How to make an epoxy river table: a step-by-step guide

What you’ll need

• Two live-edge slabs (or one slab ripped down the middle), dried and roughly the same thickness.
• Deep-pour epoxy — enough for the river plus a margin. A tabletop epoxy for the final coat, if you’re finishing with epoxy.
• Melamine board or HDPE sheet for the form, plus screws, silicone sealant and/or mold release tape.
• Mixing buckets, a drill paddle for large batches, gloves and eye protection.
• A router with a sled and flattening bit (or access to a wide-belt sander), a random orbital sander and sandpaper from about 80 grit up.
• Clamps, a level, a heat gun or torch, and a flat, level surface that can stay undisturbed for several days.

1. Choose and prepare the wood

Use wood that is properly dry — furniture makers commonly aim for a moisture content in the single digits for indoor pieces, and a moisture meter is cheap insurance. Wet wood keeps moving as it dries and can crack the epoxy or pull away from it. Remove loose bark (or stabilize it with thin epoxy if you want to keep it), clean out soft or punky spots with a wire brush, and flatten both slabs so they sit flat in the form. The river edges are the feature: clean them up, but leave their shape.

2. Measure and calculate the epoxy

With the slabs positioned, measure the river width every 12 in or so along its length and average the readings. For depth, use the slab thickness plus the little extra you’ll pour proud of the wood — most people fill 1/16 in (1–2 mm) over, because the whole top gets flattened afterward. Multiply length × average width × depth for the volume, then add about 10%. Don’t forget any voids, cracks or knot holes you plan to fill at the same time.

3. Build a form that won’t leak

The form is a shallow box slightly larger than the finished table. Melamine-faced board is popular because epoxy releases from it reasonably well once taped; HDPE sheet releases even more easily and can be reused. Line every inside surface with mold release tape or packing tape, screw the sides to the base, and run a bead of silicone along every inside seam. Let the silicone cure before you pour.

Leaks are the classic river-table disaster. Epoxy is thin and finds any gap, and a 4-gallon pour weighs around 35–40 lb pressing on the seams. Don’t test a melamine form with water — the particleboard edges swell and any moisture left behind clouds the epoxy. Instead, run your finger along every sealed seam, and on a big pour consider mixing a small first batch and watching the seams for a few minutes before you commit the rest.

4. Secure and seal the slabs

Clamp or screw the slabs down to the form base (from underneath, or with cleats across the top). Deep-pour epoxy is dense, and wood floats — an unsecured slab will rise and tilt. Then brush a thin seal coat of epoxy over the live edges, bark and any end grain facing the river. This closes the pores so air doesn’t bubble out of the wood into the main pour. Let it cure to the point the label says you can pour over it.

5. Mix and pour

Work in the temperature range on the product label — many deep-pour epoxies are formulated for room temperature somewhere around 70–80°F (21–27°C); MAS Epoxies, for example, asks for 60–80°F for its Deep Pour X and warns against using it above 85°F. A cold shop can stretch a multi-day cure much further, and a hot one makes the pour behave like a deeper one; the cure time calculator adjusts the label times for your temperature. Measure the two parts exactly, mix slowly for the full time the label specifies, scraping the sides and bottom, and pour steadily into the river. If you’re coloring the resin, mix the pigment in thoroughly before pouring.

• Mix in batches you can handle — often 1–2 gallons at a time for a drill paddle, less by hand.
• Pour batches back to back so they merge while wet.
• Pass a heat gun or torch lightly over the surface to pop bubbles — and come back to it. Deep-pour resin is slow, and bubbles keep rising from the wood for hours.
• Cover the form to keep dust off, without letting the cover touch the resin.

6. Pour in lifts if needed

Every deep-pour product has a maximum depth per pour — and many have a minimum, too (MAS Deep Pour X lists 2 in), so check that your slab thickness sits inside the label’s range before you buy. If your slabs are thicker than the maximum, pour in lifts: fill to the maximum, let it cure to the recoat window on the label, then pour the next layer. Pouring deeper than the label allows traps heat, and overheated epoxy can crack, yellow, or cure with a cloudy, bubbly look. Deep pours also cure slowly — often several days before you can demold — so don’t rush it.

7. Demold and flatten

Once the epoxy has cured enough to machine (check the label — full cure often takes longer), unscrew the form and pop the table out. The top will not be perfectly flat: epoxy shrinks slightly, and the slabs may sit proud of the river. Flatten the whole top with a router sled and a flattening bit, taking shallow passes, then flip it and do the underside.

8. Sand

Sand the whole table through the grits — commonly starting around 80 grit after flattening and working up through 120, 180, 220 and beyond. Don’t skip grits; scratches from a coarse paper will show through a clear finish. Epoxy dust is fine and irritating, so use dust extraction and a suitable mask.

9. Finish

There are two common routes:

• Epoxy flood coat: pour a thin tabletop epoxy over the entire top for a glossy, glass-like finish. This needs its own calculation — see the tabletop calculator.
• Oil, hardwax oil or polish: sand the epoxy to a high grit and polish it to a shine, then finish the wood with an oil or hardwax oil. The result looks more like furniture and less like a coating.

Common river table problems

Take your time with steps 1–4. Almost everything that goes wrong in a river table is decided before the first drop of epoxy is poured.