Heloisa Nunes on sat 29 apr 06
I hope this goes through finally and the tech problems are over. Looking
forward to exchange ideas with clayarters during this autumn in Sao Paulo.
By the way, got a very nice combo with Lana's Burgundy over the "Celadon "
clear - Mottled wine color over turquoise. Nice Surprise.
> Hello, Clayarters,
> Once more I come for help with all the experienced people of clayart. Lots
> of questions!
> Thank you in advance for any inputs. I wish I can have a glaze software
> soon
> and learn to use it so that these adjustments are made easy. I have been
> having some trouble installing software in my computer.
> My firing profile is the same as Ron Roy's webpage, slow cooling (-125oF)
> down to 1400oF.
> I live in Brazil, I don't have the material analyses (merchants here do
> not
> seem to carry it), so I know some guess work will happen.
> My clay is a white local clay, shrinkage between 12-16 %, I don't have
> cracks but it feels a bit low in plasticity (it breaks appart like raku
> clays) compared to Highwater clays (which I used in the US).
>
> First, has anyone tested Lana Wilson's Burgundy for food safety?
> Lana Wilson Burgundy
> Gerstley Borate 20.68
> Neph. Sy 16.29
> E. P. Kaolin 11.34
> Whiting 19.52
> Flint 32.16
> Tin Oxide 5
> Chrome Ox. 0.2
> ( I got a wonderful dark burgundy color and apparent good fit with this
> one)
>
> Secondly, I am having trouble with crazing. Lana's Burgundy and the ""
> celadon" clear below apparently don't craze. I have tryied to read the
> threads on clayart about it but I found myself confused about what to do
> (I
> need glaze making for dummies probably). I could not figure out if the
> crazing was from too much or too little expansion, and what to do to fix
> it.
> Should I use Lana Wilson's Burgundy and the clear/celadon that is working
> expansion rates? Should I adjust all glazes to have the same expansion as
> these two?
>
> "Celadon" clear
> (works fine with my clay, no apparent crazing but sometimes it gets rough
> where thick with slow cooling -125oF to 1400 like Ron Roy's profile)
> Soda Feldspar 51
> Whiting 13
> Quartz 25
> Zinc Oxide 8
> Bentonite 3
> Add Copper Carbonate 3
> (green)
>
> I would like to try other clears (including MC6 clear/licorice), but the
> other tree clears I have tryied crazed a lot. I wonder what should I do
> with
> them, and how to adjust so that I do not have crazing...In addition, the
> tough thing is that I also would love that it worked with my firing
> profile
> so that I don't have to do a specific firing(electricity here is
> expensive)
> and I can work with the burgudy layering other glazes...
>
> Third and last question. I got these two recipes below here in Brazil, and
> I
> wonder if they are reliable/food safe
>
> Paulos' White (matt white)
>
> Potash feldspar 33
> Whiting 16
> Quartz 33
> Dolomite 8
> Titanium Dioxide 8
> Bentonite 2
>
> Paulo's Black (matt black)
>
> Soda Feldspar 42.3
> Dolomite 21.2
> Kaolin 29.5
> Quartz 7
> Add
> Cobalt Carbonate 1.5
> RIO 10
>
> Other recipes as a beginner potter I have been using are the Dry Yellow
> Pumpkin (which Ron said is underfired - thank you so much for the help,
> Ron)
> just for decorative purposes. I love the color, have added rust for brown
> spots, and hope I can later on play with it and make it work at cone 6 for
> food safe pieces.
> I also tested Fall's Creek Shino with Albany slip and got a wonderfull
> shiny
> chocolate brown with beige variegation where thin. It also did not present
> any apparent crazing.
>
> That's it. Wow, a lot! Thank you so much for your help and I look forward
> to
> the discussion on the recipes.
> Heloisa Nunes
> São Paulo, Brazil
>
>
>
>
>
Brian Fistler on sat 29 apr 06
On Sat, 2006-04-29 at 19:13 -0300, Heloisa Nunes wrote:
[snip]
> > Secondly, I am having trouble with crazing. Lana's Burgundy and the ""
> > celadon" clear below apparently don't craze. I have tryied to read the
> > threads on clayart about it but I found myself confused about what to do
> > (I
> > need glaze making for dummies probably). I could not figure out if the
> > crazing was from too much or too little expansion, and what to do to fix
> > it.
> > Should I use Lana Wilson's Burgundy and the clear/celadon that is working
> > expansion rates? Should I adjust all glazes to have the same expansion as
> > these two?
> >[snip]
The two glazes you mentioned that do not craze show a calculated
expansion of 7.43 (red) and 7.51 (clear). (As calculated by insight) I
know that with these expansion rates they would probably both craze on
the clay I use, 7.45 gives me delayed crazing (very slight after 3-4
weeks) so I like to keep my glazes down around 7.2-7.32 range as I've
never had any problem in that range.
What is a recipie of a glaze that you are having trouble with?
