Macawood (Platymiscium spp.) for Epoxy River Tables
Macawood, also commonly recognized in trade as cristobal, is a tropical timber valued for fine furniture, decorative surfaces, and custom river tables. When integrating timber slabs with solid resin casts, wood stability is essential. Unchecked shrinkage or swelling can break epoxy bond lines, induce internal stresses, or bow tabletop assemblies. Examining documented dimensional properties provides clear expectations for how Macawood behaves through humidity shifts.
Shrinkage and Dimensional Stability Data
Data compiled by the Forest Products Laboratory reveals that Macawood possesses remarkably low overall shrinkage compared to many cabinet-grade timbers. The published shrinkage values from green to ovendry conditions are summarized below.
| Property | Measurement |
|---|---|
| Radial Shrinkage (Green to Ovendry) | 2.7% |
| Tangential Shrinkage (Green to Ovendry) | 3.5% |
| Volumetric Shrinkage (Green to Ovendry) | 6.5% |
Understanding Tangential vs. Radial Movement
Wood shrinks and swells along different grain orientations at differing magnitudes. Tangential movement occurs along the growth rings, whereas radial movement occurs perpendicular across them. In Macawood, tangential shrinkage is 3.5% while radial shrinkage is 2.7%.
The relationship between tangential and radial shrinkage is qualitative proof of how prone a wood slab is to warping, cupping, or casehardening. Because the tangential-to-radial ratio in Macawood is unusually low and close to parity, the timber exhibits exceptional dimensional stability. While flatsawn slabs naturally display slightly greater dimensional change across their width than quartersawn boards, Macawood retains shape consistency far better than higher-shrinkage hardwoods. This uniform movement lowers the likelihood of severe cupping across a wide tabletop slab.
Working with Macawood in Epoxy Table Construction
Building high-end epoxy river tables requires balancing resin behavior against natural wood movement. The properties of Macawood make it an attractive candidate when paired with good shop practices:
- Drying to Equilibrium: Slabs must be thoroughly dried to a stable moisture content before casting. Casting wet wood locks excess moisture inside the assembly, resulting in bond failure and internal tension as the core attempts to balance with room humidity.
- Sealing the Live Edge: Applying a thin seal coat of epoxy across the live edge and mating surfaces prevents trapped air from venting into deep resin pours, while promoting a strong mechanical interface between timber and resin.
- Accommodating Seasonal Expansion: While Macawood displays minimal dimensional shifts, cured resin does not swell or contract with moisture changes. Slotted screw holes on table understructures and flexible tabletop clips allow the wood components to breathe naturally without pulling apart the central epoxy seam.
- Surface Longevity: Dense, firm hardwood fibers resist everyday surface dents and localized compression, matching the durability of cured epoxy under daily dining or conference room use.
Sources
USDA Wood Handbook (FPL-GTR-282)
Published October 28, 2026. Sources are linked in the text.
Header image: original graphic by BigEpoxy.com.
Staff note: Also known in regional trade as cristobal, Macawood exhibits a modest volumetric shrinkage of 6.5% in the USDA Wood Handbook (FPL-GTR-282), ensuring exceptionally low stress along the epoxy interface once properly seasoned.