Storage hardening is a phenomenon specific to natural rubber, which leads to an increase in bulk viscosity, usually characterized by the Mooney viscosity (MV) and Wallace plasticity (P0) (De Vries, 1927). The increase in the viscosity upon storage is not a desirable property of natural rubber as a raw material because this means a change in its processing behavior. However, the technological aspect of this has been overcome (Sekhar, 1964),