celadons. I took a
percentage analysis from Nigel Wood's book and converted it to Gringo
materials available here in Gringoland(USA). The Yingqings are very nice
blues and differ from the potash iron blues in that the Yingqings are high
limestone glazes with sodium doing most of the auxiliary work The Blue
Celadons are different from Chun with respect to how the blue forms. The
Celadons are solution/pigment colored glazes whereas Chuns are blue from an
optical effect. As to which type is better, all I can say is: "who
knows?" I'll keep working on them no matter what the market tells me.
regards, Craig Martell Hopewell, Oregon
Janine Roubik on sat 14 oct 06
Hello,=0AThanks for the recipes. I'm excited to test them out , probably w=
ithin a week or two. So the second one I can swing, but in the first one (=
the David Fry), I don't know what "mudgee" limestone, "clay ceram", or "mdl=
" dolomite is. Would American whiting, EPK and dolomite work?=0AI'll try t=
o look up those chems. tomorrow...=0AThanks again. I'll try to post photos=
of them when I get a chance.=0AJanine =0A=0A=0A----- Original Message ----=
=0AFrom: Des & Jan Howard =0ATo: CLAYART@LSV.CERAMICS.=
ORG=0ASent: Saturday, October 14, 2006 4:48:28 PM=0ASubject: Re: Chun Glaze=
s and other iron blues=0A=0A=0AJanine=0AThe glaze you posted looks like a o=
xidation faux Jun.=0ATry these:=0ADavid Fry Jun (sorta!)=0Apotash feldspar =
45=0Asilica 25=0Amudgee limestone 17=0Aclay ceram =
9=0Abone ash 2=0Amdl dolomite 2=0A+ red iron oxide 1=
=0A=0ATichane Jun=0Apotash feldspar 48=0Asilica 31=0Alimeston=
e 20=0Abone ash 1=0A+ red iron oxide 1=0A=0ATry both of the=
se at Orton C10 1/2 - 11 1/2 Reduction=0AThe Fry will be bluer & more mobil=
e, the Tichane will be more satin.=0ASo, line blend the two of them to suit=
your kiln/cycle.=0ADes
Des & Jan Howard on sat 14 oct 06
Craig
I think the basic problem was nailed when Sarah posted that the
pots were fired in an electric kiln, soooo, unless the firer is doing
some electric reduction the glaze was oxidised, not the way to get a Jun.
Craig Martell wrote:
> I don't know what the problem is or was with Sarah's chun but most of the
> possible causes for a "non-chun" effect have been covered along with some
> explanations of how Chuns work. It's also possible that this just is
> not a
> well formulated chun. We cant' know because the recipe is unavailable.
>
I happily & heartily agree, remember Casson's "some & some", some for
the market,
& some for yourself.
Des
> I'll keep working on them no matter what the market tells me.
--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
http://www.luepottery.hwy.com.au
Janine Roubik on sat 14 oct 06
Hello Craig,=0ADo you have any recipes you'd be willing to share? I only h=
ave the one in John's book and I found this one somewhere...=0ABLUE CHUN GL=
AZE c/9-10=0A4210 G-200 Feld.=0A180 EPK=0A2720 Flint=0A900 Whiting=0A880 =
Dolomite=0A170 Zinc oxide=0A260 Tin Oxide=0A---------=0A10,200=0Aplus 400=
Rutile=0A 50 copper carbonate=0A=0ADoes that sound wierd to any=
one? There's no iron in it. I havn't had time to test either yet, just wo=
ndering....=0AThank you Gringo Chun master : )=0AJanine=0A=0A----- Original=
Message ----=0AFrom: Craig Martell =0ATo: CLAYART@LSV.CE=
RAMICS.ORG=0ASent: Friday, October 13, 2006 11:30:53 PM=0ASubject: Chun Gla=
zes and other iron blues=0A=0A=0AHello Chun enthusiasts:=0A=0AI don't know =
what the problem is or was with Sarah's chun but most of the=0Apossible cau=
ses for a "non-chun" effect have been covered along with some=0Aexplanation=
s of how Chuns work. It's also possible that this just is not a=0Awell for=
mulated chun. We cant' know because the recipe is unavailable.=0A=0ASince =
the chun blue effect is a "light scattering" phenomena glaze=0Aapplication =
is a big factor. I've tested and actually formulated some=0Achuns and I us=
