An instrument is proposed for the visualisation and measurement of mixtures of small and large particles. The original concept was to use spectral extinction for sub-micron particles and scattering patterns for larger sizes. However, the former method is sensitive to the refractive index, which may be unknown or vary with wavelength in an unknown way. The experiments demonstrated this to be a problem. The forward scatter, on the other hand, is not so sensitive to this. It is shown here that the combination of scattered intensity as a function of both angle and wavelength provides scatter diagrams for which there is good agreement between theory and experiment. The influence of quite small volume fractions of particles as small as 0.3 mu m mixed with 90 mu m particles is easily seen. The scatter diagrams suggest the use of image analysis for size measurement and quality control.