METHODS FOR TESTING CRAZING OF GLAZES CAUSED BY INCREASES IN SIZE OF CERAMIC BODIES1

Authors

  • H. G. Schurecht


  • 1

    Publication approved by the Director of the National Bureau of Standards, U. S. Department of Commerce and the National Terra Cotta Society. Presented at the Annual Meeting, American Ceramic Society, Atlantic City, N. J., February, 1928. (Terra Cotta Division.) Received March 5, 1928.

ABSTRACT

Investigations to determine the causes of a type of crazing which develops on certain glazed ceramic wares, some time after firing, revealed the fact that in many cases such crazing is caused by an expansion of the body. This is probably due to the combination of water with the body, while the glaze remains practically constant in size. A body may be tested for this type of crazing by placing the glazed specimens in an autoclave and subjecting them to a steam pressure of 150 to 175 pounds per square inch for one hour. Bodies showing the least tendency to develop this type of crazing are those which have a low porosity, are not very soluble in sulphuric acid, and have a low ignition loss above 110°C.

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