ually do several tests with graduating glaze thicknesses. If=0Achuns aren'=
t applied thick enough the blue does not happen. The different=0Athickness=
es on my test tiles showed this was the case with all of the chuns=0AI've w=
orked with.=0A=0AThere are some very good explanations of Chun/Jun glazes t=
hat are in=0Aprint. Two that are fairly easy to acquire are "Stoneware Gla=
zes A=0ASystematic Approach by Ian Currie and "Chinese Glazes" by Nigel=0AW=
ood. Chuns are fairly complex and both books shed some light on the chun=
=0Ablue thing. They talk about light refraction from undisolved particles =
of=0Aa specific size, phase separation, and the differing effects from the=
=0Asilica and phosphorous glass formers.=0A=0AI've been working on Chuns an=
d Blue Celadons for quite a few years and=0Asometimes I wonder why I'm doin=
g this. The Iron Blue glazes are very nice=0Abut from my experience are ha=
rd to sell. I've worked with two types of=0ABlue Celadons. The first are =
the high potassium celadons which make a very=0Anice sky blue. Then I deci=
ded to see what other bases would encourage an=0Airon blue celadon and I wo=
rked on some Yingqing Celadons. I took a=0Apercentage analysis from Nigel =
Wood's book and converted it to Gringo=0Amaterials available here in Gringo=
land(USA). The Yingqings are very nice=0Ablues and differ from the potash =
iron blues in that the Yingqings are high=0Alimestone glazes with sodium do=
ing most of the auxiliary work The Blue=0ACeladons are different from Chun=
with respect to how the blue forms. The=0ACeladons are solution/pigment c=
olored glazes whereas Chuns are blue from an=0Aoptical effect. As to which=
type is better, all I can say is: "who=0Aknows?" I'll keep working on the=
m no matter what the market tells me.=0A=0Aregards, Craig Martell Hopewell=
, Oregon=0A=0A_____________________________________________________________=
_________________=0ASend postings to clayart@lsv.ceramics.org=0A=0AYou may =
look at the archives for the list or change your subscription=0Asettings fr=
om http://www.ceramics.org/clayart/=0A=0AModerator of the list is Mel Jacob=
son who may be reached at melpots@pclink.com.
John Britt on sat 14 oct 06
Janine,
Looks like it might be might be a copper blue - which means it is fired in
oxidation. In that recipe, you are getting iron from the rutile as well as
titanium and with the copper, it probably makes for a varigated milky blue
surface.
I have never tried it but it looks promising.
P.S. Do not read further unless you are a member of the Glaze Free-Trade
Society. Keep this super secret!! If you are not in the Glaze Free-Trade
Society you must go to the Archives and spend at least a week looking up
Chun Blue. You especially can't read this if you are a encrusted pain in
the ass clayarter who bitches and moans all day about the rules.
On page 95 of my book, I show a tile in the upper right corner, with
Jeff's Red fired in oxidation on a high iron body! It is a fantastic
tidbit that I put in there and probably remains unnoticed, since most
potters don't actually read, they only look at pictures. It is not
technically a chun blue but it sure is close to the look and very
beautiful! I fired it in a gas and wood kiln with similar results. Try it
in your electric and let use know. But put a warning so only the Glaze
Free-Trade Society members can read it.
Hope it helps all the newbies,
John Britt
www.johnbrittpottery.com
John Britt on sat 14 oct 06
I forgot to mention that if you add titanium dioxide to a copper red glaze
it will turn it blue even in reduction. I have some tiles on page 93 of
my book which demonstrate that very vividly.
This may explain why that glaze is labeled Blue Chun. (The 4 percent
rutile may provide enough titanium to "push" it toward blue.)
