This paper evaluates a method of measuring shear stress, in-situ, in polymer flows. The rupture response of two different dye containing polymeric microcapsules, CM511 and CM567, is examined in both an internal batch mixer and a lab scale single screw extruder (SSE), using ultraviolet/visible spectrophotometry (UV/VIS), colorimetric analysis (CA) and optical microscopy (OM). It is observed that both particles rupture over a wide range of shear stresses and times. In particular, both CM511 and CM567 begin to rupture at similar to 100 kPa, while complete rupture is only detected for the CM567 at average stress levels greater than or equal to similar to 230 kPa. Complete rupture for the CM511 is not observed over the average shear stress range investigated. The microcapsules further indicate the change in the melting mechanism in a SSE when the processing conditions are changed.