Methods and apparatus for making and sensing ice. Also, apparatus and methods for sensing the change of phase of a substance. In one embodiment, a fringe-effect capacitor is placed proximate to a substance, such as water, which is undergoing a phase change, such as the change of phase from the liquid state to the solid state. During this change, the dielectric constant of the substance changes, and thereby changes the electrical flux between conductors of the fringe-effect capacitor. Also, apparatus and methods as described above, and using a capacitor but not a fringe-effect capacitor.