How to Build a Bench With an Epoxy River

Cut live edge slab

To build a 48-inch bench top, you’ll want a couple of extra inches of material for squaring it later, so cut the two-inch thick wood slab to 50 inches using a circular saw, miter saw, table saw, track saw, or a combination of these depending on the width of your slab and the tools you have available.

TMB STUDIO

Remove the soft wood and bark

After trimming the slab to its rough length, utilize a chisel and a mallet to eliminate the softwood and bark surrounding the edges and internal hollows. A wire brush is a good alternative tool that will allow you to get into small crevices. This ensures the epoxy adheres firmly to the slab’s hardwood.

TMB STUDIO

Rough up the edges

After removing the bark, clamp the slab down to the bench. Use an angle grinder with a wire wheel attachment to rough up the edges and remove any remaining bark. The rough edges the wire wheel creates will help the epoxy resin adhere better, which is essential for a strong bond.

TMB STUDIO

Rip the live edge slab

Rip the slab down the middle using a track saw. Place a piece of sacrificial rigid foam insulation under the slab to prevent damage to the table.

TMB STUDIO

Determine the bench width

To determine the width of the bench, you will need to measure the two pieces of your slab, including the gap for the “river.” Place the two slab pieces so that you can visualize the size of the epoxy “river”. By adjusting the gap between the two pieces, you can shrink or grow the size of the epoxy “river” as desired. The greater the gap between the two slab pieces, the more epoxy resin the bench will require. Once this has been determined, note the measurement from ripped edge to ripped edge.

TMB STUDIO

Build the mold

Once you’ve determined your bench top width and length, it is time to construct the epoxy mold. The slab pieces for our project are 50 inches long and 15-3/4 inches wide (including the “river”), as determined in the previous step. To build the mold:

• Cut a piece of 3/4-inch melamine that is 1-1/2 inches larger than the bench top in both directions. This will be the bottom of your mold. Ours was 51-1/2-inches x 17-1/4-inches.
• For the walls of the mold, cut 3/4-inch melamine strips as wide as the wood slab thickness plus two inches. Using your miter saw, cut these to length so that they rest flush against the outside edge of your mold’s bottom piece.
• Apply a bead of silicone caulk to the underside of the four side walls and clamp them to the bottom of the mold. Ensure that the side walls are properly positioned flush with the outside edge of the bottom and that there is no gap between the pieces of melamine.
• Attach the melamine walls to the mold bottom using brad nails or screws.
• Every seam inside and outside the mold should be sealed with a bead of caulk to ensure the mold is as watertight as possible.
• Allow the mold to dry overnight before using it.

TMB STUDIO

Apply fast-drying epoxy resin to live edges and holes

During the drying process of the mold, it is a good idea to seal any holes in the wood and the edges of the wood that will be adhering to the epoxy. By sealing the edges, you can prevent air bubbles from forming during your epoxy-deep pour. Wearing nitrile gloves, prepare a small batch of fast-drying epoxy resin according to the manufacturer’s instructions. If you plan to dye the epoxy, include the dye in this batch as well.

Apply two coats of epoxy to the wood’s edges and any hairline cracks or knots with a chip brush. Use a 10cc syringe to fill in small, deep holes in the wood. You can use CA glue and super glue accelerator to fill very small holes. Smooth the surface with a scraper after the epoxy has dried.

TMB STUDIO

Scuff up the wood edges

Once the epoxied edges and holes have thoroughly dried, take 320 grit sandpaper and gently sand them. Remove the sanding dust using a shop vac or air compressor. Use a microfiber cloth and isopropyl alcohol 90% to clean the sanded surface.

TMB STUDIO

Prepare the mold

Before setting up your mold:

1. Lay down a tarp or plastic sheeting on the floor to protect it from any drips or spills.
2. Place the mold on a stable surface such as a worktable or sturdy sawhorses and make sure that it is level and will not be disturbed.
3. Use a level to confirm the mold is level and apply shims as necessary. If the mold is not level, the epoxy will not cure evenly.

Remove any dust or dirt that may be present in the mold using a shop vac and cheesecloth. Then, put on a mask and spray the inside of the mold with a silicone lubricant spray. The spray will act as a releasing agent once the epoxy resin has cured. After spraying the mold, use a clean microfiber cloth to rub the lubricant into the surface of the mold.

TMB STUDIO

Fit the wood into the mold

Place the wood pieces in the mold. If something does not fit properly, you can make adjustment cuts to the slab boards at this point. If there is loose wood or dust in the mold, remove it with a cheesecloth to avoid getting trapped in the epoxy resin. Clamp down both pieces of wood tight to the bottom of the mold to prevent epoxy from seeping underneath them.

