The color-changing process of decking lumber is usually tied to sun exposure; however, one decking species tends to experience color change beyond the typical graying that all lumber species undergo over time when exposed to the elements. Teak decking reacts the way it does for the same basic reasons that interior species such as Cherry and Mahogany react: chemical components called extracts and lignins. So let’s take a look at what these components are and how they affect certain lumber species.
Lignins and extractives are the chemical components that make the most significant difference when it comes to color change. The water-resistant components called lignins provide binding of cellulose wood fibers, while the exotic compounds referred to as extractives are often known for their use in pharmaceutical products as well as Turpentine. In a living tree, these chemical components produce color change in sapwood when it’s converted into heartwood. Once milled and installed, they continue to react to longer wavelengths of light that are found indoors; when they come into contact with either heat or chemicals such as laquers, varnishes, and furniture waxes, they break down. These chemical reactions continue to occur throughout the lifespan of the wood, serving to darken or deepen its color.
While the chemical changes described above certainly occur indoors, they can also be exacerbated when directly exposed to the sun. Even still, addition of finishes typically intensifies the natural color of any lumber species. The famous “cherry finish” coveted by many is far from the natural light pink hue of freshly milled Cherry. The rich, dark, reddish brown color many associate with Cherry is actually a result of stain combined with years of accumulated dirt. (Too bad no one asks for a dirt finish!) To accommodate customer requests and meet their expectations, many furniture makers heavily apply dye to create a “Cherry finish” with a variety of lumber species; if they do actually use Cherry lumber, the chemical reaction might eventually create a color that’s far darker than desired.
Teak Color Change
Though the chemical components of Teak are similar to those of Cherry and Mahogany, the results are quite distinct. Teak contains a high degree of two extractives: oil and silica. These components make it a fabulously weather-resistant species suitable not only for exterior applications such as decking but also for marine applications. Freshly-milled Teak emerges from the planer with a streaky, sometimes rainbow-colored appearance that no one would want to see on a high-end project. Over time and with sun exposure, the colors mellow into the honey brown color typically associated with the species.
While we can understand the basic chemical reactions and adjust expectations accordingly, in the end we need to remember that wood is an organic material, and as such, each board is truly unique. The measure of unpredictability that comes with that fact is part of wood's allure and also part of its enduring beauty.