Abstract: Curing of rubber in a mold is disclosed wherein a desired modulus or viscosity for the cured rubber product is obtained on the basis of an equation developed from a relaxation phenomenon. The cure process may be isothermal and non-isothermal and is controlled in a manner to compensate for acceleration of the cure reaction due to an increase in carbon black filler loading and the effect thereof which broadens the relaxation spectrum. Control of the curing process for the rubber material according to the equation permits response to the effect of the presence of a filler which reduces the activation energy of the viscous flow and that the presence of the filler produces a small effect on the activation energy of the cure reaction.