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