Wood treated with SILRES® WH can in principle be painted, if some weathering of the impregnated substrate is allowed first. However, it is important to note that smooth wooden surfaces will absorb only some of the silicone – the rest remains on the surface. As a result, and especially in the case of highly concentrated wood preservatives, paint adhesion may be restricted and leveling impaired. For this reason, SILRES® WH should not be employed as a primer.
We tested SILRES® WH as it is (not combined with other products). The focus of our trials was the durability during weathering. The outdoor weathering showed very good visual beading and low water absorption after 17 years of natural exposure (video clip, trial with Karsten tubes). Mainly though, we use a QUV-B chamber and observe the impact of weathering on the beading effect (the weathered wooden stripes on our demo-tool for the ECS have been weathered in a chamber).
SILRES® WH maintains the wood breathability on a high level, meaning shrinkage and expansion will not be completely prevented. However, since the silicone resin is flexible it will not flake off due to shrinkage or expansion. Also the silicone resin reduces the amount of moisture absorbed and therefore keeps shrinkage and expansion at a lower level. This has a positive influence on the cracking tendency.
So far this has not been tested, but the reaction to fire will be examined in our labs. In this respect, it is important to note that silicone resins generally do have a high resistance to fire. They are, for instance, also used as binders in heat-resistant paints. The first positive feedback was given for the use of SILRES® WH in intumescent coating for wood.