Crystallization of honey occurs when the nectar is stored at too low of a temperature. Honey should optimally be kept at between 70 and 80 degrees Fahrenheit. If honey happens to crystallize, it doesn't mean that the honey has gone bad; it simply needs to be heated to return to its liquid form. Liquefying honey repeatedly won't change the integrity of the substance, so it can be done as often as necessary.
Fill a saucepan with 2 inches of water and heat over medium-low heat.
Place the jar of honey into the water. If your honey is being stored in a plastic container, scoop it into a glass jar to keep the container from melting when heated.
Heat the honey until it melts. The amount of time it takes will depend on the amount of honey and the extent of crystallization.