Dishwasher safety is a concern in ceramic table ware, especially if the ware has been imported or made by a small company or potter.
Dishwasher safe ceramic ware is generally ware that is not overly absorbent and therefore will not water log in use over time (and therefore weaken and become a microwave oven hazard). Dishwasher safety also refers to the ability of ware to handle the changes in temperature it will be subjected to without cracking of the ware or the glaze. To produce ware that can withstand these temperature changes glazes must be thermal expansion compatible with the body (there are many articles and videos on this site about how to achieve that). The indicators of lack of expansion compatibility are crazing and shivering.
There is an increasing awareness of the food safety of glazes among potters. Be skeptical of claims of food safety from potters who cannot explain or demonstrate why.
|Glossary||Co-efficient of Thermal Expansion
Ceramics are brittle and many types will crack if subjected to sudden heating or cooling. Some do not. Why? Differences in their co-efficients of thermal expansion.
When sudden changes in temperature cause dimensional changes ceramics often fail because of their brittle nature. Yet some ceramics are highly resistant.
|Glossary||Clay Body Porosity
In ceramics, porosity is considered an indication of density, and therefore strength and durability. Porosity is measured by the weight increase when boiled in water.
Crazed ceramic glazes have a network of cracks. Understanding the causes is the most practical way to solve it. 95% of the time the solution is to adjust the thermal expansion of the glaze.
Shivering is a ceramic glaze defect that results in tiny flakes of glaze peeling off edges of ceramic ware. It happens because the thermal expansion of the body is too much higher than the glaze.
Ceramic glazes vary widely in their resistance to wear and leaching by acids and bases. The principle factors that determine durability are the glaze chemistry and firing temperature.