Natural Wood Treatment
Natural wood treatment is growing in popularity due to environmental concerns of the traditional chemical preservers. Most of the methods are not as effective as chemical timber treatment.
Rot Resistant Wood
There are some timbers which are naturally resistant to rot, and these include Western red cedar, Huon pine, Ironbark and some species of cypress. Even using resistant species, only the heartwood is protected and the outside sapwood is still at risk.
This resistance is caused by organic chemical extractives, such as polyphenols, contained within the wood. Normally these extractives convert sapwood into heartwood, but they provide the wood protection from rot.
Unfortunately, many of the resistant species are expensive to use in timber construction. Many of these species are also logged in an unsustainable manner, which could lead to a risk of extinction for these trees.
Wood Composites
Wood composites as an alternative to timber protected via wood preservers. Wood composites are a mixture of plastics and wood, and they are highly resistant to rot. They do however deform in extremely hot weather.
Heat Treatment
Heat treatment may be used on timber as a wood preservative. When wood is heated, the sugars inside it break up making it less attractive to both fungus and insects. It also causes the protective chemicals naturally found within the wood to spread throughout it. Heat treatment also has other advantages, as it can stop wood deforming when wet, and increase weather resistance.
This natural wood treatment is not as effective as chemical alternatives in preventing rot and woodworm. Heat treatment causes the wood to darken in colour, and reduces the elasticity of the wood. This means drilling is required before nailing the wood, otherwise it will split.
Heat treated wood is recommended for use indoors, for applications such as wooden floors and kitchen components. It can also be used in furniture.
There are three common heat treatments in Europe, which are all similar in their method. Retiwood was developed in France, Thermowood in Finland, and Platowood in the Netherlands.
Linseed Oil Wood Preserver
Linseed oil is a type of natural wood treatment, which is made from the seeds of the flax plant. It was much more common in the past, before the invention of chemical wood preserver.
Boiled Linseed Oil
Linseed oil is usually combined with some solvents, which decreases the drying time of the preservative. This is known as ‘boiled’ linseed oil, despite the fact no heating of the linseed occurs. The addition of a solvent to the linseed oil may make it less of a natural product, although it is more natural than other chemical wood preservers.
Chemical timber treatment outperforms linseed oil in almost every way. Linseed oil does not protect against the sun, which destroys wood fibres. If the wood fibres are damaged, this increases the risk of insect and fungal attack.
There is a risk that the linseed oil will not dry, leaving a sticky residue on the surface which is very difficult to remove. Linseed oil also can encourage mildew growth. The solvent added to linseed oil to increase drying times can also be dangerous, containing chemicals such as arsenic, cadmium and nickel.
Tung Oil
Tung oil is an alternative to linseed oil, as it does not encourage mildew growth. However, it only penetrates the top layer of the wood.
Tung oil and linseed oil do not contain fungicide and so are not true wood preservers. They are more useful as a wood finisher than as wood preservative. They do provide protection against heat marks and damage such as scratching.