Working with Jarrah in Custom Epoxy Tables
Jarrah (Eucalyptus marginata) is native to the coastal belt of southwestern Australia and represents one of the principal timber species for the Australian sawmill industry. For epoxy table makers, Jarrah offers striking visual character. The heartwood ranges from a uniform pink to dark red, naturally maturing into a deep brownish red with age and air exposure. Older trees typically possess narrow, pale sapwood that contrasts cleanly against the heartwood. Featuring an even, moderately coarse texture and grain that is frequently interlocked or wavy, Jarrah provides distinctive grain patterns for river tables and conference tops.
Shrinkage and Dimensional Movement
Managing wood movement is critical when fusing raw timber slabs with solid epoxy resin. Cured epoxy is dimensionally rigid, meaning any expansion or contraction within the wood creates stress along the bond line. Timber moves unequally depending on grain orientation, with tangential movement consistently outpacing radial movement.
Jarrah undergoes significant dimensional change from green to ovendry conditions, making kiln drying and moisture stabilization essential:
| Physical Property | Measurement | Moisture Condition |
|---|---|---|
| Radial Shrinkage | 7.7% | Green to ovendry |
| Tangential Shrinkage | 11.0% | Green to ovendry |
| Volumetric Shrinkage | 18.7% | Green to ovendry |
| Weight / Density | 865 kg m–3 (54 lb ft–3) | At 12% moisture content |
Because tangential shrinkage measures 11.0% compared to 7.7% radial shrinkage, flatsawn Jarrah slabs move substantially more across their face than quartersawn stock. If wood is cast while retaining excess moisture, subsequent tangential shrinkage causes tension against the cured resin, risking bond failure or warp. Slabs must be thoroughly dried to a stable moisture content matching their final indoor environment prior to epoxy work.
Density, Gum Veins, and Epoxy Preparation
Jarrah is a heavy timber, weighing 865 kg m–3 (54 lb ft–3) at 12% moisture content. Denser and heavier hardwoods naturally provide superior resistance against everyday dents and surface wear, making Jarrah tabletops resilient under heavy dining or office use.
When planning an epoxy pour with Jarrah boards, follow these qualitative preparation steps:
- Apply an initial seal coat: Due to the moderately coarse texture and wavy grain, sealing all edges and surfaces with a brush coat of epoxy prevents entrapped air from bleeding into deep resin pours.
- Stabilize gum veins and pockets: A characteristic defect of Jarrah is the presence of internal gum veins or pockets, which can separate sections of the wood. These voids should be thoroughly cleared of loose debris and filled with epoxy resin to lock the structural integrity of the slab.
- Fasten with movement allowance: Heavy slabs continue to respond to seasonal humidity changes. Always mount completed Jarrah river tables to bases using slotted holes to allow cross-grain movement without cracking the wood or resin seam.
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: Inspect live-edge Jarrah slabs carefully before layout, as gum veins and pockets can run deep into the heartwood; stabilizing these pockets with clear or tinted resin turns a natural structural defect into an eye-catching design element. Reference material available via the USDA Wood Handbook (FPL-GTR-282).