A systematic study of the terpolymerization of butyl acrylate/methyl methacrylate/vinyl acetate (BA/MMA/VAc) was conducted. In this stage of the study, batch emulsion terpolymerizations were performed in a 5 L stainless steel pilot plant reactor. The experiments were designed using a Bayesian (optimal) technique. The polymers produced were characterized for conversion, composition, molecular weight, and particle size. Conversion, terpolymer composition, number- and weight-average molecular weight, and average particle size results are discussed in light of the influence of seven factors and the interaction of these factors. The factors studied include monomer feed composition, initiator concentration, chain transfer agent concentration, impurity concentration, initiator type, emulsifier concentration, and temperature. A "two-stage rate" phenomenon, similar to that occurring in bulk co- and terpolymerization and emulsion copolymerization of acrylic/vinyl acetate systems was observed in the conversion, composition and molecular weight data. Furthermore, an interesting yet often ignored effect of impurities on emulsion polymerization kinetics was explained.