An emulsion polymerization process using a redox initiator comprising a reductant and an oxidant, wherein monomers are mixed into a carrier liquid, e.g. water, to make a pre-emulsion, which is then supplied to a reactor comprising one or more circulation loops, an outlet, and a circulation pump for circulating a reactor charge within the circulation loop, characterized in that the reductant is added to the pre-emulsion before it is mixed into the reactor charge and the oxidant is mixed into the reactor charge, e.g., via the water-phase feed.