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Pottery/Applying Copper Carbonate to Refire


QUESTION: Hi, I'm experimenting with low fire barium matt glazes. I brushed the glaze onto my sculpture then sprayed a solution of copper carbonate and water onto the raw glaze. I want to have a variation in colour of turquoise and royal blue with small amounts of metallic copper. I wasn't happy with the fired result so I sprayed parts of the sculpture with more of the copper solution and re-fired, but the glaze only seemed to accept a small amount of copper, while the original layer of colour seemed to have moved around. How can I get the copper to stay on? Do I need to add something else to it?

The clay is Scarva Earthstone 20, bisqued to 900C
The glaze is satin matt, fired to 1060C
The glaze recipe is :-
Barium          31.5
Nepheline Syenite  23.5
Quartz          20.5
China clay         15.0
Lithium          9.5
Bentonite          2.0

I hope you can help, many thanks

ANSWER: Dear Janice,

    Thank you for your recent question. First, lets address the movement of the glaze on re-fire. During firing, raw glaze materials bond to each other at different rates during each degree of temperature rise. When the kiln begins to cool, the patterns and colors are set. However, during a re-fire, especially when a solution is re-applied, further fusion of the raw materials will occur during the maximum temperature. This is because at the highest temperature, the glaze is fluid and will begin to move. Once again, when the kiln cools, the glaze is fixed and permanent. So, this is why the glaze seems to change or move about the piece.

    As for re-application of the copper carbonate, I suggest you add a small amount of CMC gum to the solution to suspend the copper carbonate. Also, add a tsp of honey to the mixture to create a sticky base on which to apply the solution. You may also want to lightly sand the piece with 800 grit sand paper to create a bondable surface for the copper. This should keep the copper carbonate on the piece for firing.

    I hope this is what you were looking for. If you have further questions, please feel free to contact me again at any time. I'm always at your service. Good luck.

Ms. Ti Phillips
Earth Stoke 'N Fire Pottery Studio and Artist Retreat

---------- FOLLOW-UP ----------

QUESTION: Hi Ti, thank you for your answer. I've got some gum tragacanth which I used instead of CMC for cake decoration,  would that be OK to use? Also, I'm not sure if the honey might clog up my spray gun so could I apply the honey to the sculpture where I want the copper to stick and spray on to that?
Many thanks

Dear Janice,

    Thank you for your follow up question. Yes, gum tragacanth will work for this instance. Also, applying the honey to the sculpture is also acceptable.

Ms. Ti Phillips
Earth Stoke 'N Fire Pottery Studio and Artist Retreat


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Ti Phillips


Will answer any questions on hand building, wheel, glaze, firing. Speciality questions to include those in glaze calculation and development, firing techniques. Please do not send questions on identifying pottery. Although I would love to add this to my question topics, I have a retreat to run as well as the studio and volunteering on AllExperts, and therefore do not have the available time to research indentification and marks. Thank you for understanding.


Experience includes 30 years in pottery design and education. Have taught online and studio classes worldwide for the last 20 years. Own a pottery retreat specializing in firing techniques. Have 12 years solid experience in glaze calculation and formulation as well as problem solving in glaze chemistry. I am the first potter in the United States to have developed a complete package of pottery equipment blueprints for a studio. The blueprints include wheels, kilns, studio furniture, wedgeboards, raku kilns, slab rollers, ball mills and studio tools.

Alliance of Pottery Artists Worldwide Association

Ceramic Industry - PPP Wyndstryder Press - Pottery Journal

University of Sciences and Art's of Oklahoma, studied under Professor Jaymes Dudding.

Awards and Honors
Potter of the year with APAWA, various awards for showmanship and design.

Past/Present Clients
Available upon request.

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