Compositions including a water releasing agent and golf ball cores made from such compositions having a high hardness gradient are disclosed. The type and concentration of the components in the composition, including the water releasing agent, affect the hardness and hardness gradient of cores made from the composition and, thus, can be used to produce a golf ball having desirable performance characteristics. Cores made from the composition may be cured using infrared radiation to further increase the hardness and hardness gradient of such cores. Cores cured using infrared radiation may have a center and a skin with hardness greater than the hardness of the center to produce a high hardness gradient.