UV-protection characteristics of some clays

The potential of various clays including kaolin, smectite, mixed-layer series-dominated clay and mica-dominated clay to protect against ultraviolet (UV) radiation in the range 250–400 nm was examined. In order to understand the UV-protection abilities of the clays, properties of the clays were also characterized. The clays blocked UV radiation and bulk Fe2O3 content played a key role in the UV-protection properties, whereby the higher the bulk Fe2O3 content, the lower the UV-transmission level. However, UV-protection ability also depended on the expandability of the clay or the combination between clay mineral and mixed ointment.