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Pottery/Glaze Under Firing


Hi, I thought the glaze firing was done after 4 hours, and later found out it should take around 7. I have 2 questions; one can I just turn back on the kiln while it is still warm now that I see that it is not fired/glazed properly and if so how would you turn it back on (one switch at a time or all 4 at once)
I put in a new cone and hope that it works, would you suggest leaving it for 7 hours or until the cone melts?
As well, does it take 7 hours for second firing?
Thank you, Karen.

Dear Karen,

Thank you for your recent question. We have had ice storm electricity outages so my response to you is not a timely as usual. Please forgive me.

As for firing your glaze ware. You could have re-fired the kiln in the normal manner by firing as you did before with a new cone in the sitter. Never turn all the switches on at once as the kiln will heat too rapidly and cause ware breakage.

Anytime there is an under fire on glazes, you can re-fire the glaze in a new firing, just as you did before. However, you will probably receive the same results if the kiln is not firing appropriately. If you are using a kiln sitter and the kiln is turning off prematurely, check the sitter to assure the cone is bending correctly. If it has, then the kiln did fire to maturing temperature, no matter what you have heard about the length of time a kiln should fire a glaze firing. Some kilns fire faster than others and will show this by turning off sooner than what is expected. When firing, we are not looking at time, but rather heat work. If a kiln is full, it will fire to maturing temperature faster than an empty kiln because of the heat work from one piece of ware to the other. So if your cone bent correctly, then your kiln fired correctly.

To be sure that your sitter is working properly, add a cone to a shelf during the firing to assure the cones are reaching maturing temperature.

I hope this helps you. Once again, I am sorry about the timeliness of the answer due to the ice storm. Please contact me at any time if you have further questions. I'm 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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