Keranji as a Tabletop Timber
Keranji encompasses several species from the genus Dialium native to Asia-Oceania, primarily including Dialium cochinchinensis, Dialium indum, and Dialium platysepalum. Recognized for its exceptional density and structural strength, this hardwood is traditionally utilized in industrial flooring, heavy carpentry, vehicle flooring, and tool handles. For custom furniture builders designing epoxy river tables, Keranji presents distinct visual character alongside technical challenges regarding weight, moisture movement, and bonding.
According to technical data published in the CIRAD Tropix technical sheet, Keranji heartwood exhibits a yellow-brown to gold-brown coloration that darkens over time, accented by lustrous stripes, yellow/brown deposits within the vessels, and a fine silver figure that produces subtle horizontal striping. The sapwood is clearly demarcated, white to yellowish, with a thickness ranging between 3 to 8 cm. Log diameters typically span 50 to 90 cm, offering moderate potential for live-edge slabs or wider dimensional boards.
| Property | CIRAD Tropix value | What it means / US units |
|---|---|---|
| Botanical name(s) | Dialium cochinchinensis, Dialium indum, Dialium platysepalum, Dialium p.p. | |
| Colour / texture / grain | Yellow brown; texture medium; grain straight to entangled; interlocked grain slight | |
| Specific gravity (12% MC) | 1.05 | about 65.6 lb/ft³; a 2-inch-thick slab weighs about 10.9 lb per sq ft |
| Monnin hardness (12% MC) | 12.3 | French hardness scale; higher = harder (not a Janka value) |
| Total tangential shrinkage | 6.6 % | green to oven-dry |
| Total radial shrinkage | 3.7 % | green to oven-dry |
| Ratio St/Sr | 1.8 | closer to 1 = less cupping tendency |
| Coefficient of volumetric shrinkage | 0.63 % per % MC | volume change per 1% change in moisture content |
| Fibre saturation point | 24 % | |
| Thermal conductivity | 0.33 W/(m·K) | |
| Crushing strength (12% MC) | 103 MPa | about 14,940 psi |
| Static bending strength (12% MC) | 197 MPa | about 28,570 psi |
| Modulus of elasticity (12% MC) | 28,460 MPa | about 4,128,000 psi |
| Decay (fungi) resistance | Durability class 3 – moderately durable | |
| Termite resistance | Class M – moderately durable | |
| Dry-wood borer resistance | Class S – susceptible (risk in all the wood) | |
| Heartwood treatability | Class 3 – poorly permeable | |
| Use class from natural durability | Class 2 – inside or under cover (dampness possible) | |
| Drying | rate normal to slow; distortion: high risk; checking: high risk; collapse: no known specific risk; casehardening: no known specific risk | |
| Suggested kiln program temperatures | 45–65 °C | about 113–149 °F |
| Machining | blunting normal; saw teeth: stellite-tipped; cutting tools: tungsten carbide | |
| Nailing and screwing | Good but pre-boring necessary | |
| 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).
Density, Hardness, and Structural Behavior
Keranji is an exceptionally heavy timber, featuring an average specific gravity of 1.05 at 12% moisture content. In practical terms, this equals approximately 65.6 lb/ft³, with a 2-inch-thick tabletop slab weighing roughly 10.9 lb per square foot before resin is added. Substructures, leg attachments, and bases must be engineered to support substantial dead loads.
On the French Monnin hardness scale, Keranji rates at 12.3. The Monnin test evaluates indentation resistance, where higher numbers indicate harder surfaces. Unlike North American Janka values, Monnin readings reflect a distinct standardized test and should never be translated into Janka figures. A rating of 12.3 signifies intense surface hardness and high crush resistance, matching its measured crushing strength of 103 MPa (about 14,940 psi) and static bending strength of 197 MPa (about 28,570 psi).
Dimensional Stability Around Epoxy Pours
When locking timber to a rigid epoxy core, understanding moisture-related shrinkage is essential. Keranji exhibits a total tangential shrinkage of 6.6% and a total radial shrinkage of 3.7% from green to oven-dry conditions. Its tangential-to-radial ratio (St/Sr) is 1.8, while its coefficient of volumetric shrinkage is 0.63% per 1% change in moisture content. The fiber saturation point sits at 24%.
