How To Fill Wood Voids with Epoxy

First, this article is part of a the DIY walnut epoxy dining table build series.

I incorporate unique and reclaimed wood in most of my woodworking projects.

Many of these live edge wood slabs have structural issues that need to be addressed before I can use them for furniture. As a result, I use epoxy to repair large wood voids as well as a burn-in stick for smaller wood defects.

Epoxy works great for filling knots, cracks, voids and other wood defects as it repairs and stabilizes rotted wood.

My 2 step technique I use in this project shows you how to fill wood knots with epoxy correctly.

Although I used clear epoxy in this project, I often use colored epoxy, glow powder, or turquoise to fill cracks in wood.

Prepare Surface Area

I prepared the surface area before I fillled wood defects with epoxy to ensure proper adhesion.

First, I rough sanded the surface with low grit sandpaper to expose small holes, cracks, and other wood defects.

Rough sanding removes much of the dirt and debris which hide wood defects.

Next, I loosened the debris with various tools and vacuum them up from within the wood voids.

Ultimately, proper surface preparation is key to successfully fill voids in wood with epoxy.

Seal Underside of Wood

In my experience with various wood species and live edge slabs, I find most wood defects extend to the underside of the wood.

Also, all large voids in wood extend to the underside of the wood.

As a result, I sealed the underside of the table with tuck tape (any sheathing tape works) to prevent epoxy leaks.

Best Epoxy for Filling Voids in Wood

As I mentioned, I use a 2 step process to properly fill defects in wood with epoxy.

My 2 step process consists of using different types of epoxy.

I use deep pour epoxy for the first step, which is mixed at a 2:1 ratio.

For the second step, I use an epoxy with a 1:1 mixing ratio. This epoxy normally cures within 24 hours.

Deep Pour Epoxy

For the first step, I used deep pour epoxy to partially fill the wood voids.

As I outlined in my best epoxy resin for wood projects, I use chill epoxy and liquid glass as my preferred deep pour epoxy.

Deep pour epoxy penetrates and seals very well which allows it to fill all voids and soak into the wood fibers.

In addition, it cures slowly which makes for a stronger bond.

For the second layer, I used a table top epoxy resin with a 1:1 mixing ratio. This resin cures quickly and thicker than deep pour epoxy.

Fill Wood Voids with Epoxy

First, I filled the cracks, knots, and voids with deep pour epoxy.

I allowed the epoxy soak in for a few minutes and added more until the wood void was half full with epoxy.

As a quick tip: Some wood voids require more epoxy than others so be sure to keep an eye on it after you pour.

The purpose of the first epoxy layer is to penetrate and seal the wood. In turn, I poured enough to partially fill the holes.

Remove Epoxy Air Bubbles

Next, I used a mini torch to heat the resin for even better penetration and to remove air bubbles.

Then, I allowed the deep pour epoxy to cure for 24 hours.

A 24 hour cure time allows the epoxy to partially cure and adhere to the next epoxy layer.

2nd Epoxy Layer

I used total boat table top epoxy to fill the wood voids, cracks, and knots.

To avoid unnecessary sanding, I filled the wood void until it reached the wood surface. I allowed it to soak for a few minutes and poured more if needed.

Ultimately, I needed to pour an epoxy river and flatten the walnut dining table.

So, I wasn’t too concerned with the epoxy overflowing.

Once the epoxy dried, I poured a blue epoxy river, flattened the wood slab table with my router, and sanded the table smooth.

These steps were part of the DIY Walnut Slab Dining Table full build.

Use Burn-In Stick for Small Holes

After I flattened and planed the table, I noticed a few tiny holes near the wood knots, cracks, and voids.

So, I used a burn-in stick to fill them. I only use a burn-in stick for small wood voids.

filling holes in wood with burn in stick

First, I adjusted the flame on my mini torch to low.

Next, I applied heat to the burn-in stick until it became soft.

Then, I smeared the soft part of the burn-in stick to fill the small wood voids.

I repeated this process until there were no voids remaining on the table.

As a final step, I removed the excess with my card scraper.

When the wood shavings produced by the card scraper change colors, I know the excess is gone.