The timeless beauty of natural wood certainly makes up for its sometimes unpredictable nature. (Hey, we all need a little excitement now and then, right?) Usually, though, someone who knows lumber can predict how it will behave in various circumstances. From movement to color variation, these things are pretty much an exact science. At the same time, though, they can’t necessarily be controlled. We think this adds, rather than detracts, from the allure of real wood.
As you understand the process of color changing, you’ll be more likely to appreciate the appearance of time-worn wood as well as how to prevent it — or even restore it — if you so desire.
Why Lumber Changes Color
Not only does wood fade when exposed to sunlight, but some species also experience chemical changes. Those two reasons combine to make matching new wood to an existing wood structure somewhere between difficult and impossible. (If the existing structure is outdoors, then count on the request landing in the realm of “impossible.”)
Over time, though, if the new wood is left untreated, it will fade into a gray patina that will match the older structure. This silvery gray can, however, be given a new life if the outer layer is cut, sanded, or planed to reveal a layer of wood that has not yet been exposed to the elements.
Differences in How Various Species Change
While all wood species will “go gray” at some point (assuming they are not specially treated to prevent that process), not all species will change at the same rate. Many tropical wood species, in particular, fight the process for much longer, because of their higher levels of oil content. Basically, the graying is caused by the sun’s bleaching and drying, so any oil or resin will help the wood resist that process.
You can artificially help prevent bleaching by adding oil to the surface as a matter of maintenance. (Consider this fact when you throw around phrases like “maintenance-free decking.” All wood requires some maintenance if you want to keep it from going gray.) You’ll want to keep in mind that since it is drying that causes the color change, you’ll also notice checks, or surface cracks, as the color shifts.
Speeding Up the Natural Process
Some people simply don’t want to wait for Nature to take its course and bleach the new lumber to match the older stuff. As a result, bleaching oils are on the market and claim to speed things up a bit. However, if you try them, you’ll likely discover that they don’t have quite the same effect as natural weathering does. The inimitable combination of UV light, longer wavelength light, heat, wind, and water just can’t be replaced with a chemical bleach.
Bleaching isn’t the only way wood changes color over time. Head over to our next post to find out more.
Read the Series
• Wood Color Change, Part 1
• Wood Color Change, Part 2
• Wood Color Change, Part 3
