eoteceramics Posted April 22, 2014 Report Share Posted April 22, 2014 Hi can anyone help with this problem I've had lately. After firing ,small pieces have been flaking off and beneath is a white powder like patch. Appreciate any theories. Photo attached. Thanks Julia Link to comment Share on other sites More sharing options...
Pres Posted April 22, 2014 Report Share Posted April 22, 2014 Could be that you have plaster in your clay body. Link to comment Share on other sites More sharing options...
Marcia Selsor Posted April 22, 2014 Report Share Posted April 22, 2014 Calcium pitting. Sometimes it is in the clay..not necessarily plaster, just an impurity. Call the supplier and mention it. Could be just the source in nature. Marcia Link to comment Share on other sites More sharing options...
TJR Posted April 22, 2014 Report Share Posted April 22, 2014 I agree with Pres. Looks like a plaster pop-out. If you have any plaster lying around your studio, this could be the source. Plaster bits take moisture from the air, then they expand and blow out. Very frustrating. TJR. Link to comment Share on other sites More sharing options...
Marcia Selsor Posted April 22, 2014 Report Share Posted April 22, 2014 Calcium pitting is the same as plaster pitting which is also calcium. It can come naturally in clay ..bits of shells from ages ago for example. Which ever it is, it ruins the surface. Just saying it may not be plaster. I saw earthenware from one supplier that was continuously pitting from this. They had several batches that had contaminated clay. It ruined pieces in my friends production line. He switched suppliers and clay. Marcia Link to comment Share on other sites More sharing options...
eoteceramics Posted April 22, 2014 Author Report Share Posted April 22, 2014 Thanks for replies, I don't think it could be plaster but it was pug milled clay so could have been contaminated with something, very frustrating Link to comment Share on other sites More sharing options...
williamt Posted April 22, 2014 Report Share Posted April 22, 2014 Unless it was your clay and your pugmill, it could have anything, including plaster. Does the place you got it from have plater wedging table or do slip molding? Either of those could introduce plaster. Or like others have said, could be natural. Though, you'd think if it was natural, it would be kinda consistent over the piece. Link to comment Share on other sites More sharing options...
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