Donna Kat on mon 12 mar 07
cone 6 oxidation (Kaolin and Ball Clay tested).
I realize this is an old post but I am trying to confirm whether this is
or is not a stable glaze.
On
http://www.frogpondpottery.com/glazestability/glaze0022.html
you state that this version of Weathered Bronze glaze is stable.
If I understand correctly, Pete Pinnell reformulated the recipe
specifically so that it would be stable and a true cone 6 glaze with the
following recipe. Could you please comment. Thank you, Donna
On Fri, 28 May 2004 11:34:22 +0200, Alisa Clausen
wrote:
>Glaze test for Pete Pinnell's Seafoam, cone 6 oxidation.
>John Hesselberth has tested this glaze for Copper Leaching and recommends
this glaze for decorative use only.
>
>Source: Clay Times
>Credited to: Pete Pinnell
>
>Firing ramp:
>100c p/h to 600c (212f - 1112f)
>150c p/h to 1100c (330f - 2012f)
>100c p/h to 1220c (212f - 2228f)
>5 min. soak
>cool down max. to 800c
>Hold 1 hour
>Shut off kiln
>
>Recipe:
>
>9.6 Frit 3134 used Frit J
>51.3 Kona F-4 Feldspar used Forshammer spar
>25.5 Strontium Carb.
>13.6 Grolleg China Clay
>
>ADD
>5. Copper Carb.
>5.0 Titanium Dioxide
>
>can experiment with 3,4 5 percent additions of Copper Carb. However,
Pete notes, unlike the glaze bases with Spodumene,
>the copper increments made no difference in the color.
>
>
>Note: All raw materials are measured up or down to the nearest whole
decimal.
>Colorants or additives to a 100 gram test batch are measured in percent
to the 100 gram test batch.
>
>Results:
>Applied thick.
>A mat glaze that is well melted and very smooth surface. The color is a
strong aqua green. The glaze is well covering and has a slight sheen,
although mat. Where it is thicker, is more sheen than where thinner,
but green in both areas. Has a lush and thick look overall.
>
>
>Tested same glaze with Ball Clay instead of Kaolin.
>Resulted in a very similar glaze, but is slightly darker in overall
color. It is not as uniform in color or as bright as the recipe with
Kaolin. It has an appearance that the aqua color is higher surface, over
a darker ground. With Kaolin the glaze has an even color, with Ball Clay,
there is more color play on the surface.
>
>Regards from Alisa in Denmark
>
>
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Donna Kat on thu 22 mar 07
cone 6 oxidation (Kaolin and Ball Clay tested).
I'm sorry for reposting this but I fear that it was lost in the Conference
black hole. The Studio administrators are concerned with these 2 glazes
and are thinking of pulling both of them. These are really beautiful
glazes and it would be nice if they could be made food safe. Is that
possible given the ingredients? Pinnell's original weather bronze green
is listed as 'stable' but not food safe on the frogpondpottery site. Is
that true for his reformulated Seafoam Green?
Red Green (cone 6 electric)
Frit 3134 2700
Gerstley 1500
Spodumene 4000
EPK 1800
Tin Oxide 650
Copper Carg 480
Pinnell's Seafoam Green (cone 6 electric)
Frit 3134 9.6
Kona F-4 Feldspar 51.3
Strontium Carb 25.5
Grolleg China Clay 13.6
ADD
Copper Carb 5.0
Titanium Dioxide 5.0
John Hesselberth on thu 22 mar 07
cone 6 oxidation (Kaolin and Ball Clay tested).
On Mar 22, 2007, at 3:51 PM, Donna Kat wrote:
> I'm sorry for reposting this but I fear that it was lost in the =20
> Conference
> black hole. The Studio administrators are concerned with these 2 =20
> glazes
> and are thinking of pulling both of them. These are really beautiful
> glazes and it would be nice if they could be made food safe. Is that
> possible given the ingredients? Pinnell's original weather bronze =20
> green
> is listed as 'stable' but not food safe on the frogpondpottery =20
> site. Is
> that true for his reformulated Seafoam Green?
>
> .
Hi Donna,
I did not say Weathered Bronze Green was not food safe. I said I did =20
not recommend it for food surfaces. In the comments sections I =20
explained that it was likely to metal mark and would sometimes =20
pinhole if applied too thickly. It is actually quite resistant to =20
leaching if fired to a full cone 6 or a little above. Fired to cone 5 =20=
I suspect it would leach a lot. I also have to add that even though I =20=
have thoroughly tested this glaze and find it to be stable, that is a =20=
bit surprising from looking at the unity formula and comparing it to =20
other glazes I have tested. I have also had one potter tell me that =20
it did not pass the vinegar test for her--I don't know why.
