Timber iQ April - May 2018 // Issue: 37 | Page 44

FEATURES Surfaces that aren’t prepared well can, overtime, peel or crack. Continued from page 40 and hard. They also do not contain ultra-violet (UV) absorbers and other additives necessary in outdoor products. Outdoor products are formulated to dry slower (as they must remain flexible for longer periods to be able to survive the large temperature fluctuations that outdoor wood is subject to). This means that they will tend to remain slightly soft and ‘sticky’ if used indoors. They also contain a multitude of additives required for their survival in outdoor conditions which make them a little more expensive than indoor products,” he says. “Interior wood furniture coatings have a refined smooth finish and are formulated to withstand everyday bumps and knocks, products such as toothpaste, makeup, condiments, alcohol spillage and so on. Exterior coatings on the other hand need to withstand the natural elements of wind, sun, rain, hail and airborne contaminants amongst other things,” explains John Wanliss, MD of WoodGlass Coatings. He shares that quality water based exterior coatings offer flexibility and are non-yellowing. “Wood is sensitive to photochemical degradation and preventing ultra violet light from penetrating the timber surface therefore destroying the lignin is the major challenge for the paint chemist. All good quality exterior coatings contain one or more additives to filter and absorb harmful UV radiation.” 42 APRIL / MAY 2018 // Wanlis advises the following three-tier approach to combat the effects of UV, recommended by research and development laboratories, ICA Group: 1. A water-based, coloured, impregnating sealer is applied to the prepared timber. This deep penetrating sealer enhances the timber colour as it contains semi- transparent oxide pigments. The pigments absorb UV and, together with subsequent coats, limit the effect of UV radiation on the wood. 2. A water-based sealer is applied next, which is either a clear coat or may have a translucent colour. A good quality clear sealer will contain UV absorbers and light stabilisers while the coloured type typically contains a UV absorber and transparent pigments. 3. The final coat will be clear or translucent and contain UV absorbers and transparent pigments. This multilayer approach offers superior timber protection against the elements including UV radiation. APPLICATION AND TREATMENT When it comes to putting paint to wood, a basic understanding on how to apply a coating with a brush is all you need. Greeff states that there are many short videos on the internet that show the correct technique. Woodoc provides training to DIY timber enthusiasts while the South See more on page 44