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Pottery/Bisque Underfire

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Question
Hello pottery experts!

I did a bisque firing with mostly cone 10 clay pots to be use in a wood firing in a few weeks!
I have a large oval kiln, it was full,
I programmed kiln to
Cone 04 bisque - Slow
With a hold of 4 hours
The kiln said completed at 1576 degrees!!!
I called Olympic help line for some advice, the staff said that the kiln controls are program to also know when things are done!
That she thought it will be fine, but to check bisqueware when kiln cool down.
I check this morning, and I compared the bisqueware fired with some old bisque pices that I have.  They don't quite match in color, very close but not 100%
I want your opinion, would they be ok to go in the wood kiln firing just like they are?  or should I tried to re-fire them? and if so how?
Thank you so so much!
N

Answer
Dear Nadia,

    Thank you for your recent question. Olympic is correct. When firing a kiln, depending on how the settings are adjusted, the kiln may not reach temperature, but will have fired to cone. Reaching cone is based on the length of firing and temperature of the kiln. Since you programmed a slow fire with a long hold, the kiln turned off when it reached cone temperature, not firing temperature.

    However, you may have also set the kiln to fire up to a particular temperature before holding, and failed to set the cone temperature increase. Make sure you follow the instructions in the kiln manual for setting the program.

    Finally, there is no need to set a hold on bisqueware. Holding temperatures are only used for speciality glazes that you want a unique effect on. For instance, crystalline glazes in which a hold will allow the crystals to grow larger. So, in the future, just fire to cone 04 for bisqueware.

    As for your current ware, it should be all right to fire in the wood firing because the clay has been changed to permanent and all chemical waters removed. To prevent breakage during firing, heat the wood kiln slowly.

    Although I stated that they should be fine, if you are working with pieces that you can't afford to loose, and if you have the time, then re-fire to cone 04 without a soak. Also, place a cone in the kiln to assure the kiln is firing to temperature.

    I hope this has answered your questions. If you have further questions, please feel free to contact me at any time. Always at your service. Much luck to you.

Sincerely,
Ms. Ti Phillips
Earth Stoke 'N Fire Pottery Studio and Artist Retreat
www.earthstokenfire.com

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Ti Phillips

Expertise

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

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.

Organizations
Alliance of Pottery Artists Worldwide Association

Publications
Ceramic Industry - PPP Wyndstryder Press - Pottery Journal

Education/Credentials
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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