tungolje

Tungolje (tung oil) is a drying oil obtained from the seeds of the tung tree (Aleurites fordii and related species). It has been used for centuries as a wood finish and protective coating, especially in East Asia, and later in Europe and North America after the tree was cultivated more widely.

Chemically, tung oil is rich in eleostearic acid, a fatty acid with conjugated double bonds that allow it to polymerize and form a hard, water-resistant film when exposed to air. Pure tung oil penetrates wood fibers and cures by oxidation, producing a clear to slightly amber finish that enhances grain and color without forming a thick surface film like some varnishes.

Applications include finishing furniture, floors, boats, and outdoor woodwork. Tung oil is valued for its water resistance, flexibility, and relatively natural appearance. Commercial products range from raw, cold-pressed tung oil to heat-treated or polymerized blends and "tung oil finishes" that mix resins and solvents to improve drying time and durability.

Advantages of tung oil include good penetration, moderate durability, and a matte to satin sheen. Limitations include slow curing time for pure oil, possible darkening of light woods, and susceptibility to solvent-based stains unless used in modified formulations. Safety considerations note that oil-soaked rags can undergo spontaneous combustion if improperly stored; tung oil is generally of low acute toxicity but may cause skin sensitization in some individuals.

Tung oil is often compared with linseed oil; each has distinct drying properties and aesthetic effects, leading users to choose based on desired performance and appearance.