Woods to Know

Woods to Know: Red Gum

Red Gum (Liquidambar styraciflua)

by Peter MacSween

First of all, this article is not about the Australian Red Gum. Liquidambar styraciflua is native to North America and is also called Redgum, and to confuse things even further, it is also called Sweetgum, Sapgum and Satin Walnut. I'll keep things simple and just call it Red Gum from here on.

Red Gum is endemic to the southeastern United States. It is found growing from Connecticut to mid-state Florida and from Missouri to the Atlantic Coast  Populations are also found in Mexico and Central America. It is a fast growing tree and can produce dense stands that yield large amounts of timber. Within these areas, it is known for the sweet gum it produces when the bark is bruised.

Red Gum can grow to heights of 150 feet. Most trees will reach 100 feet with 2 to 3 foot diameters. The grain of the wood it produces is usually interlocked with a very fine uniform texture. The most distinguishing feature is the heartwood .  Typically, the heartwood is a reddish brown colour. With the best pieces, colours seem to swirl around producing an attractive and active presentation. Often there are black lines overlaid on top. This is a very distinctive look and one that made this wood very popular in the mid 1900s.

WTK_sweetgum


By contrast, the sapwood, often referred to as Sapgum, is a creamy white colour. Consequently, Sapgum can be stained and dyed to mimic more expensive woods such as cherry, walnut and mahogany.  The sapwood makes up a large percentage of the lumber produced by the tree whereas Red Gum can refer to lumber produced only from the heartwood of the Liquidambar styraciflua tree.

In its heyday, Red Gum was widely used for furniture, interior trim and millwork. It was used for core stock for panels as well as face veneer, boxes, woodenware, turnery and flooring. It was the favourite wood for the cases of radios and early television sets. Red Gum has been replaced by other species for may of these applications.  

The concern has always been that Red Gum is not stable. While valid initially, Red Gum deserves better. It responds well to an aggressive kiln drying schedule. The wood should be stickered on 12 inch centers and weighed down appropriately. Once dry, it can still move, but the resourceful woodworker can move the odds in his favour by careful preparation of the wood.

When you purchase Red Gum, it should be initially dressed over size. Let it acclimate inside to the final moisture content. A second dressing to the final dimensions should remove any warping. I would glue up any large panels at this stage. This should tame any of the problems with stability.

WTK_sweetgum_endgrain
Reg Gum end-grain

Red Gum works easily with sharp tooling. The grain is interlocked and can tear. Adjust your equipment for lighter cuts. Sandpaper should be sharp to handle areas of different densities. This wood glues, screws and nails well.  It responds well to all finishes even painting.

Canadian woodworkers should able to obtain Red Gum lumber at most specialty wood dealers. 4/4 is the most common thickness. The appearance of the heartwood is striking, perfect for panels. Price is usually dependant on appearance, with the most highly figured pieces commanding the best prices  Sapgum is a little harder to find. It tends to be the least expensive option.

This is a wood that should be more popular. It is not threatened, grows in large productive stands and can be managed for domestic consumption. Careful design, thoughtful management of the drying process and basic woodworking skills can bring this wood back into the shop of all craftspeople.


 
Average Dried Weight38 lbs/ft³A measure of its weight at 12% moisture and an ambient temperature of 70°F.
Specific Gravity.60A measure of the ratio of its density compared to water (at 12% MC)
ShrinkageRadial: 2.0%
Tangetial: 3.4%
Volumetric: 6.0%
 
Radial (the amount of crosswise shrinkage);
Tangential (the amount of lengthwise shrinkage);
Volumetric (the total amount of shrinkage.)
T/R Ratio1.7A measure of the uniformity of tangential to radial shrinkage.
Janka Hardness900 lbfA measure of resistance to denting and abrasion.
Crushing Strength5,790 lbf/in2A measure of compression strength parallel to the grain.
Colour
Color tends to be a golden to dark brown, sometimes with darker streaks. Sapwood is usually thin and yellow/white, clearly demarcated from the heartwood. Monkeypod is sometimes seen with highly figured curly or wild grain patterns.
GrainStraight, sometimes interlocked or wavy.
TextureMedium to coarse.
Workability
Generally easy to work with both hand and machine tools, though any interlocked grain may result in fuzzy or torn grain during planing operations. Glues and finishes well.
Uses
Veneer, plywood, millwork/trim, carving, cabinetry, furniture, musical instruments (guitars and ukuleles), and other small specialty wood items.
PriceContact your local dealer.
 
  
Photos and Specifications Courtesy of: The Wood Database