Note: As a means of clamping the wood securely, I used scrap 2×4 pieces that were taller than the walls of the mold. However, in hindsight, it would have been beneficial to cover the scraps with packing tape or plastic wrap. The epoxy resin stuck to the scraps and took a long time to remove.

TMB STUDIO

Mix the Epoxy

To avoid wasting epoxy resin, you may wish to use epoxy resin calculators available online or calculate the required amount using the formula :

Length of the “river” in inches X Average width of the “river” in inches X Height in inches of the “river” channel. Using the resulting number, divide it by 1.805 to know the amount of fluid ounces you need to use.

In my case, I required 240 oz of epoxy resin for the bench I was making. To be on the safe side, I rounded up the amount to 256 oz (2 gal).

Work in a well-ventilated area and wear a respirator mask and nitrile gloves for safety. There are various mixing ratios for different epoxy resins, so be sure to pay attention to the mixing requirements of your particular epoxy. My project required a 2:1 mixing ratio.

Pour the epoxy base resin and curing agent slowly into a clean and dry plastic measuring bucket. Mix the epoxy using the drill mixing attachment on a low setting, paying particular attention to the edges and bottom of the bucket. Stir for three minutes while scraping the edges with a stir stick.

Epoxy can be colored with dye if you wish. Start with a small amount of dye, since a little goes a long way, especially if it is a concentrated liquid dye. Add a few drops of the dye to the epoxy and stir for two to three minutes. If you don’t want to color your epoxy, continue stirring it for another two minutes.

TMB STUDIO

Pour epoxy into mold

Slowly pour the epoxy into the “river” channel. Don’t over-pour the epoxy and let it spill over the channel. Pouring should be slowed down as the epoxy rises. Pour the epoxy until it reaches the crest and slightly overflows the channel. If you find any additional tiny holes or cracks in the wood, use a chip brush to fill them in with epoxy at this time. Avoid scraping the bucket edges and let gravity do its job while pouring. Unmixed epoxy might be present on the bucket’s edges, so avoiding mixing it with your pour is important.

Eliminate any air bubbles that may rise to the surface after the epoxy has been poured. The best way to accomplish this is with a handheld torch or heat gun. Ensure you maintain a safe distance of approximately five inches from the surface and move the torch quickly in a sweeping motion over it. Avoid holding the heat source on one spot for too long, as this may result in damage to your project. Dust or small wood specks may accidentally fall into the epoxy, but they will typically float to the surface and can be easily removed with a small stirring stick. Over the next two hours, monitor the epoxy and remove any bubbles that may appear.

TMB STUDIO

Protect the epoxy while curing

In a temperature-controlled environment, the epoxy took 72 hours to cure. Unfortunately, I didn’t have an entirely dust-free environment, so I draped a plastic sheet over the mold. If you choose to use this method, please ensure the plastic sheet does not touch the epoxy and the plastic is not taped or secured in such a way as to prevent airflow to it.

TMB STUDIO

Release the bench from the mold

Once the epoxy resin has cured for 72 hours, you can safely remove the mold. To accomplish this, gently knock off the sides of the mold with a mallet. Use wooden wedges or a chisel to separate the bench top from the mold bottom if it sticks.

TMB STUDIO

Plane and sand the bench top

Most of us do not own a planer or sander large enough to smooth out a bench top of this size. To get around this, I recommend searching for a local woodworking shop that offers large slab sanding and planning services. For an epoxy resin bench, a large drum or wide belt sander is an ideal solution for achieving a smooth and even finish.

I found a local shop called The Urban Craftsman in Milwaukee. Nick Hardrath, the owner, was able to plane and sand the bench down to a 1-1/2-in thickness within fifteen minutes.

TMB STUDIO

Square up the bench

Trim the bench width to 48-in. using a track saw or a table saw. In addition, if your bench top has any residual epoxy or chips in the front or back wood edges, trim those down with the saw as well.

TMB STUDIO

Route the edges of the bench

A variety of router bits can be used to add edge detail to your bench. I used a 45-degree chamfer bit to route the edges on the underside of the bench, and I finished the top edge with a 1/4-inch round-over bit.

TMB STUDIO

Sand both sides of the bench

Using an orbital sander, sand the bench using 100-grit sandpaper, starting with the underside. Afterwards, move on to 120-grit, 180-grit, 220-grit, 320-grit, 400-grit, 600-grit, 800-grit, 1200-grit, 1500-grit, and finally 2000-grit.

