Winsor and Newton - Artisan Water Mix - Fast Drying Med - 75ml - Fast Drying Meduim is a very popular medium as it speeds the drying of oil colour by about 50%, allowing further layers to be applied more quickly. The formulation has been improved and this has helped to wet the colour better. It thins the colour and increases gloss and transparency. When painting in layers it can substitute linseed oil and be combined with water and/or Thinner to maintain fat over lean.