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Pottery/How to Counter Effects of Tin Oxide in Glaze


Recently when mixing up a batch of JJ's Turquoise glaze (cone 6) I mistakenly added 3% tin oxide (formula does not call for any tin).  This glaze is matte when mixed correctly and with the addition of the tin it is extremely dry and powdery when fired.  As tin is so expensive I would rather not have to dump the batch and  mix up another 5000 grams.  Do you think there is any way to salvage this - at this point I don't care if it is different in appearance than normal JJ's - I just want a useable cone 6 glaze.  Thanks for any advice you may have!

JJ's Turquoise

Strontium Carb 25%
Neph Sy          54%
EPK          6%
Silica          7%
Lithium Carb     2%
Copper Carb     4%
Bentonite          2%

Dear Monica,

Thank you for your recent question. To correct your glaze without affecting the glaze outcome, it is suggested you use CMC Gum to increase the binding ability and decrease the viscosity of the glaze. However, this has to be done in very small amounts and tested to assure the glaze doesn't become too fluid and roll or melt off the ware. This also has to be performed with the glaze dry.

Begin by weighing your glaze. You will need to know exactly how much glaze you have left in the jar before adding the CMC Gum. Be sure and subtract the weight of the container the glaze is in.

To complete the remaining steps, you may need to break up the glaze into a powder again. This solely depends on how the glaze dried and whether the raw materials compacted together. If they did, them use a rubber mallet, while wearing a dust mask, to break up the glaze into a powder form again.

Next, you will need to mix the CMC Gum solution. The standard solution for a powdery glaze is 1 part CMC gum to 3 parts water. So, mix 600 grams of water and 200 grams of CMC Gum in a separate lidded container.

To add the CMC solution, calculate the amount needed by multiplying the amount of dry glaze you have by .05.

For example:

4500 grams glaze x .05 = 225 grams of CMC solution needed

Once mixed, add water back to the glaze to create the application thickness required for the glaze. Calculate the CMC solution needed and add to the glaze. Mix using a jiffy mixer or mixer you normally use to mix your glazes.

Test the glaze on a test tile to assure the glaze works as needed. If the glaze continues to have issues, add an additional 50 grams liquid weight of the CMC solution to the glaze, mix and retest on a test tile until the glaze performs as needed.

I hope this helps you. If you have any questions, please contact me at anytime. I am always at your service.

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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