Sandy091

The inside of one part mold cups bloat badly. Not evident after bisque, only after glaze firing. No evident pattern. Happens with a variety of glazes. Have fired over 100 small cups for glaze testing a year ago- no problem. Now the interiors of sever slip cast items are bloating. Same kiln, several different glazes, and different boxes of casting slip. Help! ( this is Miller cone 6 porcelain.