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Oil Finishing

Tung Oil or China Wood Oil

Tung oil is extracted from the nuts of the Tung tree (Aleurites Fordii) that grows throughout Asia. It is also known as China Wood Oil and has been used as a wood finish in China for centuries. It gives a rich lustrous character to the wood, deepening and enhancing the colour. It can be easily touched up and scratches and surface damage easily repaired by reapplying top coats and will develop a patina that only improves with age.

Pure tung oil is food safe and can be used on chopping boards and utensils that are used for food preparation. Although it’s worth noting that as it’s pressed from a nut, people with severe allergies are advised to avoid its use.

Tung oil is one of the few oils that are classified as ‘drying oils’. Other oils that fall into this category are linseed, walnut, soybean and poppyseed. A drying oil is an oil that hardens to a tough film, not through evaporation of the solvents as many finishes do, but rather they undergo a chemical reaction when exposured to air.

Most oil finishes on the market use tung oil as their base, they are often extended with cheaper oils, anti-fungals and synthetic hardeners. By going back to basics and using pure tung oil you can ensure a high quality nontoxic finish with no chemical additives.

Thinning

The solvent for thinning tung oil is Citrus Terpene or d-Limone, extracted from waste citrus peelings using the distillation process. Gum turpentine extracted from the resin of live trees can also be used. In some literature, ‘white spirit’ is prescribed, this is the American term for mineral turpentine.

Tung oil is best used when thinned 1:1 with solvent. Apply a generous amount onto the timber and wipe the excess off with a clean cotton cloth, don’t let the oil sit or pool for too long.

The first coat can be applied using 600 grit wet and dry sandpaper, this will give a very smooth finish when wiped off. Some areas will soak up the oil differently as there is always variation in grain density. Tung oil is best when a series of thin coats are applied over a period of several days, leaving it to cure properly between coats.

Once the tung oil is properly cured to a hard finish, (after a week or so) it can be buffed, either by hand with a soft cloth or with a lambswool buffing pad for larger areas. This will give you a beautiful low gloss sheen and enhance the detail of the natural timber features.

Note: Rags with tung oil on them shouldn’t be left bundled up, there is a possibility the may combust, rinse them and spread them out to dry after use.

Prior to applying Tung oil finish.
 
After the Tung oil has been applied.
An example of a dry Tung oil finish.