Comparing Honeylocust and Black Locust for Epoxy Builds
Choosing between Honeylocust and Black locust for a custom epoxy river table involves balancing raw strength against wood movement. While both trees share similar common names, their physical properties differ in ways that directly impact tabletop fabrication. Baseline performance data from the USDA Forest Products Laboratory Wood Handbook (FPL-GTR-282) provides clear metrics for evaluating how each species handles load, seasonal humidity swings, and long-term service.
Density, Weight, and Slab Handling
Both species produce dense, heavy hardwoods that yield substantial, premium-feeling tabletops. In green condition, Honeylocust has a specific gravity of 0.60, whereas green Black locust measures 0.66. At 12% moisture content, Black locust reaches a specific gravity of 0.69. This density gives both woods significant mass, requiring sturdy table bases and careful joint reinforcement where wood interfaces with cured epoxy resin.
Dent Resistance: Side Hardness and Compression
Dent resistance determines how well a dining table or desk resists daily wear, dropped objects, and heavy use. Side hardness and compression perpendicular to the grain highlight clear differences:
- Side Hardness: Green Honeylocust tests at 1,390 lbf. Green Black locust tests at 1,570 lbf, increasing to 1,700 lbf at 12% moisture content. Both species offer high resistance to surface marring.
- Compression Perpendicular to Grain: Green Honeylocust measures 1,150 lbf/in², while green Black locust measures 1,160 lbf/in². At 12% moisture content, Black locust climbs to 1,830 lbf/in², showing exceptional resistance to localized crushing under heavy table legs or clamped hardware.
Stiffness and Strength for Spans and Overhangs
Large dining tables often feature unsupported spans and cantilevered edge overhangs. Structural deflection and bending limits are defined by the modulus of elasticity (stiffness) and modulus of rupture (bending strength).
For green lumber, Honeylocust demonstrates a modulus of rupture of 10,200 lbf/in² and a modulus of elasticity of 1.29 million lbf/in². By comparison, green Black locust provides a modulus of rupture of 13,800 lbf/in² and a modulus of elasticity of 1.85 million lbf/in². When dried to 12% moisture content, Black locust achieves a modulus of rupture of 19,400 lbf/in² and a stiffness modulus of 2.05 million lbf/in². The higher stiffness of Black locust allows for thinner tops across wide spans with reduced risk of sagging.
Seasonal Wood Movement and Shrinkage
Because cured epoxy does not shrink or swell with atmospheric humidity, controlling wood movement along the epoxy bondline is essential to prevent joint failure.
Honeylocust exhibits total green-to-ovendry shrinkage of 4.2% radially and 6.6% tangentially, with a volumetric shrinkage of 10.8%. Black locust shows total green-to-ovendry shrinkage of 4.6% radially and 7.2% tangentially, with a volumetric shrinkage of 10.2%. For small humidity changes in service, the dimensional change coefficients show that Honeylocust moves slightly less per percentage change in moisture content (0.00144 radial and 0.00230 tangential) compared to Black locust (0.00158 radial and 0.00252 tangential).
Both species share an identical calculated tangential-to-radial (T/R) shrinkage ratio of 1.6. A ratio of 1.6 indicates balanced shrinkage behavior across both axes, reducing internal stress, cup, and twist as ambient moisture fluctuates around the epoxy cast.
Decay Resistance and Moisture Content
Specific green moisture content percentages are not published for these species in the handbook tables, though both must be thoroughly dried before casting. In terms of natural durability, the USDA classifies Honeylocust heartwood as moderately resistant to decay, while Black locust heartwood is classified as very resistant. While indoor tables are rarely exposed to outdoor decay organisms, high natural decay resistance can be advantageous for covered patio tables or moisture-prone spaces.
Figures from the USDA Wood Handbook (FPL-GTR-282), Tables 4-1, 4-3, 5-3b, 13-5 and 14-1. Clear, straight-grained specimens; real slabs vary.
| Property | Honeylocust | Black locust |
|---|---|---|
| Specific gravity (12% MC) | — | 0.69 |
| Side hardness, lbf (12% MC) | — | 1,700 |
| Modulus of rupture, lbf/in² (12% MC) | — | 19,400 |
| Modulus of elasticity, million lbf/in² (12% MC) | — | 2.05 |
| Compression perpendicular to grain, lbf/in² (12% MC) | — | 1,830 |
| Radial shrinkage, green to ovendry (%) | 4.2 | 4.6 |
| Tangential shrinkage, green to ovendry (%) | 6.6 | 7.2 |
| Volumetric shrinkage, green to ovendry (%) | 10.8 | 10.2 |
| Dimensional change coefficient, tangential (per 1% MC) | 0.00230 | 0.00252 |
| Dimensional change coefficient, radial (per 1% MC) | 0.00144 | 0.00158 |
| Tangential/radial shrinkage ratio (calculated) | 1.6 | 1.6 |
| Heartwood decay resistance (Table 14-1) | Moderately resistant | Very resistant |
Which to Pick When
Select Honeylocust when you want lower dimensional change coefficients (0.00230 tangential versus 0.00252 for Black locust), which reduces stress along long epoxy seams in rooms with minor humidity fluctuations. Its 1,390 lbf green hardness provides more than enough surface durability for general home furniture.
Select Black locust when maximum stiffness and surface toughness are the priority. With a dry side hardness of 1,700 lbf, a modulus of elasticity of 2.05 million lbf/in², and a very resistant heartwood rating, Black locust excels on wide unsupported spans, high-traffic commercial tabletops, and projects demanding extreme scratch resistance. For either timber, ensure the slabs are properly dried and sealed according to your resin manufacturer’s technical data sheet.
Sources
Published October 28, 2026. Sources are linked in the text.
Header image: original graphic by BigEpoxy.com.
Staff note: In addition to bending strength, shear strength parallel to the grain is an important design consideration along deep epoxy river channels. Dry Black locust achieves a shear strength of 2,480 lbf/in² (and 1,760 lbf/in² green), compared to 1,660 lbf/in² for green Honeylocust, providing higher resistance to lateral stress along deep mechanical fasteners. (Source: USDA Forest Products Laboratory, Wood Handbook (FPL-GTR-282, 2021).)