This is new information for me. (Not the comparison aspect, but the surface energy...) I know several hardness scales are based primarily on measuring the elastic limit of the material. If I conclude the elastic limit is governed in large part by surface energy, would I be far from the mark?Nor is it unique to employ scales based upon comparison. Hardness scales are such. Although these are based on surface energy, there are other factors in play so that SE alone does not determine hardness.