Ultraviolet protection factor (UPF), the way of measuring UPF is very complex, can be divided into (in vitro) and vivo (in) in human body. The actual values are also converted by a very complicated formula.
The sun will cause photoaging, causing skin spots, freckles and so on. Over the long sun, the skin absorbs too much ultraviolet radiation, leading to skin cancer. Light people can cause melanin deposition, dark skin, so summer anti ultraviolet is very important
UPF UV resistance index
Consumers of SPF (also called Sun Protection SPF index, Factor) were probably but most people for having heard it many times, do not know UPF, UPF is the index of anti ultraviolet textiles, according to Australia South University School of textile science and technology Welles report, white in the sun, the time limit of skin erythema in about ten minutes. When wearing UPF20, the time for erythema can be extended to twenty times, up to two hundred minutes (more than three hours). Similarly, if the umbrella with UPF30, the skin erythema can be extended by 30 times, up to three hundred minutes (five hours).
Usually the skin more white, more light, generally speaking, the same in the sun, white people are most likely to bask in red, then yellow, and finally black. Basically, the textile itself has ultraviolet shielding effect, the more heavy clothes, UV shielding effect is good