We all (sooner or later) have noticed that foods relatively high in protein (especially those low in fat) are very prone to sticking to a pan, or in general to any non-specially-coated metal surface. For example really lean white fish, which is almost all protein, is one of those devils which will always want to stick. Likewise, egg whites can stick. To some extent, almost any food that doesn't have a generous amount of easy-rendering fat seems to stick, but higher protein is more sticky. To counteract this tendency, one learns to compensate by putting some kind of fat (usually oil or butter) into the pan in advance of the food. Most people seem to get the best result by preheating the dry pan some, then adding the oil, letting it get up to temperature, then adding the food. I was just trying to ask myself what would be a simple and general sketch of what is going on on the surface of a pan when sticking takes place, and in particular: 1) what features of a material (density, chemical composition, elasticity, specific heat,etc.) 2) and of the state of the surface (temperature, roughness, etc.) have a dominant role in the physics of such a system. 3) Which phenomena (lubrication, intermolecular forces, order-disorder phase-transitions, etc.) are more likely to be responsible for what we experience in our every-day life.