A method and system for making a golf ball core is disclosed. The method may generally include forming a golf ball core out of a raw core material. The golf ball core may be rapidly heated to begin curing (or vulcanizing) from the outermost surface toward the center of the golf ball core. Before curing the entire golf ball core, the golf ball core may be quenched to stop the curing process. As a result, the golf ball core may include an outer cured zone and an inner uncured zone. In this state, the golf ball core may be incorporated into a finished golf ball to be sold to consumers. Following a set of instructions provided with the golf ball, the consumer may heat the golf ball to customize the properties of the golf ball core, and, thus, the characteristics of the golf ball.