Hope it helps,
John Britt
www.johnbrittpottery.com
Janine Roubik on sun 15 oct 06
Hey John,=0AHa ha! Don't take this the wrong way (I don't need your partne=
r beating me up...) but I love you! And I love all my new clayart friends =
who make me laugh and teach me things.=0AYes, I would very much like to be =
a member of the Glaze Free-Trade Society. =0AYou should team up with the "S=
chool for Wayward Potters" lady and make t-shirts. The cool kids on the bl=
ock will covet them!! Britney Spears and Paris Hilton will buy them!!!=0A =
=0AWell, on that recipe I posted there is a footnote. I found it accidenta=
lly while I was searching for carbon-trap recipes. I am quoting here... "C=
hun glaze is an ancient and traditional Chinese glaze. It is not usually v=
ery blue. Traditionally blue in a Chun is caused by the reduction of rutil=
e, which can be chancy. Expect a creamy glaze that spreads into se=
veral visual layers. You might get hints of lavender as well as blue." En=
d quote.=0ASo that "reduction of rutile" part goes contrary to everything I=
've been hearing. Could it be that there might be a different "type" of Ch=
un, OR is this something that frequently gets accidentally labeled as Chun,=
OR was this person just full of the poop? I'm going to test it anyhow, i=
n reduction, just to see.=0A =0AI did see page 95, and I DID read it! Yeaa=
aa! : ) But, yes, I did just look at the pretty pictures the first 3 or 4=
times through the book!=0ASo when you tried it in the wood and gas kilns, =
what was the atmosphere like? =0AMy little dinosaur electric kiln I only u=
se for bisuqing, and I gas fire outside of my home. BUT.... I was talking =
with someone who wanted to try some oil spots and other oxidation/neutral g=
lazes, so if that comes to fruition, I'll pop a test of it in there. Do yo=
u think oil spots and fake chuns and Kakis would work if they were in a fir=
ing cycle designed for crystallines? Or would the prolonged soaks and cool=
ing mess with them somehow or make me spend hours cleaning kiln shelves? (N=
oooooo!!)=0A =0AThanks for pointing out the titanium in the flambes as a so=
urce of blue. Something more to think about! =0A=0AAnd, Off Topic, I pers=
onally would like to not use the word "newbie" anymore. It reminds me of H=
igh School. I was a dork and was in some senior classes when I was a fresh=
man. (I don't know what hapened to my intellect since then - oh wait I do =
- mothers, tell you children not to follow the Dead or hang out with guys i=
n bands who look like Robert Smith... ; ) ) They would chide "Hey freshm=
an....hey freshie.. freshie, fresh, freshie..." and throw spit balls at me.=
All-American jocks and cheerleaders they were, the future of our nation. =
Yes, I could have easily told them that I was much smarter than they were, =
but I was also smart enought to know that that would result in a punch to t=
he head. =0ASo long, really uneccessary story short, that's why the word n=
ewbie is like fingernails on a chalkboard to me. =0A =0AThanks, John, (and=
anyone else who cares) for all your help!! =0A =0ASorry for the long, wind=
ing goofiness of this reply - it was a long night at work. And I'm just a =
goof in general.=0A =0AJanine=0A=0A=0A =0A----- Original Message ----=0AFro=
m: John Britt =0ATo: CLAYART@LSV.CERAMICS.ORG=0ASent: Sa=
turday, October 14, 2006 6:26:48 PM=0ASubject: Re: Chun Glazes and other ir=
on blues=0A=0A=0AJanine,=0A=0ALooks like it might be might be a copper blue=
- which means it is fired in=0Aoxidation. In that recipe, you are getting =
iron from the rutile as well as=0Atitanium and with the copper, it probably=
makes for a varigated milky blue=0Asurface.=0A=0AI have never tried it but=
it looks promising.=0A=0AP.S. Do not read further unless you are a member =
of the Glaze Free-Trade=0ASociety. Keep this super secret!! If you are not=
in the Glaze Free-Trade=0ASociety you must go to the Archives and spend at=
least a week looking up=0AChun Blue. You especially can't read this if yo=
u are a encrusted pain in=0Athe ass clayarter who bitches and moans all day=
about the rules.=0A=0AOn page 95 of my book, I show a tile in the upper ri=
ght corner, with=0AJeff's Red fired in oxidation on a high iron body! It is=
a fantastic=0Atidbit that I put in there and probably remains unnoticed, s=
ince most=0Apotters don't actually read, they only look at pictures. It is=
not=0Atechnically a chun blue but it sure is close to the look and very=0A=
beautiful! I fired it in a gas and wood kiln with similar results. Try it=
=0Ain your electric and let use know. But put a warning so only the Glaze=
=0AFree-Trade Society members can read it.=0A=0AHope it helps all the newbi=
es,=0A=0AJohn Britt=0Awww.johnbrittpottery.com=0A=0A_______________________=
_______________________________________________________=0ASend postings to =
clayart@lsv.ceramics.org=0A=0AYou may look at the archives for the list or =
change your subscription=0Asettings from http://www.ceramics.org/clayart/=
=0A=0AModerator of the list is Mel Jacobson who may be reached at melpots@p=
clink.com.
