The reason for this is that dark colours absorb significant levels of heat from the sun – and can essentially “cook” the weatherboard cladding. Excessive heat will exacerbate timber movement and increase the possibility of resin bleed, a common problem with radiata pine weatherboards.
Timber is a natural product. Resins are found in many types of softwood – and in particular New Zealand Radiata Pine. When the core temperature of timber cladding increases, pine resins can become mobile and can leach through the paint coating, creating an unsightly mess. This problem can affect new weatherboards- normally resulting in a distraught new home owner! Once resin bleed occurs, it can continue leaching from the wood for up to 2 years, requiring scraping , cleaning, re-sanding and re-painting.
It is documented that oil based primers and careful timber grading can reduce the possibility of resin bleed, but these solutions are far from comprehensive. Most timber weatherboards in New Zealand and Australia are preservative treated with solvent based wood preservatives (LOSP) which are also thought to mobilise pine resins.
Fortunately your friends at Abodo have a better solution: thermal modification.
The thermal modification process used for products like Vulcan Cladding drives resins and extractives from pine – at temperatures of up to 220 degrees. Like a well-worn pair of jeans, the resultant timber simply has nothing left to leach. The extremely high temperatures essentially fossilise the wood, increasing its stability.
Vulcan Cladding is therefore more suitable for darker colours than standard pine.