Keep a clean microfiber towel or rag nearby while sanding to wipe off sanding dust. Use a cross-hatch sanding pattern to avoid missing any areas while sanding.

Use an air compressor to blow off dust that builds up on the sandpaper. When you reach 320 grit, begin wet sanding by spraying water onto the wood as you sand. Keep the sander moving continuously to prevent uneven sanding.

Repeat this process on all sides and edges of the bench.

TMB STUDIO

Buff and polish the epoxy

After sanding, use an air compressor, clean microfiber cloths, and cheesecloths to remove dust from the bench. Use denatured alcohol to clean off the epoxy “river”. To avoid polish penetrating the wood, cover the wood along the epoxy “river” with painter’s tape. In retrospect, I should have taped off more of the wood since small pieces of polish still made their way onto the wood and discolored it.

I polished the epoxy “river” using the 3M Perfect-It Polishing Kit, which is a three-step polishing system. To begin, use an orbital polisher fitted with a coarse foam pad and the 3m Perfect-It Rubbing Compound. Spread the rubbing compound evenly with the pad before starting the orbital polisher on a slow setting. A small amount of rubbing compound can go a long way. Increase the speed gradually while monitoring the temperature to prevent overheating the epoxy. Always wipe down the epoxy with a microfiber cloth before moving on to the next polish.

Afterwards, I repeated the process with the medium polishing pad and machine polishing compound. Then again, with the ultrafine compound and pad. Finally, I used a sperate finishing pad to apply two coats of Wizards Shine Master Polish & Sealant.

Use the same process to polish both sides of the epoxy “river.”

TMB STUDIO

Apply penetrating epoxy to the bench

Place a tarp or plastic sheeting under the bench to catch any drips. Using a penetrating epoxy (such as TotalBoat), pour and mix the resin with the hardener inside a plastic measuring cup to the amount necessary to cover the bench surface. Apply a thin layer of epoxy to the entire bench by pouring a small amount on it and spreading it evenly with a squeegee or plastic scraper. Spread it over the bench’s edges with a foam brush. Repeat the process on the other side once the penetrating epoxy has cured for two days. Remember to cover the bench with a plastic sheet to keep dust off while it cures.

TMB STUDIO

Apply final coat of clear varnish

Once the penetrating epoxy has cured, apply a marine varnish to the bench. Apply the varnish in small amounts to the bench and spread it with a foam brush or rag. Be sure to allow at least one hour between coats, and then repeat the process on the opposite side of the bench. Putting this product on the bench is essential since it is UV-resistant and can protect it from the elements.

TMB STUDIO

Install the legs

Turn the bench over on its back and determine where the legs should be placed. I placed the legs four inches from the edge of the bench. However, the leg style will determine where they should be installed. Regardless of the type of bench legs used, ensure that the legs are between 16-1/2- and 18-1/2- inches high so that the bench sits 18 to 20 inches tall including the slab. Pre-drill pilot holes with a 9/64-in. drill bit and attach the legs to the bench with #10 x 3/4-inch wood screws.

TMB STUDIO

Install the crossbeam (optional)

For this project, I bought bench legs with an opening for a crossbeam. To fit the legs, I milled a 2-1/2-in. x 2-1/2-in. beam, cut it to 44-in., and sanded all sides with an orbital sander down to 320-grit. After finishing it with the same top coat as the bench top, I slid it into the opening on the legs and secured it using a set screw from underneath.

Frequently Asked Questions

Where is the best place to pour epoxy?

Working in a space with the appropriate temperature and proper ventilation is crucial for the epoxy resin to cure correctly. It is important to note that volatile organic compounds (VOCs) are emitted during the curing process, which can be hazardous. Therefore, it is imperative to ensure proper ventilation for safety. Additionally, the optimal curing temperature range is typically between 70°F to 80°F. Always wear a mask while working with epoxy resin to ensure your safety.

How to add color to epoxy resin? 

You can add color to the epoxy resin by mixing it with the hardener in a plastic bucket during the mixing phase. Different materials can be used to color the epoxy resin, such as Alcohol Inks, Liquid Pigments, and Mica/Pigment Powders. It is important to mix them properly to avoid clumping or uneven coloring.

What type of epoxy resin do I need for a river table? 

The type of epoxy resin required depends on the particular project, and for most epoxy resin river tables, a deep pour epoxy resin is necessary. A deep pour epoxy is created to handle thick pours, two to four inches deep. Deep-pour epoxy has a thicker consistency than regular epoxy. This allows it to be poured in layers without generating too much heat.