A simple, generalizable, inexpensive method is demonstrated to synthesize Janus colloidal particles in large quantity. At the liquid-liquid interface of emulsified molten wax and water, untreated particles adsorb and are frozen in place when the wax solidifies. The exposed surfaces of the immobilized particles are modified chemically. Finally, wax is dissolved, and the inner surfaces are modified chemically. Gram-sized quantities or more of Janus particles can be synthesized by taking this approach.