Des & Jan Howard on sun 15 oct 06
Janine
Sorry about the use of my local materials, up early this a.m.,
brekky at the keyboard, got my Clayart fix, then off.
Just read it as:
David Fry Jun (sorta!)
potash feldspar 45
silica 25
limestone 17
kaolin 9
bone ash 2
dolomite 2
+ red iron oxide 1
Despite some people's handwringing I don't think it matters
much a damn what you use. It is a test after all, materials/kilns/cycles
all affect the results. I look forward to seeing your photos.
Des
Janine Roubik wrote:
>Thanks for the recipes. I'm excited to test them out , probably within a week or two. So the second one I can swing, but in the first one (the David Fry), I don't know what "mudgee" limestone, "clay ceram", or "mdl" dolomite is. Would American whiting, EPK and dolomite work?
>I'll try to look up those chems. tomorrow...
>Thanks again. I'll try to post photos of them when I get a chance.
>
>
--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
http://www.luepottery.hwy.com.au
Craig Martell on sun 15 oct 06
Des was saying:
>I think the basic problem was nailed when Sarah posted that the
>pots were fired in an electric kiln, soooo, unless the firer is doing
>some electric reduction the glaze was oxidised, not the way to get a Jun.
Hello Des:
Oh, I missed that part of the discussion. Yes, that would be a problem
with the chun blue.
I was talking with Ian Currie some time back and he was thinking that
oxidation chuns might be possible with the addition of some zinc oxide. I
don't remember all the details that we mulled over but I can ask him again
and see what the plan would be to pursue an oxidized chun.
regards, Craig Martell Hopewell, Oregon
Lee Love on sun 15 oct 06
On 10/14/06, Des & Jan Howard wrote:
> Craig
> I think the basic problem was nailed when Sarah posted that the
> pots were fired in an electric kiln, soooo, unless the firer is doing
> some electric reduction the glaze was oxidised, not the way to get a Jun.
My chun likes heavy reduction. Thick, on a white clay body. 4%
copper slip on body before bisque will give you copper red. As
will copper glazes like seiji nuka on top of the chun.
--
Lee in Mashiko, Japan
http://potters.blogspot.com/
"Let the beauty we love be what we do." - Rumi
"When we all do better. We ALL do better." -Paul Wellstone
Des & Jan Howard on sun 15 oct 06
Janine
The glaze you posted looks like a oxidation faux Jun.
Try these:
David Fry Jun (sorta!)
potash feldspar 45
silica 25
mudgee limestone 17
clay ceram 9
bone ash 2
mdl dolomite 2
+ red iron oxide 1
Tichane Jun
potash feldspar 48
silica 31
limestone 20
bone ash 1
+ red iron oxide 1
Try both of these at Orton C10 1/2 - 11 1/2 Reduction
The Fry will be bluer & more mobile, the Tichane will be more satin.
So, line blend the two of them to suit your kiln/cycle.
Des
Janine Roubik wrote:
>Hello Craig,
>Do you have any recipes you'd be willing to share? I only have the one in John's book and I found this one somewhere...
>BLUE CHUN GLAZE c/9-10
>4210 G-200 Feld.
>180 EPK
>2720 Flint
>900 Whiting
>880 Dolomite
>170 Zinc oxide
>260 Tin Oxide
>---------
>10,200
>plus 400 Rutile
> 50 copper carbonate
>
>Does that sound wierd to anyone? There's no iron in it. I havn't had time to test either yet, just wondering....
>
>
--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
http://www.luepottery.hwy.com.au
Des & Jan Howard on mon 16 oct 06
Craig
If anyone wants to try the zinc containing oxidised route
the following could be a possibility.
potash feldspar 47
silica 27
limestone 17
talc 7
zinc oxide 2
Orton C12 (in a faster firing kiln or lower in hot spots).
Blue/white Jun effect. White satin microcystals at lower cone,
ocassionally white sugar crystals in sky blue matrix.
Works in reduction or oxidation, though zinc goes up
the spout under reduction. Bit of a bugger to handle when dry,
one could try, say, 1/2 - 3/4% of bentonite. Essential to keep the
alumina low.
Jacking up the zinc oxide might be interesting.
Ah! So many rabbits to chase.
Des
Craig Martell wrote:
> I was talking with Ian Currie some time back and he was thinking that
> oxidation chuns might be possible with the addition of some zinc
> oxide. I
> don't remember all the details that we mulled over but I can ask him
> again
> and see what the plan would be to pursue an oxidized chun.
