Oak is an open-pored wood. To properly treat oak, the pores must be sealed to prevent moisture from entering the wood. There are different products available to seal these pores, most of them classified as "drying oils." The time it takes for them to dry, the gloss and the frequency of treatment differentiates these oak wood treatments.
How It Works
Drying oils work by penetrating the pores and then polymerising. Polymerising means drying in the presence of oxygen. With repeated applications over a few weeks, a layer is built up creating a moisture barrier. The layer then becomes semi-permanent and can be polished by hand to achieve a glossy finish. Once the finish is completely dry, it can then be coated with a coating such as varnish or lacquer, but it is not recommended to put a topcoat over any treated oak wood after it has been thoroughly treated with oil.
Drying oils are plant-based derivatives. Almost any oil can be used to treat oak wood[ among the most common are linseed, teak, tung, olive, vegetable, poppy and walnut. These household oils work well but in some cases, dry too slowly for commercial applications. Different plant based oil will impart slightly different colours to the wood and will have different appearances after the application is complete. Natural plant based oils are the cheapest treatment, and usually applied by hand with a soft cloth.
Because of the long drying time of plant based oak wood treatments, procedures have been taken to process the oil for more workability and faster drying times. By heating certain oils like linseed oil and tung oil, a chemical reaction is created in the molecules of the oil. The oil becomes, "pre-polymerized." Pre-polymerised oil dries within a few hours and is widely known as "Danish oil." Stain, solvents and drying chemicals are also added to the Danish oil oak wood treatment to give the oak depth, colour and control over gloss. Danish oil is popular for fine furniture and anywhere colour versatility is desired.
Where To Use It
For areas and items that do not have much sun exposure or traffic, such as chopping blocks, gun stocks, trim around wet areas like sinks and door trim, natural drying oils like linseed, vegetable, and olive oil work better than heat treated oils. For large applications like decks, stairways and doors, pre-polymerised drying oils work better. Heat-treated drying oils are also produced in larger quantities and have other additives that make them suitable to apply with spray guns.
Other industrial products for oak wood treatment contain creosote that is injected into the wood at the sawmill or left to soak in large tanks. This type of treatment is reserved for high water exposure such as pilings, docks, signposts and large wooden beams. This type of treatment is recognised by a greenish tint, with the characteristic holes in the wood made from machinery that treated the wood at the mill. This type of oak wood treatment is not recommended for household use.