The effect of 6 month outdoor weathering on the resistance of acrylate paint systems on different types of pine and spruce sapwood to mould fungi was studied. Dipping into the preservative prior to painting, a primer with and without a fungicide (propiconazole + IPBC 0.50 + 0.2%) and a topcoat with and without a fungicide (propiconazole + IPBC 0.25 + 0.12%) were combinations of the treatments studied. Weathering decreased ability of the fungicides to protect the paint films. The kiln-dried yellow nutrient rich surfaces of the pine and spruce sapwood were more susceptible to growth of bluestain and mould fungi than the spruce surface sawn 10 mm below the original kiln-dried surface. The most effective treatment combinations on the resawn spruce material were able to give a sufficient protection against bluestain and mould after outdoor weathering and subsequent 23 weeks incubation at RH 100%. However, the effect was markedly lower on the kiln-dried surfaces of pine and spruce sapwood. On the samples without the fungicide, decay was also found. The study is a part of a project CT94-2463 in the AIR programme of DG XII.

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