Kosipo in Custom Epoxy River Builds
Kosipo (Entandrophragma candollei), also traded under names like Kosipo-mahogany and Omu, is a heavy African hardwood from the Meliaceae family. Originating from countries such as Cameroon, Gabon, Côte d’Ivoire, and the Democratic Republic of the Congo, it is frequently chosen for high-class furniture, cabinetwork, and joinery. When combined with deep-pour epoxy in river tables or conference tops, its mechanical strength and rich color provide an impressive focal point. However, working with Kosipo requires careful attention to its natural extractives, blunting effect on tools, and drying tendencies as detailed in technical testing by CIRAD Tropix.
Appearance, Texture, and Grain Structure
Kosipo heartwood features a red brown tone, often exhibiting purplish glints, and naturally darkens when exposed to ambient light. The sapwood is clearly demarcated, typically ranging from 4 to 8 cm in thickness. On quartersawn faces, the wood displays a distinct ribbon-like aspect. The overall grain is straight to slightly interlocked, accompanied by a coarse texture. A critical detail for woodworkers is the presence of black resin deposits inside the pores, which requires targeted preparation when bonding casting resins or applying topcoats.
Density, Monnin Hardness, and Mechanical Strength
Kosipo is a moderately heavy hardwood. At 12% moisture content, it has an average specific gravity of 0.69, yielding a density of about 43.1 lb/ft³. In the shop, this translates to roughly 7.2 lb per square foot for a standard 2-inch-thick slab, requiring stout leg bases and level staging during pours.
Its surface resistance is recorded at 3.3 on the Monnin hardness scale. The Monnin scale is a French standardized test where a higher number denotes a harder wood surface; it operates under a different testing protocol than the North American Janka test and should never be translated into Janka figures. In terms of overall structural integrity, mature Kosipo exhibits a crushing strength of 53 MPa (about 7,690 psi), a static bending strength (modulus of rupture) of 87 MPa (about 12,620 psi), and a modulus of elasticity of 11,190 MPa (about 1,623,000 psi).
Shrinkage, Stability, and Epoxy Interface Behavior
When anchoring timber slabs directly to cured polymer resin, predictable shrinkage numbers are vital. Kosipo has a fiber saturation point of 32%. Total tangential shrinkage from green to oven-dry is 6.7%, while total radial shrinkage is 4.8%. This produces a tangential-to-radial shrinkage ratio (St/Sr) of 1.4, which indicates a low cupping tendency compared to species with wider dimensional disparities. Its unit volumetric shrinkage is 0.42% for every 1% change in moisture content.
In practical river table construction, quartersawn stock remains the most stable option. The CIRAD Tropix data sheet notes that backsawn boards present a greater challenge, drying more slowly and carrying a high risk of distortion, whereas risk of checking, collapse, and casehardening is low or absent.
Tooling, Machining, and Surface Preparation
Working Kosipo demands significant machine power. The CIRAD Tropix research highlights a high blunting effect on cutting edges, varying from quite high to very high due to the natural presence of silica in the wood. Woodworkers should run stellite-tipped saw teeth and tungsten carbide cutting knives. Slight interlocked grain may also lead to localized grain tearing during planing or routing operations.
Because the pores contain natural black resin deposits, the adherence of finishing coats can be compromised. Sanding must be completed with care, and pore filling is explicitly noted as necessary to achieve a clean, smooth finish before applying final topcoats.
Durability and International Trade Status
Kosipo heartwood is rated as durability class 2 to 3 against xylophagous fungi (durable to moderately durable), class M (moderately durable) against termites, and class D (durable) against dry-wood borers, with borer risks largely restricted to the sapwood. Its heartwood treatability is class 3 (poorly permeable). It meets the conditions for use class 3 (exterior applications out of ground contact). Regarding trade controls, Entandrophragma candollei is not listed in the CITES Appendices under the Washington Convention 2025 regulations.
| Property | CIRAD Tropix value | What it means / US units |
|---|---|---|
| Botanical name(s) | Entandrophragma candollei | |
| Other trade names | Kosipo-mahogany, Omu | |
| Colour / texture / grain | Red brown; texture coarse; grain straight or interlocked; interlocked grain slight | |
| Specific gravity (12% MC) | 0.69 | about 43.1 lb/ft³; a 2-inch-thick slab weighs about 7.2 lb per sq ft |
| Monnin hardness (12% MC) | 3.3 | French hardness scale; higher = harder (not a Janka value) |
| Total tangential shrinkage | 6.7 % | green to oven-dry |
| Total radial shrinkage | 4.8 % | green to oven-dry |
| Ratio St/Sr | 1.4 | closer to 1 = less cupping tendency |
| Coefficient of volumetric shrinkage | 0.42 % per % MC | volume change per 1% change in moisture content |
| Fibre saturation point | 32 % | |
| Thermal conductivity | 0.23 W/(m·K) | |
| Crushing strength (12% MC) | 53 MPa | about 7,690 psi |
| Static bending strength (12% MC) | 87 MPa | about 12,620 psi |
| Modulus of elasticity (12% MC) | 11,190 MPa | about 1,623,000 psi |
| Decay (fungi) resistance | Durability class 2 to 3 – durable to moderately durable | |
| Termite resistance | Class M – moderately durable | |
| Dry-wood borer resistance | Class D – durable (sapwood demarcated, risk limited | |
| Heartwood treatability | Class 3 – poorly permeable | |
| Use class from natural durability | Class 3 – not in ground contact, outside | |
| Drying | rate normal to slow; distortion: high risk; checking: no risk or very slight risk; collapse: no known specific risk; casehardening: no known specific risk | |
| Suggested kiln program temperatures | 53–62 °C | about 127–144 °F |
| Machining | blunting high; saw teeth: stellite-tipped; cutting tools: tungsten carbide | |
| 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).
Practical Pre-Pour Checklist for Kosipo
- Inspect the cut orientation: Verify whether your slab is quartersawn or backsawn, keeping in mind that backsawn Kosipo has a significantly higher risk of distortion.
- Confirm uniform moisture content: Ensure the wood is thoroughly dried—following suggested kiln cycles between 53 °C and 62 °C (about 127 °F to 144 °F)—to minimize differential movement against the cured epoxy mass.
- Equip carbide tooling: Outfit your slab-flattening routers and table saws with tungsten carbide or stellite-tipped blades to handle the silica-induced blunting.
- Examine live edges for sapwood borers: If preserving the demarcated 4 to 8 cm sapwood edge, inspect it thoroughly, as borer resistance applies specifically to the heartwood.
- Cleanse pore resin deposits: Inspect the coarse pores for black resin deposits and prep the contact edge according to your epoxy manufacturer’s data sheet.
- Plan a grain-filling schedule: Account for Kosipo’s coarse texture by incorporating pore-filling steps into your finishing process to achieve an even final surface.
Sources
Published October 30, 2026. Sources are linked in the text.
Header image: original graphic by BigEpoxy.com.
Staff note: If you are building a live-edge river table that keeps the natural perimeter, remember that the demarcated sapwood (4 to 8 cm thick) lacks the heartwood’s natural resistance to dry-wood borers, meaning any insect activity or damage in the raw slab is almost exclusively concentrated in that pale outer layer. (Source: CIRAD Tropix 7 technical sheet: Kosipo.)