This study represents the first attempts at a systematic study of light scattering in polycrystalline materials both in the visible and infra-red region where all parameters responsible for scattering are independently varied. Light is scattered by voids and second phase particles. Light is also reflected and refracted by grain interfaces of random crystal orientations. With sufficient optical density of the sample, multiple scattering from voids, grain boundaries or second phase particles becomes the significant scattering mechanism in polycrystalline material. The diffuse scattering envelope width is measured and various scattering mechanisms are identified with respect to the way they influence this scattering width. Existing theories are reviewed and it is shown how these theories can qualitatively account for the observed behavior.