A method and apparatus for estimating the adhesion properties of a surface of an article by holding the article so that the surface is facing downwards and placing a droplet of liquid against the surface. A pre-processed food product is provided and is processed by rapidly heating the food product. The system comprises a rev counter which measures the rpm of the suction valve system, as well as a control unit which is connected to the power source, the rev counter and the engine management system. The power has an associated phase angle and, within a time duration, a plurality of alternating on periods and off periods, one set of adjacent on and off periods defining a duty cycle. , wherein the difference in CTE values between the glass substrate and the decorative porous inorganic layer is within 10\xd710\u22127\xb0C.