--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
http://www.luepottery.hwy.com.au
Liisa Reid on wed 18 oct 06
This is interesting because the glaze I have used for many years
reliably turns iron blue. At times this has been to my frustration
when I wanted it to stay brown. The intensity can vary from a pale
blue to a deep midnight blue, almost black. If very thin it stays
brown. The shade of blue depends on the thickness of the glaze, and
on the concentration of iron. I have always thought of it as an
iron/ boron blue, but that hasn't seemed a sufficient explanation.
I have wondered about the zinc, but what I read just said it makes
muddy browns.
Here's the recipe -
E Clear cone 5 to 6 oxidation
Gerstley Borate 19.3 (i use whatever it is that Laguna is
selling as gerstley borate - works fine)
Feldspar-g200 42.3
Talc-Nytal 7.1
Zinc Oxide 4.5
Silica 24.8
English China Clay 2.0
and here's a link to the some of the ways it turns out:
http://homepage.mac.com/liisar/PhotoAlbum4.html
ps the black glaze is Ron and John's Licorice.
Liisa
On Oct 15, 2006, at 1:38 PM, Craig Martell wrote:
> I was talking with Ian Currie some time back and he was thinking that
> oxidation chuns might be possible with the addition of some zinc
> oxide. I
> don't remember all the details that we mulled over but I can ask
> him again
> and see what the plan would be to pursue an oxidized chun.
>
> regards, Craig Martell Hopewell, Oregon
Maid O'Mud on wed 18 oct 06
Did I miss something? Does the iron come from the clay body?
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: "Liisa Reid"
> This is interesting because the glaze I have used for many years
> reliably turns iron blue. At times this has been to my frustration
> when I wanted it to stay brown. The intensity can vary from a pale
> blue to a deep midnight blue, almost black. If very thin it stays
> brown. The shade of blue depends on the thickness of the glaze, and
> on the concentration of iron. I have always thought of it as an
> iron/ boron blue, but that hasn't seemed a sufficient explanation.
> I have wondered about the zinc, but what I read just said it makes
> muddy browns.
>
> Here's the recipe -
>
> E Clear cone 5 to 6 oxidation
> Gerstley Borate 19.3 (i use whatever it is that Laguna is
> selling as gerstley borate - works fine)
> Feldspar-g200 42.3
> Talc-Nytal 7.1
> Zinc Oxide 4.5
> Silica 24.8
> English China Clay 2.0
>
> and here's a link to the some of the ways it turns out:
>
> http://homepage.mac.com/liisar/PhotoAlbum4.html
>
Liisa Reid on thu 19 oct 06
That's the really interesting thing. There are no colorants in the
glaze. The blues are from the iron in the slip, which is under the
glaze. An effect caused by the boron in the gerstley borate, and
perhaps the zinc oxide. That's why I am intrigued by Craig's quote
from Ian Currie, since I have suspected that. I am wondering if
with some tweaking this could be a path to a faux cone 6 oxidation
chun.
Liisa
On Oct 18, 2006, at 10:45 PM, sacredclay wrote:
> Liisa, this recipe doesn't list any addition of colorants. Are you
> sure that's it? Then which chemical is creating the blues? Thanks!
> Kathryn in NC where the temps are going back up to the 80's. --- In
> clayart@yahoogroups.com, Liisa Reid wrote:
>>
>> This is interesting because the glaze I have used for many years
>> reliably turns iron blue. At times this has been to my frustration
>> when I wanted it to stay brown. The intensity can vary from a pale
>> blue to a deep midnight blue, almost black. If very thin it stays
>> brown. The shade of blue depends on the thickness of the glaze,
> and
>> on the concentration of iron. I have always thought of it as an
>> iron/ boron blue, but that hasn't seemed a sufficient explanation.
>> I have wondered about the zinc, but what I read just said it makes
>> muddy browns.
>>
>> Here's the recipe -
>>
>> E Clear cone 5 to 6 oxidation
>> Gerstley Borate 19.3 (i use whatever it is that
> Laguna is
>> selling as gerstley borate - works fine)
>> Feldspar-g200 42.3
>> Talc-Nytal 7.1
>> Zinc Oxide 4.5
>> Silica 24.8
>> English China Clay 2.0
>>
>> and here's a link to the some of the ways it turns out:
>>
>> http://homepage.mac.com/liisar/PhotoAlbum4.html
>>
>> ps the black glaze is Ron and John's Licorice.
