The question of how important a surface seal (e.g. by glazing, slipping, or burnishing) is for cooking pots is addressed. Uptake by mass of chosen foodstuffs was examined at a surface of known area, over a given time. Uptake was measured as increase in mass of ceramic slabs of standard size. The general pattern observed was a large initial increase followed by smaller increments. The food itself thus seems to act as a sealant. Absorption of food does not ruin its functionality as a container or cooking vessel. Surfaces can be wiped off, and no spoiling of the substances taken up by the ceramic could be induced by high heat and humidity. It is observed that heating in cooking will sterilize the ceramic, and the carbonized layer will further seal it.