Review of Kose Clear Turn White Vitamin C Mask. you can use it two ways. If you wish for a relaxing spa experience, heat it up slightly in a warm water bath for 5-10 minutes before usage. Else, you could go the usual way and chill in the refrigerator to help refine pores while the mask sets. After washing your face, prep with toner and smooth the sheet mask out evenly to fit your face. There are eye pads included so you could mask the skin around your pretty peepers as well. It was recommended to use the mask consecutively for a couple of weeks to see an obvious change.