To cover wood filler with varnish, you must first ensure the filler is completely dry, properly prepared, and then apply the varnish using standard techniques.
The crucial step before applying varnish is allowing the wood filler sufficient time to dry. According to the reference, you must allow the patch to dry overnight before applying an oil-based stain, paint, varnish, shellac or polyurethane. This overnight drying period is essential for the wood filler to cure properly and create a stable base for the varnish.
Here's a breakdown of the process:
Step-by-Step Guide
- Apply Wood Filler: Fill the desired area with wood filler according to the product instructions. Ensure the filler is slightly mounded above the surface to account for shrinkage.
- Allow Adequate Drying Time: This is the most critical step based on the provided reference. For varnish (which is typically oil-based), you must allow the patch to dry overnight. This ensures the filler is hard and ready for the next steps.
- Note: The reference mentions shorter drying times for latex paints/stains (1.5 to 2 hours), but this does not apply to varnish.
- Sand Smooth: Once the filler is completely dry (after the overnight wait), sand the patched area smooth and flush with the surrounding wood. Start with a medium-grit sandpaper and finish with a fine-grit sandpaper (e.g., 150-220 grit) for a smooth finish that will accept varnish well. Remove all dust.
- Apply Varnish: Apply the varnish following the manufacturer's instructions. This usually involves:
- Stirring the varnish (do not shake).
- Applying thin, even coats with a quality brush, foam applicator, or spray gun.
- Following recommended drying times between coats.
- Lightly sanding between coats if recommended by the varnish product.
- Apply Multiple Coats: Most projects require multiple coats of varnish for durability and depth.
Drying Times at a Glance
Based on the reference, here's a quick look at recommended drying times for wood filler before applying different finishes:
| Finish Type | Minimum Drying Time for Filler |
|---|---|
| Oil-Based Varnish, Stain, etc. | Overnight |
| Latex Paint or Stain | 1.5 to 2 hours |
Ensuring the filler is fully dry before varnishing prevents issues like cracking, shrinking, or poor adhesion of the varnish layer. Always check the specific wood filler product's instructions for any additional guidance or variations in drying times.
