Working with Red Grandis in Epoxy River Tables
Red grandis (Eucalyptus grandis), also traded simply as grandis, is a hardwood native to Australia that is now cultivated across tropical and subtropical regions, with European imports primarily originating from Latin America, particularly Brazil and Uruguay. According to the timber research data published in the CIRAD Tropix technical sheet, this species produces lumber ranging in appearance from pale pink to reddish brown, with a clearly demarcated sapwood band measuring 2 to 4 cm thick. The wood exhibits a coarse texture and grain that runs straight to slightly interlocked. When sourced from logs spanning 30 to 60 cm in diameter, Red grandis yields clean, warm-toned boards suitable for modern river table designs.
Density, Weight, and Hardness Ratings
At 12% moisture content, Red grandis presents an average specific gravity of 0.60, typically varying between 0.55 and 0.65 depending on plantation origin and tree maturity. In practical tabletop terms, this translates to an average density of about 37.5 lb/ft³, meaning a standard 2-inch-thick tabletop slab weighs approximately 6.2 lb per sq ft. This moderate weight makes it manageable in the shop without sacrificing physical presence or rigidity.
Mechanical testing from CIRAD Tropix records a Monnin hardness of 2.5 at 12% moisture content. The Monnin scale is an established French hardness measurement where higher values indicate harder material; it is fundamentally distinct from the American Janka test and should never be translated into Janka figures. A rating of 2.5 places mature Red grandis in a medium hardness category that resists daily tabletop denting, backed by a static bending strength of 103 MPa (about 14,940 psi), a crushing strength of 59 MPa (about 8,560 psi), and a modulus of elasticity of 15,200 MPa (about 2,205,000 psi).
Shrinkage, Stability, and the Epoxy River Interface
The primary technical challenge when marrying Red grandis slabs to cured polymer resin lies in its dimensional movement. From green to oven-dry condition, Red grandis exhibits a total tangential shrinkage of 10.0% and a total radial shrinkage of 5.8%. Its ratio of tangential to radial shrinkage (St/Sr) is 1.7, with a coefficient of volumetric shrinkage of 0.48% per 1% change in moisture content. The fiber saturation point is documented at 31%.
Because cured epoxy resin does not shrink or expand alongside ambient humidity swings, bonding wood with a 10.0% tangential shrinkage potential demands strict equilibrium moisture control. Slabs must be thoroughly acclimated to indoor service levels before the river pour occurs. If high-shrinkage boards fluctuate significantly in service, the differential movement exerts severe shear stress along the epoxy-to-wood bond line. Applying a deep penetrating epoxy seal coat across all live edges and wood surfaces helps mitigate atmospheric moisture transfer.
Drying Challenges and Growth Stresses
Drying Red grandis requires deliberate patience. CIRAD Tropix classifies its drying rate as normal to slow, accompanied by a high risk of distortion and a high risk of surface and internal checking. Kiln operators also encounter risks of casehardening and cell collapse. Suggested kiln schedules operate within mild temperature boundaries between 45 °C and 65 °C (about 113 °F to 149 °F). Like many eucalypts, the timber develops internal growth stresses during initial conversion, which can introduce severe splitting or distortion during log sawing unless symmetrical or turning saw methods are used.
Machining, Tooling, and Assembly
Despite having only slightly interlocked grain, Red grandis carries a high blunting effect on cutting tools. CIRAD recommends stellite-tipped saw teeth and tungsten carbide tooling to maintain clean edges and prevent tear-out during milling, jointing, and planing. For furniture assembly, screw-holding is rated as good, though pre-boring pilot holes is strictly necessary to avoid split edges near joints and mounting hardware.
Natural Durability, Treatability, and CITES Status
The heartwood offers durability class 2 to 4 against xylophagous fungi, marking it as durable to poorly durable. It is durable against dry-wood borers (Class D, risk limited to the demarcated sapwood) but susceptible to termites (Class S). Heartwood permeability is classified as poorly or not permeable (Class 3-4). Under the Washington Convention 2025, Red grandis is not listed in the CITES Appendices. CIRAD Tropix catalogs its primary commercial end-uses as current furniture or furniture components, interior and exterior joinery, flooring, panelling, glued laminated elements, and light carpentry.
| Property | CIRAD Tropix value | What it means / US units |
|---|---|---|
| Botanical name(s) | Eucalyptus grandis | |
| Other trade names | Eucalyptus grandis, Grandis | |
| Colour / texture / grain | Red brown; texture coarse; grain straight or interlocked; interlocked grain slight | |
| Specific gravity (12% MC) | 0.60 | about 37.5 lb/ft³; a 2-inch-thick slab weighs about 6.2 lb per sq ft |
| Monnin hardness (12% MC) | 2.5 | French hardness scale; higher = harder (not a Janka value) |
| Total tangential shrinkage | 10.0 % | green to oven-dry |
| Total radial shrinkage | 5.8 % | green to oven-dry |
| Ratio St/Sr | 1.7 | closer to 1 = less cupping tendency |
| Coefficient of volumetric shrinkage | 0.48 % per % MC | volume change per 1% change in moisture content |
| Fibre saturation point | 31 % | |
| Thermal conductivity | 0.22 W/(m·K) | |
| Crushing strength (12% MC) | 59 MPa | about 8,560 psi |
| Static bending strength (12% MC) | 103 MPa | about 14,940 psi |
| Modulus of elasticity (12% MC) | 15,200 MPa | about 2,205,000 psi |
| Decay (fungi) resistance | Durability class 2 to 4 – durable to poorly durable | |
| Termite resistance | Class S – susceptible | |
| Dry-wood borer resistance | Class D – durable (sapwood demarcated, risk limited | |
| Heartwood treatability | Class 3-4 – poorly or not permeable | |
| Use class from natural durability | Class 2 (inside or under cover, dampness possible) to class 3 (not in ground contact, outside) | |
| Drying | rate normal to slow; distortion: high risk; checking: high risk; collapse: yes; casehardening: yes | |
| Suggested kiln program temperatures | 45–65 °C | about 113–149 °F |
| Machining | blunting high; 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). Notes. Native to Australia, this timber species has been planted in almost all tropical or sub-tropical regions. Today, woods imported in Europe mainly come from Latin America (Brazil, Uruguay). |
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).
Is It a Good Epoxy Table Wood?
Red grandis is a viable, attractive option for indoor epoxy river tables, but it requires careful lumber selection and strict moisture discipline. Its attractive reddish-brown color, moderate weight of 37.5 lb/ft³, and reliable bending strength work well for dining tops. However, because of its 10.0% tangential shrinkage, 1.7 shrinkage ratio, and high blunting effect on tools, builders must ensure stock is fully stabilized, stress-free, and thoroughly sealed before pouring epoxy.
Sources
Published October 30, 2026. Sources are linked in the text.
Header image: original graphic by BigEpoxy.com.
Staff note: Log conversion for Red grandis frequently unleashes severe internal growth stresses, making quartersawn or carefully balanced flitches the safest choice to avoid post-machining twist before your resin pour. (Source: CIRAD Tropix 7 technical sheet: Red grandis.)