"Merino wool offers excellent UV protection as the merino fibers are efficient absorbers of potentially harmful UV-A and UV-B radiation. Research has shown that wool absorbs radiation throughout the entire UV spectrum, whereas untreated cotton, nylon, acrylic and silk are poor absorbers of UV radiation. A study done with thin summer fabrics (<160 g/m2) showed that all merino wool samples had an UPF factor of at least 40." (Hilfiker et al 1996, Reinert et al 1997, Haerri 2000 and Gamblicher et al 2001)