Technical Specification

Technical and certification information about Black Locust.

Black Locust is a very hard and strong wood, competing with Hickory (Carya genus) as the strongest and stiffest domestic timber, but with more stability and rot-resistance. Although it shares a similar name with Honey Locust, the two aren’t in the same genus, (Robinia and Gleditsia, respectively). Black Locust is heavier, harder, and has more of a green or yellow tinge, while Honey Locust tends to have a warmer orange or red tint.

​ Grade Guide

Black Locust Characteristics

Like all species of wood, Black Locust is not a “man-made” product. The complex mix of characteristics that distinguish one sample of wood can be determined by the genetics of the species. Soil type and climate influence the composition of each individual tree; therefore slight variation in color, grain structure, density and general appearance can contribute to the character and visual interest of Black Locust.

As Black Locust weathers, it develops a silvery-gray patina. The color is a result of natural weathering: U.V. rays, rain, snow and oxygen. There is not a known finish to eliminate U.V. deterioration for Black Locust or other wood species, U.V. wood treatments will only delay the natural patina of the wood. One of Black Locust’s distinct characteristics is its ability to accept stain or paint. In contrast, tropical hardwoods are unable to sustain a different color range due to their oily composition.

Premium Grade

The lumber comes from the “Best of the Best” Black Locust grown in the Appalachian Mountains. Each individual piece is carefully inspected to ensure premiere quality, durability and appearance. Visually, Black Locust is known for its knots, mineral streaks, checks and bark insertions. To ensure superior appearances, only the most appealing pieces qualify as Premium Grade. Sound included knots, 3″ in diameter and less, minor mineral streaks and small bark insertions are admitted to highlight characteristics of the Black Locust species. Checks less than 1/12th of the board length are also admitted.

No. 1 Grade

The lumber comes from Black Locust grown in the Appalachian Mountains. Each individual piece is carefully inspected to ensure quality and durability. Visually, Black Locust is known for its knots, mineral streaks, checks and bark insertions. All sound knots are admitted in this grade. All other characteristics that do not affect the durability of this product are also admitted — surface checks, mineral streaks, bark insertions and grub holes. A popular product, without the premiere price.

Technical Specification List

Common Name(s):
Black Locust, Robinia, False Acacia

 

Scientific Name:
Robinia pseudoacacia

 

Distribution:
Central-eastern United States (also widely naturalized in many temperate areas worldwide)


Tree Size:
65-100 ft (20-30 m) tall, 2-3 ft (.6-1 m) trunk diameter


Average Dried Weight:
48 lbs/ft3 (770 kg/m3)


Specific Gravity (Basic, 12% MC):
.66, .77


Janka Hardness:
1,700 lbf (7,560 N)


Modulus of Rupture:
19,400 lbf/in2 (133.8 MPa)


Elastic Modulus:
2,050,000 lbf/in2 (14.14 GPa)


Crushing Strength:
10,200 lbf/in2 (70.3 MPa)


Shrinkage:
Radial:4.6%
Tangential: 7.2%
Volumetric: 10.2%
T/R Ratio: 1.6


Color/Appearance:
Color can range from a pale greenish-yellow to a darker brown. Tends to darken to a russet brown with age. Can be confused with Osage Orange and Honey Locust in some instances.


Grain/Texture:
Grain is usually straight, with a medium texture.


Endgrain:
Ring-porous; large earlywood pores 2-3 pores wide, small latewood pores in clusters and tangential bands; tyloses extremely abundant; growth rings distinct; narrow to medium rays barely visible without lens, spacing normal; parenchyma vasicentric, lozenge, and confluent.


Rot Resistance:
Rated as very durable in regards to decay resistance, with good weathering characteristics. Frequently used as fence posts for its outdoor longevity.


Workability:
Overall working characteristics for Black Locust are mixed: although the grain is usually straight, its high density and hardness can make it difficult to machine. Black Locust also has a moderate blunting effect on cutting edges. Responds very well to both lathe turning and steam bending; glues and finishes well.


Odor:
No characteristic odor.


Allergies/Toxicity:
Although severe reactions are quite uncommon, Black Locust has been reported to cause eye and skin irritation. Another (uncommon) side effect reported is nausea. See the articles Wood Allergies and Toxicity and Wood Dust Safety for more information.


Pricing/Availability:
Black Locust prices can vary depending on location, but prices should be moderate within its natural range. Those living in the eastern United States can expect prices to be comparable to White Oak. In other areas where the lumber has been imported, the prices can be much higher.


Sustainability:
This wood species is not listed in the CITES Appendices, and is reported by the IUCN as being a species of least concern.


FSC®:
We are a certified source of Black Locust worldwide. Please contact us for FSC® certified products.


View Our FSC® Certification

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