Metal Marking Behavior and Testing of Porcelain Tableware

The term "metal marking" is widely used to define the common phenomenon of tableware glazes being damaged by metallic cutlery. Appearing as unaesthetic gray marks and scratches resulting from normal conditions of use, these defects deeply affect the performance of ceramic products, especially in intensive environments, such as in the hospitality industry. The scope of this article is to establish a comprehensive review of the phenomenon, focusing on the physical and chemical mechanisms involved in the process, and their interactions and consequences. It also intends to list the different methods normally followed to avoid or at least reduce this defect, in order to enhance the durability of porcelain dishware. This manuscript also provides a review of the different testing methods developed and used by the tableware industry and technical centers to quantify the ability of porcelain tableware to produce metal marks. To face the current lack of any international or at least national standard testing procedure that would permit a reliable comparison of products, a new metal marking test developed at the Technological Center for Ceramic and Glass (CTCV) is presented as an alternative to common tests normally based on knives as a marking tool.