Holbein Duo Aqua Oils were created to have the same handling qualities and characteristics of oil colors while being non-toxic and easy to clean up. A combination of the finest quality pigments and linseed oil that has been treated with a surfactant (surface active agent); Holbein Duo Aqua Oils can be treated as traditional oils. In fact， it is recommended that paintings created with Holbein Duo Aqua Oils be left to dry for approximately 6 months before varnishing， just like traditional oil paintings. Use with Holbein Duo Aqua Oil Mediums for myriad possibilities. When only water is used the Aqua Oils will dry with a slight matte finish in less time than traditional oils mixed with an oil medium.