Paints and solid-color stains with 100 percent acrylic resins are best able to provide the desired flexibility to withstand the expansion of contraction of the siding. With few exceptions, wood species play a lesser role in paint or stain performance. Western red cedar and pine, for example, both hold stain well because of the inherent chemical nature of the stain or paint product. However, woodcuts are a different story. This cut is less stable and is best used as rustic siding, rough side out.
Knots present a different problem.
Smooth, edge-grained wood, sometimes called quartersawn, holds stain and paint very well. This wood is very stable in comparison to flat-grained wood. Smooth western red cedar at one point in the past may have been sold with a condition referred to as mill glaze. It was reported that mill glaze interfered with good adhesion, but Cabot never experienced this with our Problem-Solver Oil Primer as a first coat. The heartwood of the tree, the darker center of the tree, is more resistant to attack by fungus, bacteria and certain critters.