A finishing oil is a vegetable oil used for wood finishing. These finishes are a historical finish for wood, primarily as means of making it weather or moisture resistant. Finishing oils are easily applied, by wiping with a cloth. They are also simply made, by extraction from plant sources with relatively simple processing. Historically, both of these were considerable advantages over

varnish Varnish is a clear transparent hard protective coating or film. It is not a stain. It usually has a yellowish shade from the manufacturing process and materials used, but it may also be pigmented as desired, and is sold commercially in various ...

es, that depended upon exotic imported plant resins, complex preparation and careful application with expensive brushes. The two most important finishing oils, to this day, are linseed oil and tung oil.

Linseed oil Linseed oil, also known as flaxseed oil or flax oil (in its edible form), is a colourless to yellowish oil obtained from the dried, ripened seeds of the flax plant (''Linum usitatissimum''). The oil is obtained by pressing, sometimes followed by ...

is extracted from the seeds of the

flax Flax, also known as common flax or linseed, is a flowering plant, ''Linum usitatissimum'', in the family Linaceae. It is cultivated as a food and fiber crop in regions of the world with temperate climates. Textiles made from flax are known in ...

plant, already extensively grown for the production of

linen Linen () is a textile made from the fibers of the flax plant. Linen is very strong, absorbent, and dries faster than cotton. Because of these properties, linen is comfortable to wear in hot weather and is valued for use in garments. It also ...

. The raw oil may be used, but it cures poorly and leaves a sticky surface. Normally boiled linseed oil is used. This has been prepared beforehand by boiling with

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

, in the form of lead oxide, or with

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

salts. Modern boiled oils use a lead-free metallic

drier Dryer (or drier) may refer to: Drying equipment * Hair dryer * Hand dryer * Clothes dryer, also known as a tumble-dryer * Belt dryer * Desiccant, a substance that absorbs or adsorbs water * Grain dryer, for storage grain bins * Oil drying agent, a ...

added cold, such as cobalt resinate. Old linseed oil finishes yellow with age, owing to oxidation with the air. Linseed oil was also widely used for the production of

oilcloth Oilcloth, also known as enameled cloth or American cloth, is close-woven cotton duck or linen cloth with a coating of boiled linseed oil to make it waterproof. Manufacture Boiled linseed oil was prepared by a long boiling of linseed oil with me ...

, a waterproof covering and rainwear material, formed by coating linen or cotton fabrics with the boiled oil. Sunday, 7 March 2021 Tung oil is pressed from the nuts of the

tung tree ''Vernicia fordii'', usually known as the tung tree (, ''tóng'') is a species of flowering plant in the spurge family native to southern China, Myanmar, and northern Vietnam. It is a small to medium-sized deciduous tree growing to 20 m tall, wit ...

. Raw tung cures better than raw linseed and so it is often used in this form. As tung oil yellows with age less than linseed, it is favoured for high quality and furniture work. Most modern finishing oils use a blend of oil and a thinning agent such as

white spirit White spirit (AU, UK & Ireland)Primarily in the United Kingdom and Australia. In New Zealand "white spirit" can also refer to Coleman fuel (white gas). or mineral spirits (US, Canada), also known as mineral turpentine (AU/NZ), turpentine substitu ...

. Raw oils tend to be applied too thickly, leading to a thick layer that cannot cure effectively and so remains sticky. A thinned oil is easier and more reliable to apply. Such commercial mixtures also contain metallic driers to improve their performance. There are also mixtures sold as finishing oils. These are classed as 'long oils', predominantly oil with some varnish added or as 'short oils' which are predominantly varnish, with some oil.

Danish oil Danish oil is a wood finishing oil, often made of tung oil or polymerized linseed oil. Because there is no defined formulation, its composition varies among manufacturers. Danish oil is a hard drying oil, meaning it can polymerize into a solid for ...

is a popular long oil finishing oil. Spar varnish is a short oil varnish, used for added flexibility and elasticity.

References

Wood finishing materials Varnishes {{woodworking-stub