The method described is applicable to enamelled articles that will, in service, be subjected to high temperature. Supplementary information on test temperature, test of heating, temperature measuring points, rate of temperature increase, duration of maintaining the test temperature, number of single heating and cooling tests and damage criteria of the evaluation the enamel finishes shall be derived from standard or other documents relating to the enamelled articles under test or, if appropriate, shall be the subject of agreement between the interested parties.