I leach tested Pete's Seafoam about 3 years ago right after he =20
published it in Clay Times. It leaches badly. Much, much more that =20
Weathered Bronze Green. It did not even cleanly pass the vinegar test =20=
for me. It's silica level is too low and I doubt it fully melts with =20
the relatively low level of boron. So I am all for them pulling =20
Seafoam Green unless it can be limited to sculptural/decorative work--=20=
not easy to do in a shared studio.
I have no data on Red Green, but I would not personally use it on =20
functional work without testing it. It has a very unusual =20
composition--see the unity formula below--with high lithia, boron, =20
and alumina and only barely enough silica. Its high level of copper =20
carbonate is worrisome.
Regards,
John
--------------
Recipe Name: Red Green
Cone: 6
Firing: Oxidation
Amount Ingredient
2700 Frit--Ferro 3134
1500 Gerstley Borate--9/97
4000 Spodumene--Gwalia
1800 Kaolin--EPK
10000 Total
Additives
650 Tin Oxide
480 Copper Carbonate
Unity Oxide
.321 Li2O
.179 Na2O
.005 K2O
.042 MgO
.453 CaO
1.000 Total
.539 Al2O3
.469 B2O3
.004 Fe2O3
2.507 SiO2
.002 TiO2
.002 P2O5
4.6 Ratio
65.2 Exp
Comments:
-----------------------------------
Calculations by GlazeMaster=99
www.masteringglazes.com
------------------------------------
Donna Kat on sat 24 mar 07
cone 6 oxidation (Kaolin and Ball Clay tested).
On Thu, 22 Mar 2007 16:19:39 -0400, John Hesselberth
wrote:
>On Mar 22, 2007, at 3:51 PM, Donna Kat wrote:
>
>> I'm sorry for reposting this but I fear that it was lost in the
>> Conference
>> black hole. The Studio administrators are concerned with these 2
>> glazes
>> and are thinking of pulling both of them. These are really beautiful
>> glazes and it would be nice if they could be made food safe. Is that
>> possible given the ingredients? Pinnell's original weather bronze
>> green
>> is listed as 'stable' but not food safe on the frogpondpottery
>> site. Is
>> that true for his reformulated Seafoam Green?
>>
>> .
>Hi Donna,
>I did not say Weathered Bronze Green was not food safe. I said I did
>not recommend it for food surfaces. In the comments sections I
>explained that it was likely to metal mark and would sometimes
>pinhole if applied too thickly. It is actually quite resistant to
>leaching if fired to a full cone 6 or a little above. Fired to cone 5
>I suspect it would leach a lot. I also have to add that even though I
>have thoroughly tested this glaze and find it to be stable, that is a
>bit surprising from looking at the unity formula and comparing it to
>other glazes I have tested. I have also had one potter tell me that
>it did not pass the vinegar test for her--I don't know why.
>
>I leach tested Pete's Seafoam about 3 years ago right after he
>published it in Clay Times. It leaches badly. Much, much more that
>Weathered Bronze Green. It did not even cleanly pass the vinegar test
>for me. It's silica level is too low and I doubt it fully melts with
>the relatively low level of boron. So I am all for them pulling
>Seafoam Green unless it can be limited to sculptural/decorative work--
>not easy to do in a shared studio.
>
>I have no data on Red Green, but I would not personally use it on
>functional work without testing it. It has a very unusual
>composition--see the unity formula below--with high lithia, boron,
>and alumina and only barely enough silica. Its high level of copper
>carbonate is worrisome.
>
>Regards,
>
>John
Sorry, I apparently do not communicate well (I already know that). Please
note that I never said that you said it was food safe. If I were you, I
would be upset if I had... I was trying to get clarification on your 'not
food safe' and 'stable' and to double check that you had actually declare
Seafoam as unstable. It was wishful thinking on my part that you had not
delared one or the other to be "NOT FOOD SAFE" but rather 'unknown if food
safe'. I'm very disappointed to hear that the reformulated glaze is even
further off the mark than the cone9 version.
It is a shame that neither of these glazes is usable for funcional ware. I
vinegar tested the Red Green and it is not even close to being 'stable'
(the acid etched it considerably).
Thank you for your opinion on this.
Donna
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