A method for adding an additive into a polymer melt, preferably a polyester polymer melt such as polyethylene terephthalate (PET), comprising: a. discharging a polymer melt from a reactor to form a discharged polymer melt stream, and b. solidifying said discharged polymer melt stream, and c. prior to solidification, feeding a portion of the discharged polymer melt stream to a slipstream to form a slipstream polymer melt, and d. feeding an additive into said slipstream polymer melt to form an additive containing slipstream, and e. feeding the additive containing slipstream to a location upstream from the feed location forming said slipstream.