Abstract Processing variables have been examined for the prediction and control of mold shrinkage in directions pertinent to practical applications. (1) Of the total shrinkage of finished parts, more than 75% results from the press cure, and the remainder is the result of weight losses during the subsequent oven cure. (2) Mold shrinkage may be reduced by addition of CaO, bituminous coal fines, or epoxy resins. Shrinkage can be increased by addition of volatile materials. (3) Control of shrinkage may also be effected with acicular fillers or filler mixtures through fiber orientation in the elastomeric matrix in the desired direction. In the case of O-rings, inside diameter shrinkage values ranging from zero to three per cent can be produced in a controllable manner by blank preparation techniques commonly used in the industry.