Understanding Lumber Color Change - Part 2
As a natural building material, wood has earned its title as “The Ultimate Green Building Material.” But, of course, green is not the color of wood which most people want, and sometimes the color they do want is unrealistic.
Perhaps they’re trying to match a sun-bleached piece that’s been maturing for years (see Part 1). Or perhaps they’re a fan of that famous look of cherry furniture, but they don’t understand what it takes to achieve such a finish.
Unlike exterior species that experience change due to sunlight and other weather components, the unique natural coloring attributed to Cherry relies upon a chemical change that occurs over time but can be artificially achieved, as well.
Initial Color Change
Even when lumber is protected from punishment by sun, rain, and wind, it still changes color over time. In fact, you can often see a difference in color between a freshly cut or planed board and one that was milled hours or days ago.
When we apply some kind of finish, the effect is similar to what occurs when you simply wet the surface; however, the finishes react well after the finish has cured, continuing to alter the color of the wood.
When freshly milled, Cherry is typically a light pink color. When left to nature’s course, it usually deepens into a color that’s closer to brown than red. Stain or dye, along with an accumulation of dirt, is what actually creates the dark red coloring many people attribute to Cherry.
The attractive deep red coloring many associate with Cherry is often achieved today with a heavy dose of dye — whether the species underneath is actually Cherry or not.
Remember, though, that any kind of finish will continue to react to the wood, over time; consequently, as the color of the wood continues to change, the color that eventually emerges may be different than what you initially desired.
The chemical components of lumber are dependent not only on the species, but also on the soil chemistry of the trees from which they come. The components that make the most significant differences are Lignins and extractives, and those are highly present in Cherry wood.
Basically, Lignins are water-resistant compounds that work to bind the cellulose wood fibers; extractives are exotic compounds often extracted for use in Turpentine, Tannins used for wine and whiskey barrels, or a variety of pharmaceutical products.
While a tree is standing, Lignins and extractives cause the color change that allows sapwood to transform into heartwood. Later, they react with the longer wavelengths of light found inside homes by reacting and breaking down when exposed to heat and chemicals such as those used to treat and clean wood furnishings and floors.
If you sanded a centuries-old tabletop back to the never-exposed raw wood, those compounds would begin reacting with the air and light to begin the darkening process anew.
Continue reading with Part 3.