How To Fill Wood Voids with Epoxy

In this step-by-step guide, I show you how to fill wood voids with epoxy resin. Learn the best epoxy wood filler and many more helpful tips.

In fact, I use these wood repair techniques on beautiful pieces of wood for client projects. These wood defects include wood voids, checks, knots, cracks, and large holes.

The tips and techniques covered in this tutorial can be used on any piece of wood for long-lasting repairs. So, keep reading to learn the best way to fill wood knots with epoxy for the best results on wood projects.

Tools and Materials

Deep Pour Epoxy
Penetrating Epoxy
Epoxy Resin (Fast Curing)
Mini Torch
Card Scraper
Burn In Stick
Rotex Sander
Vacuum
Router
Router Slab Flattening Bit
Epoxy Wood Putty
Hardwax Finish
Tuck Tape

Video Tutorial

There are several things which are difficult to fully explain with words and images, so be sure to check out the video tutorial below!

What Type of Epoxy Fills Voids in Wood?

The 2 types of epoxy used to fill wood voids are liquid epoxy and epoxy wood putty.

Liquid Epoxy vs Epoxy Wood Filler

This article focuses on using a liquid wood filler to fill wood voids. However, wood epoxy putty is another great option.

Choosing right product and the best wood filler largely depends on the size of the wood defect.

Liquid Epoxy

Liquid epoxy works best to fill large gaps, large cracks, and larger voids in wood. Keep in mind, low-viscosity is the best epoxy to fill wood voids.

The liquid reaches the bottom of the hole, soaks into the wood fibers, and the long curing process creates a strong bond. Additionally, pigments and dyes can be added to the epoxy to create a variety of colors.

Epoxy Wood Filler (Putty Version)

Epoxy putty is a great option for filling small holes and smaller voids in wood. It creates a durable bond and cures very quickly.

My favorite epoxy wood putty is TotalBoat Thixo Fast Cure. Also, you can use dyes to color this epoxy putty.

Best Epoxy for Filling Voids in Wood

As previously mentioned, low viscosity epoxy is the best epoxy for filling wood voids and larger holes.

This epoxy is often referred to as deep pour epoxy or penetrating epoxy. Often times, the marine industry uses this epoxy for boat building and wooden boat restoration as it seals and stabilizes rotted wood.

My favorite liquid epoxy to use to fill wood voids is TotalBoat Penetrating Epoxy while my favorite deep pour epoxy is Liquid Glass 2.0.

Prepare Surface of the Wood

Rotex Sander
Vacuum
Tuck Tape

Obviously, it is a good idea to prepare the surface of the wood before adding an epoxy filler.

First, rough sand the wood 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, loosen debris inside the wood void and remove with a vacuum. Keep in mind, proper surface preparation is key to filling wood voids with epoxy.

Seal Underside of Wood

Regardless of the wood species, most large voids and wood cracks extend to the underside of the live edge slab.

In turn, use sheathing tape to seal the underside of the wood to prevent leaks. The tape forces the epoxy to pool at the bottom of the wood void instead of leaking on the floor.

Fill Wood Voids with Epoxy

Deep Pour Epoxy
Penetrating Epoxy
Mini Torch

First, mix the epoxy in small batches in order to minimize waste. Since deep pour epoxy and penetrating epoxy cures slowly, you have plenty time to mix more epoxy if needed.

For the next step, slowly pour the epoxy to fill the wood void with resin.

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

As a quick tip, monitor the slab closely after you pour the first batch of epoxy. Some wood voids run the length of the wood slab with various exit points.

Keep in mind, you don’t need to completely fill the wood void completely with the first pour.

Remove Epoxy Air Bubbles

Mini Torch

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

Then, allow 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.

Additional Epoxy Layers

Deep Pour Epoxy
Penetrating Epoxy
Mini Torch

If you didn’t completely fill the wood void in step 2, mix and pour additional resin until you completely fill the wood void with epoxy. Since the first epoxy layer sealed the wood void, the subsequent epoxy layer should fill it completely.

To avoid unnecessary sanding, I fill the wood void until it reaches the wood surface.
Allow the epoxy to make it’s way down the wood void for a few minutes and poured more if needed.

Try your best to avoid pouring too much epoxy. The excess will overflow the wood void and increase sanding time to get a smooth surface.

Filling Wood Cracks with Colored Epoxy

Epoxy Glow Powder
Best Epoxy Pigment Powder

If you want to add a unique feature to your project, fill the wood cracks with colored epoxy or glow in the dark powder. Not only will this fill the wood voids, but it will also eliminate the wood defect altogether.

First, choose the color pigment or glow powder.

Next, add the pigment to the resin and mix together. Keep in mind, only add it after the epoxy resin is thoroughly mixed.

Finally, fill the wood crack with colored epoxy.

Flatten and Sand Wood

Deep Pour Epoxy
Mini Torch
Rotex Sander
Vacuum
Router
Router Slab Flattening Bit

Once you fill the wood void with epoxy, proceed with the rest of your project.
The steps below are part of the DIY Walnut Slab Dining Table project.

How To Use Burn-In Stick for Small Holes

Mini Torch
Card Scraper
Burn In Stick

After you sand the table, you may notice a few tiny holes near the wood knots.

So, use a burn-in stick to fill the tiny holes.
Also, burn-in sticks comes in various colors to match most wood species.

First, adjust the flame on the mini torch to low.

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

Then, smear the soft part of the burn-in stick to fill the small wood voids.
Repeat this process until there are no voids remaining on the table.

As a final step, remove the excess with a card scraper. Essentially, the card scraper should leave a smooth finish.

The excess is gone when the wood shavings produced by the card scraper change colors.

Apply Wood Finish

Hardwax Finish

As a final step, apply the epoxy wood finish of your choice.

I wrote an article about finishing epoxy wood surfaces, so be sure to check that out.

Final Thoughts

Whether you use new wood or reclaimed wood in your woodworking projects, there is a good chance you will need to fill wood voids with epoxy.
I hope the simple steps in this article help you achieve the best results possible.

Related Posts

• DIY Walnut Epoxy Dining Table
• Simple Resin Calculator
• Best Epoxy Resin for DIY projects
• 11 Best Epoxy Tips You Need to Know

Frequently Asked Questions