An equation more complete than any existing one in literature for the upper size limit of flotation was presented and tested against mercury drops, spherical particles of sulfur, and paraffin-coated grains of different solids. It was demonstrated that flotation tests combined with the derived equation make it possible to characterize and measure floatability and hydrophobicity of spherical and irregular particles in the form of the equilibrium and detachment angle of the bubble-particle aggregate. The maximum size of floating particles values and the equilibrium as well as detachment contact angles were determined for various hydrophobic materials including sulfur, pyrite, mercury, germanium, silicon, talc, fluorite, silicon carbide, silver iodide, ilmenite, arsenic oxide, diamond, graphite, molybdenite, and boric acid. Also resulting from this study is the confirmation that the monobubble Hallimond tube is a valuable tool for characterizing and comparing flotation of different systems.