Color changing wood

That purpleheart plank that was the perfect shade of violet when you bought it suddenly displayed a dull gray cast after machining. But a few days after you set the nondescript board in the corner, the violet came back, more vibrant than before. Now several years after you used the board to make a jewelry box, you find the purple has faded to a drab brown. What happened?!?

Opinions vary on the exact reason some wood species change. But most experts agree that two main culprits speed color transformation: oxidation (exposure to air) and UV (ultraviolet light) exposure. The purpleheart plank encountered both. Over months and years, an exposed project will darken, lighten, or change colors, depending on the wood.

But you didn't get into woodworking so you could vacuum-seal your projects in a dark closet. Here's how you can slow, prepare for, or even use those color changes to your advantage.

Most film-building finishes slow—but don't halt—the oxidation process. Some expensive, marine-grade finishes contain UV inhibitors that will protect a project from the sun's harmful rays for a short time. Your best bet, though: Keep your projects out of direct sunlight.

Or to maintain your project's original color, design it for repeated resurfacing. Color changes tend to be shallow, and can be reversed by exposing the unaffected wood underneath. For example, the flat top of the tongue drum, below, takes a quick sanding and refinishing to reverse its age-browning.

Color changes enhance the appearance of some woods. Freshly exposed cherry starts as a salmon-pink color. But its true glamour derives from the rich copper tones earned with exposure to UV light. Similarly, mahogany's celebrated red-tinged brown comes with time. To hasten desired darkening, bathe the completed project in full sunlight. Rotate the piece regularly to evenly expose all parts. Within weeks, you will notice a significant color change.

Updating your kitchen-cabinet doors? Repairing an antique? Accelerating wood color change also helps when you're trying to match fresh wood to an older project. Dyes and stains might make pieces match for a short time, but eventually the natural color changes will alter them further. Again, use sunlight to bring the unfinished board closer to its final color before making the decision to add color. Generally, to varying degrees, bright woods will brown, light woods will darken, and dark woods will lighten with exposure.

To test their color-changing characteristics, we subjected 13 woods to nine months of sunlight and air—a "living room" test. Along with padauk and cherry, above, these three woods—mahogany, poplar, and purpleheart—showed the greatest amount of change. Many of the lighter-colored woods, such as oak, maple, and pine, proved more color-fast.