Double Boiled Linseed Oil causes it to polymerize and oxidize, effectively making it thicker and shortening its drying time. It dries more completely and quickly and forms a film on the surface. Double Boiled Linseed oil is a dark amber colored oil having a distinctively sharp smell. This oil is mainly used indoors. It is very water resistant, and also a rust inhibitor. Double Boiled Linseed oil is used in the paint industry. The drying time is much shorter than Raw Linseed Oil. It can be mixed with MTO or thinner. It is also used in the maintenance of paint brushes.