Applying finish to vertical surfaces requires different techniques than flat panels. Runs and drips ruin otherwise clean work.
Thin Your Finish
Reduce most finishes by 10-15% with the appropriate thinner. For oil-based polyurethane, use mineral spirits. Water-based finishes thin with distilled water.
Thinner coats dry faster and flow better. Multiple thin coats outperform one thick application every time.
Work From Bottom to Top
Start at the bottom of vertical surfaces and work upward. Any drips that form fall onto wet finish and blend in naturally.
Keep a dry brush handy for catching runs. Check your work from a raking angle to spot issues before they set.
Control Temperature
Finish vertical work in cooler conditions when possible. Cold finish flows slower and gives you more working time. Avoid direct sunlight that causes fast drying and traps solvent.
Consider Your Options
Wipe-on finishes work well for vertical surfaces. Arm-R-Seal, thinned polyurethane, or Danish oil apply easily with minimal drip risk.
Spray finishes also solve the gravity problem but require more equipment and ventilation.
For large vertical panels, consider finishing horizontally when possible. A door on sawhorses receives finish more easily than mounted in its frame.
