Wood is full of tiny pores filled with air. When warm, liquid epoxy flows over it, that air escapes upward and leaves bubbles in your finish. A thin seal coat fixes that before the main pour.
Key takeaways
- A seal coat is a thin layer of epoxy brushed or spread into the wood first.
- Start with dry, clean, sanded wood.
- Do the flood coat or main pour within your epoxy’s recoat window.
Step 1: Prep the wood
- Dry wood only. Moisture trapped in wood can cause cloudiness and adhesion problems. Use a moisture meter and follow your resin maker’s guidance for acceptable moisture levels.
- Remove bark and loose material on live-edge slabs, or seal the bark well if you keep it.
- Sand the surface (for example to 120-180 grit) and remove all dust with a vacuum and a clean, lint-free cloth. Avoid silicone-based tack cloths.
Step 2: Apply the seal coat
- Mix a small batch of epoxy carefully. See how to mix epoxy.
- Brush or spread it on thinly with a foam brush or plastic spreader, working it into the grain, cracks, end grain and knots.
- Use a heat gun or torch lightly to bring up bubbles, keeping it moving and away from the wood. Never hold heat in one spot.
- Check after a few minutes for new bubbles. Porous areas may need a second thin coat.
Step 3: Time the next coat
Let the seal coat firm up, then apply the flood coat or main pour within the window your product’s instructions give for a chemical bond. If you miss it, the seal coat may need to be lightly sanded first so the next coat sticks. Watch for amine blush with some products in cool, humid conditions.
Common mistakes
- Sealing in a cold garage that’s warming up during the day. Rising temperatures make trapped air expand. Work when the temperature is steady or slowly dropping.
- Seal coats that are too thick, which can trap bubbles themselves.
- Skipping the end grain, which soaks up the most resin.
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Header image: Photo: “WOOD SLABS TABLE” by IndoGemstone, BY 2.0 (cropped).