Introduction to Agba (Tola Branca)
Agba (Gossweilerodendron balsamiferum), also traded under names such as Tola branca, is an African hardwood harvested from regions including Angola, Cameroon, Republic of the Congo, the Democratic Republic of the Congo, Gabon, and Nigeria. Derived from large trees with log diameters typically measuring from 70 to 110 cm, Agba yields wide boards and slabs suitable for large furniture projects. According to technical documentation published by CIRAD Tropix, Agba is well-established in commercial joinery and furniture making, but its specific physical and chemical traits require careful handling when preparing it for deep epoxy pours.
Appearance, Figure, and Wood Characteristics
Agba displays a warm, subdued aesthetic. The heartwood ranges from yellow brown to light brown, while the sapwood measures between 5 and 10 cm in thickness and is not clearly demarcated from the interior wood. The texture is medium, with grain that is straight or slightly interlocked.
Woodworkers evaluating raw boards will notice two distinct physical characteristics noted in the CIRAD Tropix data: the wood possesses a light peppery odour and features natural resin exudation. Additionally, logs can show ring shakes or wind shakes, which table builders must carefully inspect and stabilize before layout and mold assembly.
Weight, Hardness, and Mechanical Strength
Agba is a medium-density hardwood. At 12% moisture content, it has an average specific gravity of 0.52, which corresponds to a density of about 32.5 lb/ft³. For table builders calculating dead load, a 2-inch-thick tabletop slab weighs approximately 5.4 lb per square foot. This moderate weight makes it manageable in the workshop compared to dense tropical hardwoods.
On the hardness scale, Agba rates at 2.3 on the Monnin hardness test at 12% moisture content. The Monnin system is a standardized French indentation test where higher numbers reflect harder timber; it operates on a different measurement scale than the Janka test and cannot be directly converted to Janka values. Mechanically, the wood exhibits a crushing strength of 40 MPa (about 5,800 psi), a static bending strength (modulus of rupture) of 74 MPa (about 10,730 psi), and a modulus of elasticity of 10,920 MPa (about 1,584,000 psi).
| Property | CIRAD Tropix value | What it means / US units |
|---|---|---|
| Botanical name(s) | Gossweilerodendron balsamiferum | |
| Other trade names | Tola branca | |
| Colour / texture / grain | Light brown; texture medium; grain straight or interlocked; interlocked grain slight | |
| Specific gravity (12% MC) | 0.52 | about 32.5 lb/ft³; a 2-inch-thick slab weighs about 5.4 lb per sq ft |
| Monnin hardness (12% MC) | 2.3 | French hardness scale; higher = harder (not a Janka value) |
| Total tangential shrinkage | 5.4 % | green to oven-dry |
| Total radial shrinkage | 2.4 % | green to oven-dry |
| Ratio St/Sr | 2.3 | closer to 1 = less cupping tendency |
| Coefficient of volumetric shrinkage | 0.33 % per % MC | volume change per 1% change in moisture content |
| Fibre saturation point | 27 % | |
| Thermal conductivity | 0.18 W/(m·K) | |
| Crushing strength (12% MC) | 40 MPa | about 5,800 psi |
| Static bending strength (12% MC) | 74 MPa | about 10,730 psi |
| Modulus of elasticity (12% MC) | 10,920 MPa | about 1,584,000 psi |
| Decay (fungi) resistance | Durability class 2 to 3 – durable to moderately durable | |
| Termite resistance | Class S – susceptible | |
| 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 rapid to normal; distortion: no risk or very slight risk; checking: no risk or very slight risk; collapse: no known specific risk; 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).
Shrinkage, Drying, and the Epoxy River Interface
Wood movement is one of the most critical factors in river table longevity. When wood shrinks or expands against rigid cured epoxy, internal stress can cause bond failure or checking. Agba shows very favorable dimensional stability:
- Total tangential shrinkage: 5.4%
- Total radial shrinkage: 2.4%
- Tangential to radial ratio (St/Sr): 2.3
- Coefficient of volumetric shrinkage: 0.33% per 1% change in moisture content
- Fibre saturation point: 27%
CIRAD Tropix records that Agba dries at a rapid to normal rate with no risk or very slight risk of distortion, no risk or very slight risk of surface checking, and no known specific risk of casehardening or collapse. When kiln dried, recommended programs employ temperatures between 55 and 65 °C (about 131 to 149 °F). Its low volumetric shrinkage coefficient and minimal distortion risk help keep tabletop glue lines and epoxy seams stable over changing seasons.
Machining, Gluing, and Resin Considerations
Agba performs smoothly under standard cutting equipment. Its blunting effect on cutters is rated as normal, allowing the use of ordinary or alloy steel saw teeth and ordinary cutting tools. Both slicing and peeling properties are rated as good, and nailing and screwing hold well.
However, builders must take specific precautions during preparation:
- Resin Clogging: The natural resin in Agba tends to clog blades, router bits, and abrasives. Tool edges should be cleaned regularly.
- Dust Irritation: The fine sawdust can be an irritant; appropriate shop dust collection and personal protection are recommended.
- Acidity and Gluing: The wood is described as fairly acid, which introduces risks of staining when gluing. Clean, freshly machined surfaces and careful resin-maker adhesive protocols are essential to prevent unexpected discoloration at the joint line.
Natural Durability, Regulatory Status, and End-Uses
Agba heartwood is categorized as Durability Class 2 to 3 (durable to moderately durable) against xylophagous fungi, yielding a natural durability use class rating of Class 2 (interior or under cover, where dampness is possible). However, it is rated as Class S (susceptible) to termites and dry-wood borers across all the wood, and the heartwood is poorly permeable (Class 3 treatability).
Regarding trade and sourcing regulations, Agba is not listed in the CITES Appendices (Washington Convention 2025). Its primary traditional end-uses include interior and exterior joinery, current furniture and furniture components, sliced veneer, glued laminated components, moulding, interior panelling, and boat building planking.
Is Agba a Good Wood for Epoxy Tables?
Agba is well-suited for indoor epoxy river tables, desks, and decorative tabletops. Its moderate density (32.5 lb/ft³) keeps large tops easy to handle, its shrinkage values are modest, and its drying behavior shows almost no tendency toward warping or checking next to an epoxy river. Table makers must simply prepare for its natural resin content when machining and take care with its acidity to avoid chemical staining along glued edges.
Sources
Published October 30, 2026. Sources are linked in the text.
Header image: original graphic by BigEpoxy.com.
Staff note: When inspecting Agba stock for a river table build, watch carefully for wind shakes or internal ring shakes in the core of large slabs, as these natural log separations must be completely sealed with epoxy to prevent air leakage into the main river pour. (Source: CIRAD Tropix 7 technical sheet: Agba.)