“Curly maple” describes a distinctive wood figure, not a separate species of maple tree. This unique pattern is characterized by a wavy, three-dimensional appearance that runs perpendicular to the length of the wood fibers. Often referred to as “fiddleback” due to its historic use in instrument making, the figure is prized by woodworkers for its shimmering effect. The phenomenon is a rare deviation from the typical growth pattern, which gives the wood an illusion of depth. Understanding the cause of this figure requires first establishing the structure of wood in a typical, straight-grained tree.
Understanding Normal Wood Structure
The structure of wood, or secondary xylem, is organized by the vascular cambium, a thin layer of cells situated beneath the bark. This cambial layer continuously divides, producing new xylem cells inward toward the center of the trunk. These cells form the wood tissue itself.
In a normal tree, the structural cells of the wood are aligned in an axial system, running parallel to the long axis of the trunk. This straight alignment is the default growth pattern, maximizing the tree’s strength and efficiency for water transport. The resulting grain appears uniform and straight along the length of the board. This standard structure serves as the baseline against which the “curly” figure is defined.
The Biological Origin of Wavy Grain
The formation of curly maple is rooted in a systematic disturbance within the cambium layer. Instead of generating cells that run straight up the trunk, the cambium in these areas begins to produce wood fibers that undulate in a continuous wave pattern. This deformation means the wood cells are repeatedly compressed and angled relative to the trunk axis, creating a permanent “washboard” effect through the entire thickness of the wood in that section.
The precise trigger for this consistent cellular wave remains a subject of scientific investigation, though two main hypotheses are accepted. The most compelling evidence points toward a strong genetic predisposition, suggesting that some maple trees are programmed to develop this figure. Studies involving the vegetative propagation of figured trees, such as sycamore maple, have shown that the wavy grain trait is stable and can be reliably inherited through cloning.
Environmental and mechanical stress also influence the pattern in certain trees. External forces, such as prolonged wind stress or the constant compression at the base of a tree, can physically distort the cambium layer. This mechanical pressure may force the developing wood cells to deviate from their straight path. However, the genetic factor appears to be the dominant cause for the widespread, consistent figure found throughout the length of the most valuable figured logs.
The Visual Effect of Shimmering Figure
The visual quality that defines curly maple is known as chatoyance, a term derived from the French for “cat’s eye,” which describes a shimmering, shifting optical effect. This effect is a direct result of the wavy fiber structure interacting with light. When wood is cut, the undulating fibers expose alternating faces and end-grain-like sections across the surface of the board.
When light hits the surface, it reflects differently depending on the orientation of the exposed fibers. At the crests of the waves, the fibers are angled in a way that reflects the light directly back toward the viewer, causing that section to appear bright. Conversely, in the troughs of the wave, the fibers are angled away, scattering the light and making those sections appear darker.
This rapid alternation of light-reflecting and light-scattering surfaces creates the illusion of a three-dimensional wave pattern. As the viewing angle or the light source shifts, the areas of brightness and darkness appear to move and interchange positions. This dynamic interplay of light gives curly maple its shimmering quality, making it a favorite for decorative and musical applications.