A system for controlling the operation of a blow molder (4,6) to affect the crystallinity of generated containers, the system comprising: at least one processor and operatively associated memory, wherein the at least one processor is programmed to: receive an indication of a crystallinity of at least one container produced by the blow molder (4,6), characterised in that the at least one processor is further programmed to: receive from at least one camera (202,214) at least one image showing a portion of the at least one container produced by the blow molder; derive from the at least one image an indication of a clarity status of the at least one container, wherein the indication of the crystallinity of the at least one container comprises the indication of the clarity status; receive from a material distribution system an indication of a material distribution of the at least one container; execute a model, wherein the model relates a plurality of blow molder input parameters to the indication of crystallinity and the material distribution and wherein a result of the model comprises changes to at least one of the plurality of blow molder input parameters to move the material distribution towards a baseline material distribution and the crystallinity towards a baseline crystallinity; and implement the changes to the at least one of the plurality of blow molder input parameters. at least one processor and operatively associated memory, wherein the at least one processor is programmed to: receive an indication of a crystallinity of at least one container produced by the blow molder (4,6), receive an indication of a crystallinity of at least one container produced by the blow molder (4,6), characterised in that the at least one processor is further programmed to: receive from at least one camera (202,214) at least one image showing a portion of the at least one container produced by the blow molder; derive from the at least one image an indication of a clarity status of the at least one container, wherein the indication of the crystallinity of the at least one container comprises the indication of the clarity status; receive from a material distribution system an indication of a material distribution of the at least one container; execute a model, wherein the model relates a plurality of blow molder input parameters to the indication of crystallinity and the material distribution and wherein a result of the model comprises changes to at least one of the plurality of blow molder input parameters to move the material distribution towards a baseline material distribution and the crystallinity towards a baseline crystallinity; and implement the changes to the at least one of the plurality of blow molder input parameters. receive from at least one camera (202,214) at least one image showing a portion of the at least one container produced by the blow molder; derive from the at least one image an indication of a clarity status of the at least one container, wherein the indication of the crystallinity of the at least one container comprises the indication of the clarity status; receive from a material distribution system an indication of a material distribution of the at least one container; execute a model, wherein the model relates a plurality of blow molder input parameters to the indication of crystallinity and the material distribution and wherein a result of the model comprises changes to at least one of the plurality of blow molder input parameters to move the material distribution towards a baseline material distribution and the crystallinity towards a baseline crystallinity; and implement the changes to the at least one of the plurality of blow molder input parameters.