As to food safety, I'm certainly not an expert and would not hazard a
guess. You can always do dishwasher detergent and acid tests to check
for color/surface/texture changes which should give a good indication as
to it's relative durability.
Brian
Heloisa Nunes on mon 1 may 06
Thanks, Brian for offering help.
So much information that I forgot to put the recipes that did not work...For
the clear glazes, I got a lot of crazing in the following recipes:
Mark Burleson's Chun Clear (which got rough with the slow cooling and gave
me turquoise with 0.5 copper carbonate)
Soda Feldspar 38
Whiting 14
Zinc Oxide 12
Ball Clay 6
Silica 30
Marisa's Clear
Nepheline Syenite 23.1
Gerstley Borate 14.0
Silica 10.2
EPK 27.0
Bentonite 5
Do you adjust your Lana Wilson's recipe for less crazing? It is a lovely
glaze, and I did not make the freezer/boiling test yet. Now I am wondering
if it will survive, especially if I put in teapots...
thank you again and I look forward to any help you could offer.
Heloisa Nunes,
São Paulo, Brazil
Brian Fistler on thu 4 may 06
On Mon, 2006-05-01 at 21:24 -0300, Heloisa Nunes wrote:
> Thanks, Brian for offering help.
> So much information that I forgot to put the recipes that did not work...For
> the clear glazes, I got a lot of crazing in the following recipes:
>
> Mark Burleson's Chun Clear (which got rough with the slow cooling and gave
> me turquoise with 0.5 copper carbonate)
> Soda Feldspar 38
> Whiting 14
> Zinc Oxide 12
> Ball Clay 6
> Silica 30
>
> Marisa's Clear
> Nepheline Syenite 23.1
> Gerstley Borate 14.0
> Silica 10.2
> EPK 27.0
> Bentonite 5
>
On the Marisa's clear, I'm surprised you are getting crazing, are you
missing an ingredient above, or are you possibly getting shivering
instead of crazing? I'm showing a very low expansion on that of 6.8
The Chun Clear is showing 7.22, but if the problem is the roughness and
not crazing, it looks like is is probably under-firing, as it looks to
me to be under-fluxed. Is that possibly a cone 10 glaze, and not a cone
6? The Sodium & Potassium is at the low-end even for a cone 10 glaze,
especially considering there is no boron present either for flux. I
would guess that is probably why it is rough textured.
Brian
Heloisa Nunes on fri 5 may 06
Hi, Brian,
Thank you for your input!!!
Well, Mark Burleson's Chun Clear is stated as a cone 6 in the book... I
don't know , some people said that there were some typos in the book and
maybe I should take a look at that.
The other recipe, Marisa's clear, I asked the recipe again and this is what
I got:
Nepheline Syenite 46.20
Gerstley Borate 28
Silica 20.40
EPK 5.40
Bentonite 1
Copper Carbonate 12
I don't know if it is shivering. How do I know the difference?I will try it
again, though.
I hope I can figure it out with your help or shop for another clear. Thank
you again,
Cheers from São Paulo,
Heloisa
----- Original Message -----
From: "Brian Fistler"
To:
Sent: Friday, May 05, 2006 12:44 AM
Subject: Re: Help with glazes cone 6 ox
> On Mon, 2006-05-01 at 21:24 -0300, Heloisa Nunes wrote:
>> Thanks, Brian for offering help.
>> So much information that I forgot to put the recipes that did not
>> work...For
>> the clear glazes, I got a lot of crazing in the following recipes:
>>
>> Mark Burleson's Chun Clear (which got rough with the slow cooling and
>> gave
>> me turquoise with 0.5 copper carbonate)
>> Soda Feldspar 38
>> Whiting 14
>> Zinc Oxide 12
>> Ball Clay 6
>> Silica 30
>>
>> Marisa's Clear
>> Nepheline Syenite 23.1
>> Gerstley Borate 14.0
>> Silica 10.2
>> EPK 27.0
>> Bentonite 5
>>
>
> On the Marisa's clear, I'm surprised you are getting crazing, are you
> missing an ingredient above, or are you possibly getting shivering
> instead of crazing? I'm showing a very low expansion on that of 6.8
>
> The Chun Clear is showing 7.22, but if the problem is the roughness and
> not crazing, it looks like is is probably under-firing, as it looks to
> me to be under-fluxed. Is that possibly a cone 10 glaze, and not a cone
> 6? The Sodium & Potassium is at the low-end even for a cone 10 glaze,
> especially considering there is no boron present either for flux. I
> would guess that is probably why it is rough textured.
>
> Brian
>
> ______________________________________________________________________________
> 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.
>
Ron Roy on fri 5 may 06
Hi Brain, hi Heloisa,
I must concure - the clear has a very low expansion rate - and only adds to
76.3 - and the alumina and silica are way over for a cone 6 glaze - it
would just not melt - yes something missing.
