A Crazing-Free Window for Low-Cost Glazes: The Thermal Expansion Mismatch a Fired Glaze Can Tolerate on a Porous Earthenware Body

This paper addresses earthenware glazes that craze into a network of fine cracks weeks after firing, weakening the ware and harbouring dirt. It presents a permissible expansion-mismatch window for glaze fit on porous earthenware, derived entirely from stated assumptions and a computation whose code and full output accompany the paper. The sweep covers expansion mismatch between glaze and body from -1.5 to 1.5 per million per degree C. The headline outcome is: largest safe positive mismatch 0.5; stress at plus1 mpa 46.7; stress at plus0p5 mpa 23.3; crazing threshold mismatch 0.75. These figures identify a specific operating point or bound that a workshop can apply directly, and they also show how quickly performance deteriorates away from it. No kiln was built, no ware was fired, and nothing was measured for this study. SIMULATED, NOT MEASURED.