Resak Wood River Tables: Stability, Resin & Slab Guide

Resak Slabs and Characteristics for Epoxy Tabletops

Resak is a commercial timber group from Asia-Oceania encompassing several species across two genera: Cotylelobium (including C. burkii, C. lanceolatum, C. melanoxylon, and Cotylelobium p.p.) and Vatica (including V. maingayi, V. mangachapoi, V. rassak, and Vatica p.p.). According to the CIRAD Tropix technical sheet, the wood is not listed in the CITES Appendices (Washington Convention 2025). Because it groups two separate genera, physical and technological properties can vary somewhat between individual species and origins.

For tabletop builders sourcing wide slabs, mature Resak logs typically measure from 80 to 100 cm in diameter, offering ample width for dining surfaces or river table banks. The sapwood band is roughly 5 to 10 cm thick and is not always clearly demarcated from the heartwood, presenting a whitish to yellowish tone. Fresh heartwood begins as a pale yellow before darkening to a deep reddish chocolate brown or brown with a greenish tinge. Resak features a fine texture, straight or slightly interlocked grain, and an apparent silver figure across cleanly planed faces.

Weight, Hardness, and Dimensional Movement

Resak is a heavy, dense hardwood with a specific gravity of 0.80 at 12% moisture content. In the shop, this translates to roughly 49.9 lb/ft³, meaning a 2-inch-thick tabletop slab weighs about 8.3 lb per square foot before casting resin. Resak’s hardness is rated at 5.6 on the Monnin hardness scale—a French testing scale where higher numerical values represent harder timbers, not to be confused with or converted to Janka values.

When designing an epoxy river table, wood movement next to cured resin is a critical factor. Resak shows moderate to low shrinkage values: total tangential shrinkage is 4.7% and total radial shrinkage is 2.6%, producing a T/R ratio of 1.8. A ratio under 2.0 indicates a modest tendency toward cupping. Resak’s coefficient of volumetric shrinkage is 0.45% per 1% change in moisture content, with a fiber saturation point at 22%. Because the wood exhibits stable, balanced shrinkage, the mechanical shear stress placed on the epoxy-wood joint during normal interior seasonal shifts remains manageable, provided the slabs are thoroughly dried before casting.

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).

Drying Behavior, Machining, and Resin Exudation

Drying Resak proceeds at a normal to slow pace. CIRAD Tropix records a slight risk of distortion and a slight risk of checking, while collapse and casehardening present no known specific risks. Recommended kiln drying schedules run between 53 °C and 65 °C (about 127 °F to 149 °F).

Machining Resak requires heavy-duty shop equipment. The wood contains silica deposits and exerts a fairly high blunting effect on standard steel tooling. CIRAD advises stellite-tipped saw blades and tungsten carbide cutting knives for shaping edges and surfacing table faces. Screwing and nailing hold well, but pre-boring is strictly necessary to prevent splitting the dense grain.

Resak’s natural heartwood durability is notable: it ranks as Durability Class 2 (durable) against decay fungi, Class D (durable) against dry-wood borers, and Class D (durable) against termites, corresponding to Use Class 3. The heartwood is impermeable to preservatives (Class 4 treatability). However, Resak exhibits two specific assembly challenges noted in the CIRAD Tropix data sheet: resin exudation and high density. The technical notes indicate difficult finishes due to natural resin, and high specific gravity dictates that gluing must be executed carefully in full compliance with the code of practice.

Documented End-Uses

Beyond modern resin-embedded tabletops, Resak is traditionally selected for heavy structural and high-wear applications, including:

• Flooring and indoor staircases
• Glued laminated beams
• Interior and exterior joinery
• Carpentry and wood frame houses
• Exterior decking
• Ship building and open boats

Practical Pre-Pour Checklist for Resak Slabs

1. Inspect species uniformity: Verify grain direction and heartwood-to-sapwood transitions across your boards, remembering that Resak covers both Cotylelobium and Vatica species with slight variations.
2. Ensure kiln-dried moisture targets: Confirm the timber has completed its slow drying cycle down to interior equilibrium (around 12% moisture content) to avoid movement against the polymer.
3. Tool with carbide: Surface slab faces and live edges with fresh tungsten carbide cutters to handle natural silica deposits and minimize tearout from slight grain interlock.
4. Address resin exudation at the bondline: Inspect edge faces for natural resin exudation; clean and degrease contact surfaces thoroughly so the resin does not interfere with epoxy adhesion.
5. Follow rigorous gluing practice: Because Resak possesses high specific gravity (0.80) and Class 4 heartwood impermeability, apply a thin epoxy seal coat along all river edges and let it cure or tack according to your resin manufacturer’s data sheet before the main river pour.
6. Pre-bore table base fasteners: Drill full-depth pilot holes for threaded inserts or lag screws when securing the cured tabletop to its metal or wood base.
7. Test topcoat compatibility: Due to natural wood resin causing difficult finishes, apply sample topcoats on scrap cutoffs to confirm curing and clarity before coating the final tabletop.

Sources

• CIRAD Tropix 7 technical sheet: Resak
• CIRAD Tropix 7 technical sheets (index)

Published October 31, 2026. Sources are linked in the text.

Header image: original graphic by BigEpoxy.com.