Ivor and Olive Lewis on wed 8 feb 06
Dear Friends,
For some time I have been searching for a stable compound of Copper that =
seemed to have potential as a glaze pigment. Most of the natural Copper =
Silicate materials are hydrates and decompose to Black Copper Oxide when =
heated. Copper oxides is soluble in acids, forming Copper Acetate with =
Vinegar. The following information seems to show promise and deserves =
exploration.
Source: http://www.jcsparks.com/painted/pigment-chem.html#Egypt
Egyptian blue ("frit," "Pompeiian blue"):
Origin and History: Very stable synthetical pigment of varying blue =
colour. It is one of the oldest man-made colors commonly found on wall =
paintings in Egypt, Mesopotamia and Rome. Many specimens, well over 3000 =
years old, appear to be little changed by the time.=20
Making the Pigment: Heating a mixture of a calcium compound (carbonate, =
sulfate or hydroxide), copper compound (oxide or malachite) and quartz =
or silica gel in proportions that correspond to a ratio of 4 SiO2 : 1 =
CaO : 1 CuO to a temperature of 900=B0C using a flux of sodium =
carbonate, potassium carbonate or borax. The mixture is then maintained =
at a temperature of 800=B0C for a period ranging from 10 to 100 hours.
Chemical Properties: Calcium copper silicate, CaCuSi4O10. It is =
insoluble in acids even in warm temperatures.
Artistic Notes: It has a discreet covering power. It can be used in =
fresco. Not advised in tempera, oil and encaustic.
Note the comment on stability. Insoluble in Acids ! !
Someone with a glaze calculator might like to put forward a series of =
recipes to match the Seger Formula: 4 SiO2 : 1 CaO : 1 CuO. =
Wollastonite might be considered as a potential ingredient
I would like to know if this would remain stable up to cone 10 and would =
like to test any recipes which I can accomplish with ingredients to =
hand.
Hope someone will join me in this one.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
John Hesselberth on wed 8 feb 06
On Feb 7, 2006, at 7:21 PM, Ivor and Olive Lewis wrote:
> Someone with a glaze calculator might like to put forward a series =20
> of recipes to match the Seger Formula: 4 SiO2 : 1 CaO : 1 CuO. =20
> Wollastonite might be considered as a potential ingredient
Hello Ivor,
Interesting thoughts/observations!
Using wollastonite and silica the appropriate wt%s to give a 4/1 mole =20=
ratio of SiO2 to CaO are shown below. There would be very little of =20
anything else in that mix so you could source your fluxes, as you =20
suggest, from sodium/ potassium carbonates and borax to your hearts =20
content. I would start with an amount that might approximate an =20
earthenware glaze composition and increase as needed to get a decent =20
melt. The second recipe below shows a possible starting point using =20
borax and soda ash.
How much copper to add depends on the specific form you choose to =20
use. I'm sure you are aware that what we potters call copper =20
carbonate is usually relatively pure CuC03.Cu(OH)2 -- often called =20
basic copper carbonate. But you could also choose to use one of the =20
copper oxides. I'll let you do that math depending on what you have =20
available and its purity.
Regards,
John
------
Recipe Name: Copper Stain Experiment 1
Cone: Color:
Firing: Surface:
Amount Ingredient
43.8 Wollastonite
56.2 Silica
0
100 Total
Unity Oxide
.005 Na2O
.047 MgO
.948 CaO
1.000 Total
.025 Al2O3
.004 Fe2O3
3.783 SiO2
153.7 Ratio
56.8 Exp
Comments:
-----------------------------------
------------------------------------
Recipe Name: Copper Stain Experiment 2
Cone: Color:
Firing: Surface:
Amount Ingredient
17.8 Wollastonite
22.9 Silica
51.1 Borax
8.2 Soda Ash
100 Total
Unity Oxide
.538 Na2O
.022 MgO
.44 CaO
1.000 Total
.011 Al2O3
.882 B2O3
.002 Fe2O3
1.76 SiO2
154 Ratio
98 Exp
Comments:
-----------------------------------
Calculations by GlazeMaster=99
www.masteringglazes.com
------------------------------------
Ivor and Olive Lewis on thu 9 feb 06
Dear John Hesselberth,
How much Copper is there in each of your recipes?
Using Copper Oxide (black). Wollastonite and Silica and a bit of mental =
arithmetic I came up with the following to which I would add 10% =
Anhydrous Sodium Carbonate=20
Copper Oxide (CuO) 21.28%
Wollastonite 30.85%
Silica 47.87%
Add=20
Sodium Carbonate 10.00%
These seem to be good "Ball Park" values to me
Thanks for coming to the party.
Best regards,
Ivor
John Hesselberth on thu 9 feb 06
On Feb 9, 2006, at 2:04 AM, Ivor and Olive Lewis wrote:
> How much Copper is there in each of your recipes?
Hello Ivor,
I always test with 5% copper carbonate and 6% rutile. No good reason
for the rutile except that is does aid stability and that is what I
built up a large amount of my own data on. So I always test in that
standardized way. Ron and I have recommended using a maximum of 5%
copper carb--and preferably a max of 4%--for several years now. Even
in the best of glazes copper leaching really goes through the roof
when you get up to 6 and 7%.
Regards,
John
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