Koa

Koa (Acacia koa)

Common Name(s): Koa, Hawaiian Koa

Scientific Name: Acacia Koa

Distribution: Hawaii

Tree Size: 65-100 ft (20-30 m) tall, 3-5 ft (1-1.5 m) trunk diameter

Average Dried Weight: 42 lbs/ft³ (670 kg/m³)

Basic Specific Gravity: .53

Hardness: 1,110 lb_f (4,940 N)

Bending Strength: 11,230 lb_f/in² (77,420 kPa)

Elasticity: 1,570,000 lb_f/in² (10,830 MPa)

Shrinkage: Radial: 5.5%, Tangential: 6.2%, Volumetric: 11.7%, T/R Ratio: 1.1

Color/Appearance: Color can be highly variable, but tends to be medium golden or reddish brown, similar to Mahogany. There are usually contrasting bands of color in the growth rings, and it is not uncommon to see boards with ribbon-like streaks of color. Boards figured with wavy and/or curly grain are also not uncommon.

Grain/Pore: Koa has small, open pores and a medium to coarse texture. Grain is usually slightly interlocked, and sometimes wavy.

Durability: Rated as non-durable to perishable regarding decay resistance, Koa is also susceptible to termite attack.

Workability: In most circumstances, Koa is easy to work, and sands well. However, figured wood, or pieces with heavily interlocked grain can be difficult to plane or machine without tearing or chipping of the grain; also, Koa can occasionally give problems in gluing, though this is somewhat uncommon. Koa turns, stains, and finishes well.

Smell: There is no characteristic odor associated with this wood species.

Safety: There have been no adverse health effects associated with Koa. See the articles Wood Allergies and Toxicity and Wood Dust Safety for more information.

Price Range: With the tree endemic to Hawaii only, and with supplies dwindling, Koa is likely to be rather expensive. Also, boards of highly figured and/or curly Koa can command fantastic prices.

Comments: Although Koa is naturally quite abundant on the islands of Hawaii, most Koa forests have been cleared for grazing pastures; and since young Koa seedlings are edible for grazing animals, most new trees are prevented from growing to lumber-harvestable size. As a result, mature Koa trees are either scarce, or in hard-to-access mountainous locations, and the price of Koa is likely to only increase further in the future. Australian Blackwood (Acacia melanoxylon) is considered to be a more sustainable, and visually/mechanically similar substitute.

Koa is widely considered to be the most beautiful and useful of Hawaii’s native hardwoods, and along with Monkey Pod and Mango, it is the most common Hawaiian species to be imported into the lower 48 United States.

Visually, Koa has been compared to Mahogany, while in terms of working and mechanical properties, it has been compared to Walnut. Because of its nearly equal tangential and radial shrinkage, (its T/R Ratio is only 1.1), Koa tends to be quite stable regarding environmental changes in humidity.

Some common uses for Koa include: veneer, furniture, cabinetry, musical instruments (especially guitars and ukuleles), canoes, gunstocks, carvings, bowls, and other turned/specialty wood objects.