In the past, some glazed roofing tiles have exhibited damage that only became visible after a certain period of time. Moreover, not all tiles in one production batch were affected. Producers of glazed ceramic building products as well as engobe and glaze producers are therefore called upon to assure the quality of their products in the long term by means of specific tests. The standard applicable to clay roofing tiles, DIN EN 1304, does not include any specific test requirements for the durability of engobes and glazes. Moreover, the occurring discoloration phenomenon cannot be replicated with the applicable frost resistance test. To avoid new incidents of damage, in the absence of their own specific standards for quality control, the manufacturers conduct tests that are applied in the ceramic tile industry as specified in DIN EN 14411. These will be briefly presented in the talk and assessed in respect of their applicability for engobes and glazes, because not everything currently being tested is expedient or necessary. To conclude, proposals for approval procedures/approval logs are provided.

Kerstin Hohlfeld, Keramik-Institut GmbH, Meissen