The basic ingredient in oil paint, although many manufacturers substitute it with safflower or other oils these days for light colors and blues. Only one manufacturer remains who still uses the traditional stone ground cold pressed linseed oil as in the old master days: ‘Old Holland’. Linseed oil is often added to paint for various effects, such as ‘stand’ linseed oil used when glazing for its relative lack of yellowing and viscosity. An old process is sun bleaching oil in the presence of water. It dries faster than normal linseed oil and is best used as an ingredient in mediums. Hardware store linseed oil should never be used, it is boiled oil, the worst kind.