Sun protective material, Coloured scanning electron micrograph (SEM). Factors that affect the level of sun protection provided by a fabric, in approximate order of importance, include weave, color, weight, stretch, and wetness. The less open or more dense the fabric (weave, weight, stretch), the better the protection. In addition, some textiles and fabrics employed in the use of sun protective clothing may be pre-treated with UV-inhibiting ingredients during manufacture to enhance their effectiveness. Magnification: x100 when printed at 10 centimetres across.