In some embodiments, a method for determining initial conditions for a transition from an initial reaction to a target reaction to minimize (or substantially minimize) the amount of off-grade material produced during the transition, and optionally also process control variables for implementing the transition. Some embodiments also include the steps of setting the reaction conditions to determined initial conditions and then implementing the transition. In some embodiments, a product property that can cause production of more off-grade product during the transition than can any other of the properties is identified as a primary property, and process control variables for implementing the transition are determined so that the product produced during the transition goes off-grade due to the primary property, and due to each of at least one other product property, at the same or substantially the same time, and preferably also so that each non-primary property reaches a value compliant with the target specification set as late as possible but not later than the time the primary property reaches a value compliant with the target specification set.