the theory As the name suggests, double cleansing is the Korean process of cleaning your face twice before layering the remainder of your evening skincare. The first cleanse flushes away the majority of oil based impurities including pollutants, makeup, sebum, bacteria and layers of sunscreen. The second picks up what the first misses and also effectively removes perspiration, cell debris and dirt.   According to Dr Susan Mayou, consultant dermatologist at London’s Cadogan Cosmetics clinic: Make-up is now formulated for its staying power, so it often needs a double cleanse to remove it thoroughly. Research shows that when skin isn’t properly cleaned, the surface layer can prevent active ingredients from…