Many softwoods naturally contain resins. These resins are composed mainly of terpenes and derivatives, and are an essential part of the tree.
Resins contain antimicrobial properties that help prevent decay and fungal infections, and resins also decrease water loss during droughts or plant injury.
Resins are not so useful when softwood timbers are used in exterior applications. Resin persists in wood (such as pine) even after a tree is cut down. When exposed to heat, resins can mobilise – leaving a sticky mess exuding from exterior weatherboards, cladding timbers and decking.
Resins can bleed through coatings, and in many instances “resin bleed” can be a major issue for homeowners to contend with. The resin can be scraped off and the surface sanded and recoated, but resin bleed may continue bleeding throughout the life of the timber.
For this reason, many manufacturers of natural timber weatherboards and cladding specify that only lighter colours can be used on their products. This is to reduce the heat build up in the wood, and reduce the chance of resin bleed, and other resin related stains.
This fact is recognised in Australian and New Zealand building standards, and recommendations:
The Australian/New Zealand Standard, AS/NZS 2311:2009 Guide to the Painting of Buildings in section 2.2.5(i) states that "Dark Colours in exterior situations increase the absorption of heat and this may have a deleterious effect on the paint coatings and substrate materials".
BRANZ, New Zealand’s building advice organisation published a "Good practice guide" to "Exterior Coatings" and in section 4.2.2 recommends that "Colours are selected carefully to suit and minimise stress on the substrate".
Abodo’s Vulcan Cladding however, is a an excellent choice to mitigate resin bleed. In the thermal modification process most of the natural resins are burnt from the wood, meaning they are no longer there to bleed out. Using Vulcan Cladding allows homeowners the choice of a larger range of colours, and combined with Resene Coolcolour paints, even darker tones can be used.
Contact the Abodo team for more information on Vulcan Clading and darker colour paints and stains.