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Lapis108

Pinging noise in plates

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Hi, 

I wondered if I could have some expert advice. I recently bought some Portuguese stoneware dinnerware from a commercial company. The plates keep pinging and small cracks keep appearing but under the glaze. They were quite expensive and I love them but don't want to keep them if this is a problem.  Just some lines that don't seem to be harbours for bacteria but worried about the integrity of the plates and if this is normal! Thanks for any help.  

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Under what conditions do the plates ping/ While they just sit on the shelf, while they are being used, while they are being washed?

Post some pix of the plates if you can with closeups of the cracks...

Edited by JohnnyK

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If you can see cracks under the glaze then there are cracks in the glaze that you can't see.  I would return them if you plan to eat off of them,  if they are just for show you can keep them.  They won't break apart  just get more crazing in the glaze.   Denice

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Very likely glaze is crazing and has cracks. If yes, this will continue and most potters do not consider them food safe. You can often verify this at its early stages with a dry erase marker. Color heavily and when lightly wiped off often reveals the micro cracks in the glaze. My opinion, return them, if crazed they  likely will be more fragile as well.

Edited by Bill Kielb

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Lapis:

"Potugese >stoneware<  going to give an answer for other potters as well. The pinging sound I suspect is due to cristabolite inversion: a problem more specific to >stoneware.<  cristobalite inversion occurs as the pieces are cooling! not heating up. Potters who like to peek or crash cool around. 450F subject stoneware pieces to thermal shock at almost the exact temperature cristabolite formations are at their inversion range: beta to alpha. 

the clay body is compromised: the glaze will soon follow. 

Tom

 

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