The term ‘varnish’ is a collective descriptor used for colorless materials containing drying oils (eg, linseed oil), resin solutions or mixtures thereof. The term ‘varnish’ comes from the Greek berniki = “veneer” or, possibly, from the name of the city of the Egyptian queen, Berenike, (known today as Benghazi), located in what is now Libya. Since ‘varnish’ is a generic term, it is better to use it in compound forms, for example: mineral oil varnish or linseed varnish, resin varnish.

The linseed oil varnish is a brown oil that gives off a characteristic odor, and is the most important varnish product. Wood oil varnish plays a subordinate role. Flaxseed varnish is obtained from linseed oil, to which drying agents (desiccants) are added, at a temperature of 140-150ºC, enhancing the drying capacity considerably. The coatings are solid, elastic and resist bad weather conditions. A thin layer of liquid varnish of linseed oil can be applied to the products that require treatment and this is dried, within 24 to 36 hours, due to the physical and chemical changes (polymerization of unsaturated fatty acids) in the form of transparent film with a strong adhesion. The high viscosity varnishes of linseed oil are used in printing inks as binders.