The Burleson glaze will melt at cone 6 - in fact could use more alumina and
silica with that much zinc oxide. - the ratio is 10.89 - no chnace that
would go matte with a slow cool - are we sure of our materials here?
The expansion is not that high but I would expect it to craze on many clays.
RR
>On Mon, 2006-05-01 at 21:24 -0300, Heloisa Nunes wrote:
>> Thanks, Brian for offering help.
>> So much information that I forgot to put the recipes that did not work...For
>> the clear glazes, I got a lot of crazing in the following recipes:
>>
>> Mark Burleson's Chun Clear (which got rough with the slow cooling and gave
>> me turquoise with 0.5 copper carbonate)
>> Soda Feldspar 38
>> Whiting 14
>> Zinc Oxide 12
>> Ball Clay 6
>> Silica 30
>>
>> Marisa's Clear
>> Nepheline Syenite 23.1
>> Gerstley Borate 14.0
>> Silica 10.2
>> EPK 27.0
>> Bentonite 5
>>
>
>On the Marisa's clear, I'm surprised you are getting crazing, are you
>missing an ingredient above, or are you possibly getting shivering
>instead of crazing? I'm showing a very low expansion on that of 6.8
>
>The Chun Clear is showing 7.22, but if the problem is the roughness and
>not crazing, it looks like is is probably under-firing, as it looks to
>me to be under-fluxed. Is that possibly a cone 10 glaze, and not a cone
>6? The Sodium & Potassium is at the low-end even for a cone 10 glaze,
>especially considering there is no boron present either for flux. I
>would guess that is probably why it is rough textured.
>
>Brian
>
>______________________________________________________________________________
>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.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Brian Fistler on fri 5 may 06
On Fri, 2006-05-05 at 08:09 -0300, Heloisa Nunes wrote:
> Hi, Brian,
>=20
> Thank you for your input!!!
> Well, Mark Burleson's Chun Clear is stated as a cone 6 in the book... I
> don't know , some people said that there were some typos in the book an=
d
> maybe I should take a look at that.
> The other recipe, Marisa's clear, I asked the recipe again and this is=
what
> I got:
> Nepheline Syenite 46.20
> Gerstley Borate 28
> Silica 20.40
> EPK 5.40
> Bentonite 1
> Copper Carbonate 12
> I don't know if it is shivering. How do I know the difference?I will tr=
y it
> again, though.
>=20
> I hope I can figure it out with your help or shop for another clear. Th=
ank
> you again,
> Cheers from S=E3o Paulo,
> Heloisa
>=20
This is definitely a different recipe that you listed the first time...
It has much less EPK... you had EPK listed at 27 last time... not 2.7
As listed here this glaze is NOT a low expansion glaze and is much more
balanced, although it also has a higher expansion (7.66)
(Also, I think the Copper Carbonate you meant to type as 1.2, not 12.)
Are you trying to correct a batch of glaze you already have? If so, do
you have any access to any very-low expansion frits, like 3249? If so,
you could try adding up to 8 parts 3249.
The formula below shows a calculated expansion of 7.37 compared to the
original 7.66:
Nepheline Syenite 46.20
Gerstley Borate 28
Silica 20.40
EPK 5.40
Bentonite 1
Frit 3249 8.0
If you don't have access to 3249, you could also try adding a small
amount of additional silica which will reduce the expansion, but also
increase the melting point somewhat, but the original formula is already
pretty high in KNaO & boron, both of which are strong fluxes at cone 6,
so I would guess it will still melt fine... Test to make sure
Taking the silica to 25 without the frit would lower the Thermal
expansion to 7.46 which might be enough to prevent the crazing.
Orig. Revised 3249 Revised Silica
CaO .46 .43 .46
MgO .11 .18 .11
KNaO .43 .39 .43
Aal2O3 .49 .48 .49
B2O3 .37 .44 .37
SiO2 3.40 3.26 3.68
Therm expan 7.66 7.37 7.46
Si:Al Ratio 6.93 6.82 7.51
SiB:Al Ratio 7.69 7.75 8.26
Calculated LOI 8.14 7.55 7.79
If you're looking to start from scratch, there are a lot of glazes
utilizing Frit 3134 that are reliable (again, only good for you if you
have access to frits)
Brian
Brian K. Fistler on fri 5 may 06
On Fri, 2006-05-05 at 14:08 -0500, Ron Roy wrote:
> Hi Brain, hi Heloisa,
>
> I must concure - the clear has a very low expansion rate - and only adds to
> 76.3 - and the alumina and silica are way over for a cone 6 glaze - it
> would just not melt - yes something missing.
>
> The Burleson glaze will melt at cone 6 - in fact could use more alumina and
> silica with that much zinc oxide. - the ratio is 10.89 - no chnace that
> would go matte with a slow cool - are we sure of our materials here?
> The expansion is not that high but I would expect it to craze on many clays.
>
> RR
>
Oops, missed the ZnO as flux... That's why you have (some of) my money
and I have your book... because you're the expert here :)
Brian
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