Wood of the Week: Purpleheart
Purpleheart, also widely known as amaranth or violet wood, has a wide growing range from Mexico to Central and South America. Some 20 different species of Peltogyne grow there. The species of greatest commercial use include Peltogyne paniculata, Peltogyne pubescens, Peltogyne porphyrocardia, Peltogyne venosa and Peltogyne densiflora. Prime growing areas for purpleheart are the Amazon region of Brazil as well as British, French and Dutch Guiana.
Common names include: Purpleheart, Palo morado (Mexico), Morado (Panama, Venezuela), Tananeo (Colombia), Koroboreli (Guyana), Purperhart (Surinam), Amarante (French Guiana), Pau roxo, Guarabu (Brazil), Violetwood (English trade).
The trees grow to heights of 170 ft with diameters to 4 ft, but usually 1.5 to 3 ft; boles are straight, cylindrical, and clear 60 to 90 ft above buttresses up to 12 ft. high. Commercially harvestable trees are from 150 to 300 years old. The sapwood is creamy white or off-white in color, and is very distinct from the heartwood. The color has also been described as pinkish cinnamon with light brown streaks, and is usually about 2 to 4 inches (5 to 10 cm) wide. The heartwood is initially dull brown, but it rapidly changes to a bright, vibrant purple. Prolonged exposure darkens the wood to a dark-purplish brown or dark brown, but the original color can be restored by recutting the wood. Color variation between boards is reported to be moderate to high. Presence of minerals in some boards may cause uneven coloration and steaming is reported to affect the color. Peltogyne timbers are reported to vary widely in color between, and probably within, species.
The texture of the wood is medium to fine; luster medium to high, variable; grain usually straight, sometimes wavy, roey, or irregular; without distinctive odor or taste.
Basic specific gravity is 0.67; with a weight around 50 to 66 pounds per cubic foot, depending on species.
Shrinkage green to ovendry is; radial 3.2%; tangential 6.1%; volumetric 9.9%.
Stability after manufacture or movement is rated as small.
Purpleheart is exported around the world as fine veneer and lumber. It is used for inlay, parquet and traditional flooring, overlay, architectural uses and fine furniture as well as for turnery and specialty items such as art objects, jewelry, picture frames and silverware handles. In the countries where it grows, the hard and heavy wood is also used for more utilitarian purposes due to its innate strength and unique properties.
It is moderately difficult to work with either hand or machine tools. It dulls cutters, and exudes a gummy resin when heated by dull tools resulting in scorching of the surface of the wood. Slow feed rates and carbide cutters are suggested. Purpleheart turns smoothly, with the wood coming off in small chips rather than curls. It holds screws and nails well, though predrilling is recommended to avoid splitting. It is easy to glue with all common wood glues.
Almost any finish works with Purpleheart, however the heartwood is somewhat resistant to impregnation with finishing oils, the sapwood is permeable. Some solvents can cause the color to bleed. Treatment against the effects of ultra-violet rays has been suggested to maintain the original color of the wood. At least one source reported that treatment with Armorall, the car finish product, under lacquer is reported to hold the color well. The use of a UV protecting Spar Varnish can preserve the color up to ten years.
The Heartwood is rated as highly durable in resistance to attack by decay fungi; very resistant to dry-wood termites; but little resistance to marine borers easy to glue, and takes finishes well.
Purpleheart is reported by some to be fairly difficult to sand, though in my experience with bowls and pens, it is not harder than any other South American hardwoods, and certainly not as problematic as the Rosewoods.
Purpleheart heartwood is reported to steam bends fairly well.