How to Fill Burl Voids and Cracks with Epoxy: A Step-by-Step Guide

Filling burl voids with epoxy is basically about getting all the loose dust out, sealing the underside maybe with tape or hot glue, then adding the epoxy in thin layers, like a deep pour but controlled, so it doesn’t overheat or start cracking. Each layer must be cured before the next layer can be applied, and then flattened and sanded when the epoxy has cured. If done properly, this will result in a glass-like characteristic of the voided wood.

Why Do Burls Have So Many Voids and Cracks?

Tree burls are an irregular swirl that forms on either the roots, trunk, or branches of trees. They occur due to the tree being subjected to stress, pests or fungus infections. The grain in a burl tends to twist and fold as opposed to flowing straight resulting in the bark becoming trapped within the wood as it forms. Additionally, drying out of the outer fibers becomes uneven. This is the reason why tree burls tend to have voids, bark inclusions, and stress cracks after drying and turning.

These openings aren’t really a defect to work around, they’re part of what makes burl wood so collectible. When you fill the burl voids with epoxy it helps stabilize the piece, kind of structurally, while also bringing out that same swirling grain which is what makes exotic hardwoods like burl so in demand, especially for turners and furniture makers.

What Materials Do You Need to Fill Burl Voids with Epoxy?

Before you start mixing anything, make sure that all of the following are at hand. Because burl voids always appear deeper than one might think, over-preparation is always better than stopping halfway through pouring.

How to Fill Burl Voids with Epoxy: Step-by-Step

1. Clean out the void. Remove loose bark, dust, and punky wood with a pick or small brush so the epoxy bonds to solid material.

2. Seal the bottom side. Cover any holes that run through the surface with painter’s tape or hot glue on the reverse side to avoid leaks.

3. Dry-fit and dam the edges. In the case of open bowl blanks or slabs, use tape to create a boundary to ensure the epoxy is restricted to the designated areas.

4. Measure out the resin and hardener by weight. Be precise when measuring, using a digital scale in place of measuring by volume.

5. Pour in thin layers. Apply thick epoxy in thin layers of 1/4 to 1/2 inches for larger voids instead of pouring everything at once, allowing enough time between layers for the previous layer to gel.

6. Remove bubbles. Pass a heat gun lightly over the surface right after pouring to pop trapped air.

7. Cure completely before machining. Most epoxy castings take 24-72 hours to harden enough to turn, and even up to two weeks to cure completely.

8. Flatten and sand. After the epoxy has cured, sand it down flush with the rest of the burl wood, moving through the grits to finish.

Deep-Pour Epoxy vs. Standard Tabletop Epoxy: Which Should You Use?

What Mistakes Should You Avoid When Filling Burl Voids?

• Pouring a deep void in one shot, which traps heat and can crack the epoxy or the surrounding wood.

• No need for the weight calculation; just look at the proportions between resin and hardener.

• Turning or sanding before the epoxy has fully cured, which tears the fill instead of cutting it clean.

• Ignoring punky or soft sections around a void, epoxy bonds better to solid wood than to decayed fiber.

• Using a standard tabletop epoxy for a deep void instead of a deep-pour formula rated for it.

Where to Find High-Quality Burl Wood for Epoxy Projects

The result of an epoxy fill depends as much on the starting material as the technique. Well-dried burl wood with clean grain around its voids fills more predictably than green or punky stock. At Exotic Wood Zone, our burl bowl blanks, burl pepper mill blanks, and other turning blanks are hand-selected and properly dried, so the voids and cracks you're filling are a feature of the exotic hardwoods, not a symptom of poor drying or storage.

Whether you're working on a single feature bowl or stocking up on turning blanks for a season of projects, choosing burls sourced from a specialist in exotic woods will provide you with a more stable foundation for working with epoxy from the start to the finish.

FAQs About Filling Burl Voids with Epoxy

1. Can you fill burl wood cracks with epoxy while the wood is still wet?
   It is advisable to dry burl wood to a point where moisture levels are stable. Applying epoxy in wood that is still wet can trap the moisture in the wood thus causing the fill to fail and cracking to occur later on in the wood around the fill.

2. How long does epoxy take to cure in a burl void?
   The majority of deep pour epoxies can be handled in 24 to 72 hours after curing and hardening. However, complete curing may require about two weeks so allow more time for large pour applications before machining.

3. What's the best epoxy for filling burl bowl blanks?
   Deep pour or casting epoxy should be used on burl bowl blanks because this type of epoxy takes longer to cure than table-top epoxy and produces less heat.

4. Do I need to stabilize a burl blank before filling it with epoxy?
   Not always. Stabilization is most useful for punky or soft burl wood, where resin is vacuum-infused through the whole piece. Solid burl with isolated voids can usually go straight to a targeted epoxy fill.

5. Why did my epoxy fill crack after curing?
   The crack is definitely caused by pouring too much epoxy all at once, leading to increased exothermic heat. Thin, sequential layers are the fix.

Conclusion: Turning Burl Voids into a Feature, Not a Flaw

The task of filling burl voids using epoxy requires more patience than skill: prepare the hole, cover the back, make accurate mixing, and put it in thin layers for a controllable curing process. In other words, prepare the hole, use deep pouring epoxy for anything larger than half an inch, pour in layers, and do not rush the curing process before sanding or turning. Get yourself good, dried burl wood and the epoxy filling will emphasize its grain rather than fight with it. Explore Exotic Wood Zone's selection of burl bowl blanks, burl pepper mill blanks, and other exotic hardwood turning blanks to find your next project piece.