The sweet gum tree (Liquidambar styraciflua) is a common North American hardwood found throughout the eastern and southern United States. While the tree is recognizable by its star-shaped leaves and spiky seed pods, its lumber has two distinct trade names: sapgum and redgum. The wood’s appearance varies dramatically depending on whether it comes from the outer sapwood or the inner heartwood.
Distinctive Color and Appearance
The visual identity of sweet gum wood is defined by the stark difference between its sapwood and heartwood. The wide sapwood, marketed as “sapgum,” is typically a pale, uniform color, ranging from grayish-white to light pink or tan. This light color makes it suitable for applications where the wood will be painted or a consistent background is desired.
The heartwood, known as “redgum,” offers a richer, more varied aesthetic. Its coloring ranges from light reddish-brown to deep dark brown hues, sometimes resembling black cherry. Occasionally, the heartwood exhibits dark, irregular streaks of purple or black, sold as “figured redgum.”
The sapwood is highly susceptible to discoloration from chemical gray stain or blue stain fungi if not dried quickly. This susceptibility often leads to a splotchy appearance in commercially available lumber.
Grain Pattern and Texture
Sweet gum wood possesses a fine, uniform texture, with pores and annual growth rings inconspicuous to the naked eye. This structure allows the wood to be sanded to an exceptionally smooth finish, often resulting in a natural luster. The subtle sheen sometimes displayed has historically earned it the nickname “satin walnut.”
The grain itself is frequently interlocked, meaning the wood fibers spiral and reverse within the trunk. This interlocking grain is a defining characteristic that can cause significant tear-out when the wood is planed or machined. When quartersawn, this spiraling fiber direction is revealed as a striking ribbon-stripe figure, similar to the effect seen in some varieties of mahogany.
Physical Characteristics and Stability Issues
Sweet gum is classified as a moderately hard, intermediate weight hardwood. It has a Janka hardness rating of approximately 850 pound-force (lbf), similar to soft maple, making it reasonably resistant to denting for interior applications. Its density averages around 36 pounds per cubic foot at 12% moisture content.
The primary challenge is its pronounced instability and high shrinkage rate. The wood has a high volumetric shrinkage coefficient, comparable to red oak. This high degree of movement causes the lumber to warp, twist, and check severely during initial drying. Even after kiln-drying, the interlocked grain contributes to the wood moving considerably as its moisture content changes in service. Furthermore, the wood offers little natural resistance to decay, meaning it should not be used in outdoor or damp environments.
Primary Uses in Woodworking
Sweet gum wood is utilized across various woodworking and manufacturing sectors due to its moderate strength, fine texture, and attractive grain patterns. It is a common species used in the production of veneer and plywood, valued for its ability to be rotary-cut into thin sheets. The resulting veneer faces panels for furniture, cabinets, and decorative wall coverings.
The lumber is also frequently employed as a secondary wood in furniture construction, serving as core stock, drawer sides, or internal framing components. Because of its pale sapwood and uniform texture, it accepts stains exceptionally well, allowing manufacturers to mimic the appearance of more expensive woods. This staining capability makes it a popular, low-cost substitute for woods like walnut or cherry in applications such as interior trim and cabinetry.