>>
>> Liisa
>>
>>
>> On Oct 15, 2006, at 1:38 PM, Craig Martell wrote:
>>
>>> I was talking with Ian Currie some time back and he was thinking
> that
>>> oxidation chuns might be possible with the addition of some zinc
>>> oxide. I
>>> don't remember all the details that we mulled over but I can ask
>>> him again
>>> and see what the plan would be to pursue an oxidized chun.
>>>
>>> regards, Craig Martell Hopewell, Oregon
>>
>>
> _____________________________________________________________________
> _________
>> Send postings to clayart@...
>>
>> 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@...
>>
>
> ______________________________________________________________________
> ________
> 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.
sacredclay on thu 19 oct 06
Liisa, this recipe doesn't list any addition of colorants. Are you
sure that's it? Then which chemical is creating the blues? Thanks!
Kathryn in NC where the temps are going back up to the 80's. --- In
clayart@yahoogroups.com, Liisa Reid wrote:
>
> This is interesting because the glaze I have used for many years
> reliably turns iron blue. At times this has been to my frustration
> when I wanted it to stay brown. The intensity can vary from a pale
> blue to a deep midnight blue, almost black. If very thin it stays
> brown. The shade of blue depends on the thickness of the glaze,
and
> on the concentration of iron. I have always thought of it as an
> iron/ boron blue, but that hasn't seemed a sufficient explanation.
> I have wondered about the zinc, but what I read just said it makes
> muddy browns.
>
> Here's the recipe -
>
> E Clear cone 5 to 6 oxidation
> Gerstley Borate 19.3 (i use whatever it is that
Laguna is
> selling as gerstley borate - works fine)
> Feldspar-g200 42.3
> Talc-Nytal 7.1
> Zinc Oxide 4.5
> Silica 24.8
> English China Clay 2.0
>
> and here's a link to the some of the ways it turns out:
>
> http://homepage.mac.com/liisar/PhotoAlbum4.html
>
> ps the black glaze is Ron and John's Licorice.
>
> Liisa
>
>
> On Oct 15, 2006, at 1:38 PM, Craig Martell wrote:
>
> > I was talking with Ian Currie some time back and he was thinking
that
> > oxidation chuns might be possible with the addition of some zinc
> > oxide. I
> > don't remember all the details that we mulled over but I can ask
> > him again
> > and see what the plan would be to pursue an oxidized chun.
> >
> > regards, Craig Martell Hopewell, Oregon
>
>
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Ron Roy on sun 22 oct 06
This looks like a stable glaze - and the expansion is just right for the
clays I use - to avoid crazing.
RR
>Here's the recipe -
>
>E Clear cone 5 to 6 oxidation
>Gerstley Borate 19.3 (i use whatever it is that Laguna is
>selling as gerstley borate - works fine)
>Feldspar-g200 42.3
>Talc-Nytal 7.1
>Zinc Oxide 4.5
>Silica 24.8
>English China Clay 2.0
>
>and here's a link to the some of the ways it turns out:
>
>http://homepage.mac.com/liisar/PhotoAlbum4.html
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Lee Love on sun 22 oct 06
I found the Chun I use using Google:
lee love on thu 16 mar 06:
On a white body, I get Chun sky blue with this:
Paul's Chun cone 10/11 R
Custer 80
Whiting 7
Flint 7
Wood Ash 4
Bone Ash 2
Y. Ochre 1
Bentonite 1
For puple splash: 3% copper slip on raw body.
These types of glazes get their color the same way that the sky
does, from the bubbles in the glaze caused by the bone ash (P2O5
Phosphorus Pentoxide).
WHY IS THE SKY BLUE?
The blue color of the sky is due to Rayleigh scattering. As light
moves through the atmosphere, most of the longer wavelengths pass
straight through. Little of the red, orange and yellow light is
affected by the air.
However, much of the shorter wavelength light is absorbed by the gas
molecules. The absorbed blue light is then radiated in different
directions. It gets scattered all around the sky. Whichever direction
you look, some of this scattered blue light reaches you. Since you see
the blue light from everywhere overhead, the sky looks blue.
--
Lee in Mashiko, Japan
http://potters.blogspot.com/
"Let the beauty we love be what we do." - Rumi
"When we all do better. We ALL do better." -Paul Wellstone
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