A surface treatment that forms a film over the wood reduces and balances out these fluctuations in moisture content, thereby lengthening the life of wooden structures. Continual fluctuations in moisture content cause wood to swell and shrink, and this leads to splitting. Wood is a hygroscopic material that will absorb moisture from the air. Depending on the coating's intended use, the binder will form a more- or less-dense film that protects the surface from exterior moisture. The wood's cells absorb the binder and bind the pigment to the wood's surface. Typical binders used in translucent finishes for exterior use are drying oils, alkyds, or acrylics. The binder binds the pigment to the wood and provides protection from the elements A paint's binder also affects how long its colour will last – many people are all too familiar with how quickly an oilpainted blue house will fade. For example, the yellow and red pigments contained in iron oxides withstand UV radiation much better than organic blues. There are also differences in pigments – colour matters. A completely colourless wood stain or varnish does not provide any kind of UV protection, and the treated surface will therefore grey as fast as an untreated surface. In other words, the stronger and more opaque a wood stain's colour is, the better the protection it offers from the sun. The more colour particles there are, the slower the wood's surface ages. The pigment (that is, the colour particles) stops the UV radiation that attempts to break down the wood's surface cells and the lignin that binds them together. Tinted finishes provide protection from sunlightĪny translucent finishes that are used outdoors should be tinted. The only preparatory work required is washing or even just brushing the surface, followed by one coat of wood stain over the faded area. A translucent finish does not flake – it simply fades or blanches in the sun. One thing to note, however, is that a film-free or thin-film translucent finish is much easier to reapply than an opaque finish. Although translucent finishes do not last as long as opaque ones, there is great variation in how often they require maintenance.Ī translucent finish on the shadowy side of a log house may not show any discolouring at all after 15 years, while the sunny southern side may require retreating after only a couple of years. A high-quality opaque finish on a sawn timber surface should last for over 20 years. A translucent finish needs reapplying far more frequently than an opaque finish. One criterion for choosing your surface finish is, of course, how often you'll need to reapply it. A translucent finish is better for a smooth planed surface, as a film-free or thin-film surface is easier to take care of. In addition to appearance, both finishes have technical properties that may favour one option or the other. People often want to use a translucent finish to retain the solid timber feel of a log house, while a clapboard detached house is often finished using long-lasting, opaque house paints. Whether you choose a transparent or opaque finish is largely a matter of taste, or a question of the building's general style and appearance. In the Nordic countries, timber façades are usually made of coniferous species – spruce or pine – which are easy to treat in a variety of ways. Translucent or opaque – appearance and reapplication It can also be left completely untreated. A decorative wooden surface is often protected using a transparent varnish, wax, or oil. Things are different for interior surfaces – wood slowly changes its colour and appearance as it ages. If you don't want old-looking grey wood, then you will have to protect your timber. When designing a wooden building, you should decide how you want the exterior walls to look after five or 30 years. However, applying translucent finishes poses its own challenges.Īlthough many people want their wooden surfaces to retain a natural appearance, weathering should be taken into account when applying exterior finishes. A new generation of translucent coatings now exist alongside traditional exterior paints. Surface treatments improve the durability and appearance of timber surfaces, and also help a building to blend into its environment. Timber houses are a living cultural tradition in the Nordic countries. Translucent finishes alongside opaque paints
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