Simple optical techniques are described for the direct visual observation of the plasmon surface polariton dispersion curve, ω vs k, and of the shift in the dispersion curve from overcoatings of different thicknesses. To see the dispersion curve, a collimated beam of white light is dispersed by a prism, and then focused by a cylindrical lens onto the base of a second prism coated with a thin metal film. With this arrangement the attenuated total reflection spectrum is obtained with all the visible frequencies spatially resolved. The shift of the dispersion curve for coatings of different thicknesses is illustrated in a separate experiment using a specially constructed Langmuir wedge. This demonstrates the usefulness of plasmon surface polaritons for monitoring coatings with thicknesses of the order of nanometers. © 1980, American Association of Physics Teachers. All rights reserved.