Working with Alumbi in Wood and Epoxy Tabletops
Alumbi (Julbernardia seretii) is an African hardwood belonging to the Leguminosae family. Documented in the CIRAD Tropix technical sheet, Alumbi is recognized in fine woodworking for applications such as cabinetwork, high-class furniture, flooring, and interior joinery. For epoxy table makers, Alumbi offers attractive coloration, high stiffness, and clean machining, though its stability and natural durability require specific shop practices to ensure a lasting resin bond.
| Property | CIRAD Tropix value | What it means / US units |
|---|---|---|
| Botanical name(s) | Julbernardia seretii | |
| Colour / texture / grain | Red brown; texture fine; grain straight to entangled; interlocked grain slight | |
| Specific gravity (12% MC) | 0.74 | about 46.2 lb/ft³; a 2-inch-thick slab weighs about 7.7 lb per sq ft |
| Monnin hardness (12% MC) | 4.5 | French hardness scale; higher = harder (not a Janka value) |
| Total tangential shrinkage | 7.9 % | green to oven-dry |
| Total radial shrinkage | 4.4 % | green to oven-dry |
| Ratio St/Sr | 1.8 | closer to 1 = less cupping tendency |
| Coefficient of volumetric shrinkage | 0.45 % per % MC | volume change per 1% change in moisture content |
| Fibre saturation point | 29 % | |
| Thermal conductivity | 0.24 W/(m·K) | |
| Crushing strength (12% MC) | 67 MPa | about 9,720 psi |
| Static bending strength (12% MC) | 109 MPa | about 15,810 psi |
| Modulus of elasticity (12% MC) | 18,060 MPa | about 2,619,000 psi |
| Decay (fungi) resistance | Durability class 4 – poorly durable | |
| Termite resistance | Class S – susceptible | |
| Dry-wood borer resistance | Class S – susceptible (risk in all the wood) | |
| Heartwood treatability | Class 3-4 – poorly or not permeable | |
| Use class from natural durability | Class 2 – inside or under cover (dampness possible) | |
| Drying | rate normal; distortion: slight risk; checking: slight risk; collapse: no known specific risk; casehardening: no known specific risk | |
| Suggested kiln program temperatures | 53–65 °C | about 127–149 °F |
| Machining | blunting normal; saw teeth: ordinary or alloy steel; cutting tools: ordinary | |
| Nailing and screwing | Good | |
| CITES status | This species is not listed in the CITES Appendices (Washington Convention 2025). |
Values from the CIRAD Tropix technical sheet (average values for mature wood, 12% moisture content where noted). US-unit conversions are calculated by BigEpoxy (1 MPa = 145.04 psi; density = specific gravity × 62.43 lb/ft³).
Pros and Cons of Alumbi for Epoxy Tables
Pros
- Appealing figure: Heartwood displays a rich red-brown tone, often accented with brown or yellow stripes.
- Striking live edges: Yellow sapwood is clearly demarcated from the heartwood, providing high visual contrast along an epoxy river edge.
- Exceptional finish quality: Alumbi features a fine texture and leaves a very fine surface after sanding.
- Manageable tooling requirements: Tool blunting is normal, allowing woodworkers to cut and shape slabs using ordinary cutting tools and ordinary or alloy steel saw teeth.
- High stiffness: A modulus of elasticity of 18,060 MPa (about 2,619,000 psi) gives tabletops strong structural rigidity.
- Regulatory freedom: The species is not listed in the CITES Appendices (Washington Convention 2025).
Cons
- Poor natural decay resistance: Classified as Durability class 4 (poorly durable) against fungi, making it unsuitable for exterior tables or damp outdoor environments.
- Insect susceptibility: Heartwood and sapwood are rated Class S (susceptible) to termites and dry-wood borers.
- Low permeability: Heartwood treatability is rated Class 3-4 (poorly or not permeable), meaning preservative treatments do not penetrate deeply.
- Moderate shrinkage differential: With a tangential shrinkage of 7.9% and a radial shrinkage of 4.4% (ratio of 1.8), boards require careful moisture equilibration before casting with epoxy.
- Interior limitation: Natural durability places Alumbi squarely in Use Class 2 (strictly for interior environments or under cover).
Slab Selection and Log Dimensions
According to CIRAD Tropix data, Alumbi logs typically range from 80 to 90 cm in diameter. This provides ample width for wide furniture components, river table halves, or full-width bookmatched conference tables. When evaluating raw slabs, pay attention to the sapwood layer, which ranges from 5 to 15 cm in thickness. The sapwood is a distinct yellow that stands out against the red-brown heartwood. Grain patterns vary from straight to entangled, with slight interlocked grain that adds subtle visual character to the slab surface.
Density, Weight, and Hardness
Alumbi is a moderately heavy timber with a specific gravity of 0.74 at 12% moisture content. In the shop, this translates to an air-dry density of approximately 46.2 lb/ft³, meaning a 2-inch-thick slab weighs roughly 7.7 lb per square foot. Builders should plan for sturdy table legs and robust joinery to support larger builds.
The wood has a Monnin hardness rating of 4.5 at 12% moisture content. The Monnin scale is an established French testing method where higher numbers indicate harder timber. It must not be confused with or converted to Janka hardness values. A Monnin value of 4.5 reflects solid surface hardness that resists everyday indentation well, aligning with its standard commercial use in flooring and indoor staircases.
Drying Behavior and Stability Next to Epoxy
Epoxy resin cures into a rigid plastic that does not expand or contract with humidity. As a result, the dimensional stability of the embedded wood slabs dictates whether an epoxy river joint remains tight over time. Alumbi exhibits a total tangential shrinkage of 7.9% and a total radial shrinkage of 4.4%, resulting in a tangential-to-radial shrinkage ratio of 1.8. Its coefficient of volumetric shrinkage is 0.45% per 1% change in moisture content, with a fiber saturation point of 29%.
Because the tangential movement is nearly double the radial movement, quartersawn or rift-sawn boards offer greater dimensional stability next to a cured epoxy river than flatsawn slabs. The CIRAD Tropix data reports that Alumbi has a normal drying rate with only a slight risk of distortion and checking, and no known specific risk of collapse or casehardening. Suggested kiln programs dry the lumber at temperatures between 53 °C and 65 °C (approximately 127 °F to 149 °F). Ensure your timber is fully stabilized to indoor equilibrium moisture content before pouring resin.
Machining, Sealing, and Finishing
Alumbi performs reliably under standard woodworking equipment. The blunting effect on cutters is normal, meaning standard high-speed steel or carbide tooling handles shaping and flattening effectively. Nailing and screwing properties are rated as good, ensuring strong mechanical attachment to table base plates.
The wood produces a very fine surface after sanding. However, because heartwood treatability is rated Class 3-4 (poorly or not permeable), deep penetration of liquid sealers into dense heartwood fibers is limited. Before pouring a deep resin river, apply a thin seal coat of epoxy across all live edges and end-grain surfaces to block air displacement and prevent bubbles from bleeding into the casting resin. Keep finished Alumbi river tables strictly indoors in climate-controlled spaces, consistent with its Use Class 2 rating.
Sources
Published October 31, 2026. Sources are linked in the text.
Header image: original graphic by BigEpoxy.com.
Staff note: When inspecting live edges on Alumbi slabs, check the 5 to 15 cm wide yellow sapwood thoroughly for insect exit holes before casting, as CIRAD classifies the species as Class S (susceptible) to dry-wood borers across all of the wood. (Source: CIRAD Tropix 7 technical sheet: Alumbi.)