Working with Suren in Epoxy River Tables
Suren encompasses timber from several species in the Toona genus—principally Toona calantas, Toona ciliata, and Toona sureni—originating from Asia-Oceania. Known for its warm appearance and aromatic qualities, Suren is traditionally utilized for current furniture, interior joinery, mouldings, musical instruments, cigar boxes, and boat building. For custom tabletop and epoxy river builders, technical test data published in the CIRAD Tropix technical sheet provides clear guidance on how this timber behaves when combined with epoxy resin.
| Property | CIRAD Tropix value | What it means / US units |
|---|---|---|
| Botanical name(s) | Toona calantas, Toona ciliata, Toona sureni | |
| Colour / texture / grain | Red brown; texture medium; grain straight; interlocked grain absent | |
| Specific gravity (12% MC) | 0.50 | about 31.2 lb/ft³; a 2-inch-thick slab weighs about 5.2 lb per sq ft |
| Monnin hardness (12% MC) | 3.5 | French hardness scale; higher = harder (not a Janka value) |
| Total tangential shrinkage | 6.3 % | green to oven-dry |
| Total radial shrinkage | 3.8 % | green to oven-dry |
| Ratio St/Sr | 1.7 | closer to 1 = less cupping tendency |
| Coefficient of volumetric shrinkage | 0.56 % per % MC | volume change per 1% change in moisture content |
| Fibre saturation point | 23 % | |
| Thermal conductivity | 0.18 W/(m·K) | |
| Crushing strength (12% MC) | 45 MPa | about 6,530 psi |
| Static bending strength (12% MC) | 75 MPa | about 10,880 psi |
| Modulus of elasticity (12% MC) | 8,400 MPa | about 1,218,000 psi |
| Decay (fungi) resistance | Durability class 3 to 4 – moderately to 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 slow; distortion: high risk; checking: slight risk; collapse: yes; casehardening: no known specific risk | |
| Suggested kiln program temperatures | 55–65 °C | about 131–149 °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 for River Table Builds
Pros
- Manageable Density: At 12% moisture content, Suren has a specific gravity of 0.50, weighing approximately 31.2 lb/ft³ (roughly 5.2 lb per square foot for a 2-inch slab), making large conference and dining tables easy to move and support.
- Predictable Grain Structure: The wood features straight grain with interlocked grain absent, simplifying jointing and flattening.
- Favorable Shrinkage Ratio: With a tangential-to-radial shrinkage ratio of 1.7, Suren exhibits moderate dimensional behavior across seasonal shifts.
- Tool-Friendly Machining: Suren imposes only normal tool blunting, allowing the use of ordinary cutting tools and ordinary or alloy steel saw teeth.
- Trade Compliance: Suren is not listed in the CITES Appendices (Washington Convention 2025), presenting straightforward sourcing compared to restricted tropical hardwoods.
Cons
- High Distortion and Collapse Risk: The wood carries a high risk of distortion and is prone to collapse during drying, requiring slow, cautious moisture reduction before casting.
- Moderate Hardness: With a Monnin hardness of 3.5, Suren is moderately soft compared to denser furniture woods, making surfaces more prone to denting without a protective topcoat.
- Poor Natural Durability: Heartwood falls into durability class 3 to 4 (moderately to poorly durable) and is susceptible (Class S) to both termites and dry-wood borers.
- Resin Exudation: Natural resin exudation can interfere with resin adhesion if edges and contact surfaces are not properly prepped and sealed.
- Grain Filling Required: The medium-textured surface requires filling before polishing to achieve a uniform, glass-smooth finish.
Physical Properties and River Table Mechanics
When engineering an epoxy river table, wood movement against a rigid cured resin channel determines long-term structural integrity. Suren displays a total tangential shrinkage of 6.3% and a total radial shrinkage of 3.8% from green to oven-dry, resulting in a shrinkage ratio of 1.7. Its coefficient of volumetric shrinkage is 0.56% per 1% change in moisture content, with a fibre saturation point of 23%. Because the ratio sits well below 2.0, quartersawn and riftsawn boards demonstrate minimal tendency to cup, reducing peel stress at the wood-epoxy bond line.
Hardness is evaluated on the French Monnin scale, where Suren scores 3.5. On the Monnin scale, higher values indicate greater hardness (this scale should not be confused with or converted to Janka values). Combined with a crushing strength of 45 MPa (about 6,530 psi), a static bending strength of 75 MPa (about 10,880 psi), and a modulus of elasticity of 8,400 MPa (about 1,218,000 psi), Suren delivers sufficient stiffness and strength for residential tops, though it requires care to prevent localized impact damage.
Build Notes for Epoxy Woodworkers
Slab Selection
Suren logs generally yield diameters from 50 to 70 cm. The sapwood is clearly demarcated, measuring 2 to 3 cm in thickness, with colors ranging from pink to greyish or yellowish-white. The heartwood is red-brown, occasionally accented by dark brown stripes and distinct growth rings. Builders utilizing live edges should carefully inspect the pale sapwood: because the CIRAD Tropix sheet rates sapwood and heartwood as susceptible to dry-wood borers and termites, any evidence of insect tunneling must be removed or stabilized.
Drying Considerations
Drying Suren requires patience. The species has a slow drying rate, a slight risk of checking, but a high risk of distortion alongside a susceptibility to collapse. Kiln programs detailed in CIRAD research recommend starting prewarming phases around 50 to 52 °C and drying through temperatures between 55 and 65 °C (131 to 149 °F). Do not pour epoxy until the core moisture content has stabilized to indoor equilibrium levels to prevent stress-induced debonding.
Machining
Milling Suren is straightforward. Ordinary cutting tools and standard steel sawteeth handle the timber cleanly without excessive blunting. Nailing and screwing performance is rated as good, ensuring that mechanical fasteners, C-channels, and table base mounting plates bite securely into the underside.
Sealing and Finishing
CIRAD Tropix specifically notes that Suren exhibits resin exudation and needs filling before polishing. Builders should degrease live edges and contact faces prior to pouring epoxy to prevent native resins from interfering with epoxy adhesion. Apply a thin epoxy seal coat along the river edges to lock in wood extractives and seal open pores. For top finishing, Suren belongs to natural durability Class 2 (interior or under cover with dampness possible); heartwood treatability is poorly permeable (Class 3-4). Applying a high-grade film or pore-filling tabletop finish will even out the medium texture and protect the wood from surface wear.
Sources
Published October 30, 2026. Sources are linked in the text.
Header image: original graphic by BigEpoxy.com.
Staff note: CIRAD Tropix data highlights that natural Suren heartwood is poorly permeable (treatability Class 3-4), meaning chemical preservative treatments will not deeply penetrate the core; keep finished tables strictly indoors in Class 2 environments. (Source: CIRAD Tropix 7 technical sheet: Suren.)