This paper addresses the interfacial area generation in Kenics static mixers using a new method. A statistical description of the microstructure development is obtained using the extended mapping method, which. As restricted to systems with negligible interfacial tension. However, the layered structure created in a Kenics area good example where interfacial tension does not play an important role (the layered structure is retained), The extended mapping method is adopted to the special flow conditions in spatially periodic flows. The efficiency of the interface generation for different mixer layouts is compared and additional attention is given to the distribution of the interfacial area across the mixer. It is shown that the extended mapping method enables us to find the blade configuration that optimizes the mixing performance, in accordance to the standard mapping method, but now including much more details concerning the microstructure development in this chaotic flow.