It is a property of certain concentrations of glycerine-water solutions, when in a state of steady flow, that the planes of equal shear in the liquid become visible in ordinary light, if viewed along a path tangent to the shear plane. This phenomenon has been used successfully to study a fluid-flow problem at the University of Michigan. The nature and scope of application of this optical property is currently being studied further. This report gives details of what may prove to be a useful tool in certain phases of experimental fluid-flow problems.