To determine the effect of solar irradiance on Stevia leaves, the testswere carried out simultaneously on two DSD, one where the surface wascompletely covered by a shadow-mesh, with a 60% solar irradiancefiltration rate, while the a second DSD did not have the mesh cover. Inboth cases, the solar dryers were operated with both natural and forcedconvection. The purpose of this experiment was to determine the effectof direct sunlight on the leaves during the drying process, particularlychlorophyll colour loss, which was assessed with a colorimetric study.