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Pottery/Sharp Nodules on Glazed Pieces


QUESTION: A piece that I had painted with clearglaze came out of the kiln with maybe 40 raised pointed nodules.  I did read an answer to someone named Claudia regarding what she described as bubbles.  Since these little nodules are hard (I actually sanded them down), am wondering if this is a separate issue?  Could it be caused by some loose particles in the kiln that may have been blowing around when the fan is operating during the firing process?  Or is it an issue to do with the firing itself?
Thanks for any info you can provide.

ANSWER: Dear Carol,

    Thank you kindly for your recent question. It would be difficult to identify the problem without actually seeing it. Bubbles are easy to identify as that is exactly what they look like, however, they too are hard. Nodules could be from a particular raw material not reaching maturing temperature, but unless I could see a photo of the flaw, there is really know way of identifying it.

    As for loose particles, this is possible, but I don't know of a fan blowing on the inside of a kiln. No kiln that I know of has a fan. There is really no atmospheric movement within the kiln during firing, except if it is a wood kiln, where fly ash can adhere to the ware during firing.

    If you can provide a photo in the future, I will be happy to identify the flaw and give you information on correcting it. Sorry that I couldn't be of more help.

    Always at your service.

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

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

QUESTION: Hi,  Thanks for your quick response. Do you have any thoughts on whether it would be beneficial to refire the vase keeping in mind that I did lightly sand down the nodules. Or should I leave well enough alone?

Dear Carol,

    Thank you for your follow up question. Yes, go ahead and re-fire the piece to maturing cone. It won't hurt it if you do and maybe the glaze will smooth out upon cooling.

    Let me know how it turns out. It helps to know so I can provide information to future questionnaires. Good luck!

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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