Because the volumetric shrinkage rate is relatively high, Keranji will exert substantial force against an epoxy bond line if the surrounding environment experiences significant shifts in relative humidity. Slabs must be thoroughly acclimated and dried down to interior equilibrium moisture content before any resin is poured. CIRAD notes that Keranji carries a normal to slow drying rate, accompanied by a high risk of distortion and a high risk of checking, though it shows no known specific risk for collapse or casehardening. Recommended kiln schedules suggest temperatures spanning 45 to 65 °C (about 113 to 149 °F).
Machining and Epoxy Bonding Considerations
Despite its extreme density, the blunting effect on tools is rated as normal. However, CIRAD recommends utilizing stellite-tipped saw teeth and tungsten carbide cutting knives. Straight grain to entangled grain with slight interlocking can complicate flattening or planing operations, demanding sharp tooling and steady feed rates.
Fastening requires careful preparation: nailing and screwing properties are rated good, but pre-boring is strictly necessary to prevent splitting in such dense wood. When it comes to adhesives and resin interface coats, the CIRAD sheet specifically emphasizes that Keranji possesses a very high specific gravity and high extractive content. As a result, it is critical that surface preparation and gluing follow strict shop codes of practice and the specific instructions provided on the adhesive manufacturer’s technical data sheet.
Natural Durability and Regulatory Status
Keranji heartwood is rated as Durability Class 3 (moderately durable against wood-decay fungi) and Class M (moderately durable against termites). However, it is rated Class S (susceptible) to dry-wood borers throughout all of the wood, and heartwood treatability is Class 3 (poorly permeable). Its natural durability corresponds to Class 2 interior use (under cover, dampness possible). For trade compliance, Dialium species listed under Keranji are not restricted under CITES Appendices (Washington Convention 2025).
Frequently Asked Questions
What are the primary visual characteristics of Keranji?
Keranji features yellow-brown heartwood that turns browner with exposure, displaying lustrous stripes and fine silver figure that produces very fine horizontal stripes. Vessels often contain yellow or brown deposits, contrasting with the clearly demarcated, white-to-yellowish sapwood.
How hard is Keranji compared to standard tabletop hardwoods?
Keranji registers a 12.3 on the French Monnin hardness scale, which is an indentation metric where higher numbers denote harder wood. It offers exceptional resistance to surface crushing and denting, backed by a crushing strength of 103 MPa.
Can Keranji be machined using standard steel blades?
Standard high-speed steel tools will dull rapidly. CIRAD recommends stellite-tipped saw blades and tungsten carbide cutting edges to manage Keranji’s high density and interlocking grain patterns without overheating the tools.
Why does Keranji require special attention during gluing and resin bonding?
Due to its very high specific gravity (1.05) and natural extractive content, wood pores are dense and extractive deposits can hinder adhesive penetration. Thorough mechanical surface preparation and adherence to the adhesive manufacturer’s technical instructions are mandatory for long-term bond integrity.
What risks are involved when drying Keranji slabs for furniture builds?
Keranji dries at a normal to slow pace and carries high risks of both surface checking and distortion (warping). Care must be taken to dry slabs gradually using mild temperatures (recommended 45 to 65 °C) to minimize cracks along the slab face.
Does Keranji require international trade permits under CITES?
No. Keranji (covering Dialium cochinchinensis, Dialium indum, Dialium platysepalum, and Dialium p.p.) is not listed in the CITES Appendices according to the 2025 Washington Convention guidelines.
Sources
Published October 31, 2026. Sources are linked in the text.
Header image: original graphic by BigEpoxy.com.
Staff note: Because Keranji heartwood is rated Class S (susceptible) to dry-wood borers across all the wood, any slabs showing pinholes or pest evidence should receive an appropriate preservative treatment before being enclosed in an epoxy assembly. (Source: CIRAD Tropix 7 technical sheet: Keranji.)