How to Stain Fir Window Trim

Sand the trim to create an even and smooth surface. Start sanding with a 120-grit sandpaper and finish it with a 220-grit sandpaper. Sand in the direction of the wood grain.

Wipe down your trim with a rag dampened with water if your stain is water-based or mineral spirits if your stain is oil-based.

Condition the wood to help block some of the wood pores. This will ensure a uniform appearance when the stain is applied. Use a water-based conditioner if you are applying a water-based stain or an oil-based conditioner if you have selected an oil-based stain. Paint the conditioner in the direction of the wood grain. Follow the directions on the can for further application instructions and drying time.

Apply an even coat of stain in the direction of the wood grain with a brush or rag and rub the stain into the wood with a rag. Allow the stain to sit on the trim for 30 seconds.

Wipe off any excess stain in the direction of the wood grain with a clean, dry rag, pressing only lightly.

Allow the stain to dry for at least four hours, applying additional coats as necessary.

Apply a finish sealer. Use a polyurethane sealer if you used an oil-based stain or a water-based sealer if you used a water-based stain. Paint on the sealer following the instructions on the can for further application instructions and dry-time. Apply at least three coats or until the desired sheen is achieved. Always allow each coat to dry before applying another. Sand between coats with a 220-grit sandpaper.