Most refinishing problems come from one of three things: contaminated surfaces, sanding or stain choices that don’t suit the wood, or rushing the drying steps. Most of them are easy to prevent once you know what to look for.
Fisheyes and craters
Fisheyes are small round craters that appear in a finish as it dries. They usually come from silicone or wax residue on the wood. Silicone is in many furniture polishes, lubricants and skin-care products, so it often ends up on old furniture without anyone noticing.
To prevent fisheyes, clean the bare wood with mineral spirits or naphtha before you finish. In a stubborn case, a coat of dewaxed shellac can seal the contamination underneath. Once fisheyes have formed, the usual fix is to wash the finish off with the right solvent and start again.
How to clean old wood furniture before refinishing explains the cleaning order.
Blotchy stain
Pine, cherry, maple and birch are prone to blotching, where stain soaks in unevenly and leaves dark and light patches. Uneven density in the wood is one cause. Stain that is not wiped off in time is another.
Use a pre-stain conditioner or a thin washcoat of shellac on these woods. Oak rarely blotches and usually doesn’t need one, which is covered in oak furniture restoration tips. Wipe off the excess stain before it begins to dry, and don’t leave it on longer than the label says.
Blushing in humid weather
Blushing is a milky, cloudy look that appears in fast-drying shellac and lacquer when the air is humid. Moisture condenses on the surface as the solvents evaporate. Varnish and water-based finishes don’t usually blush.
Lacquer and shellac blush more when humidity is high, roughly above 80 to 85 percent, though the threshold varies. Adding a retarder slows drying and can help, but use only as much as you need. Blushing sometimes clears on its own. Otherwise, let the finish harden and rub it out with a fine abrasive.
Swirl marks and sanding too fine
Swirl marks are circular scratches left by a random-orbit sander, often from skipping grits or pressing too hard. Finish by hand with the grain at your final grit to remove them.
Sanding too finely before stain is another common mistake. Going much past 220 grit on many hardwoods can burnish the surface, closing the pores so the stain can’t soak in evenly. What grit sandpaper to use on wood furniture gives a full grit guide.
Bubbles, dust nibs and runs
- Bubbles in polyurethane. Stir the finish rather than shaking it, apply thin coats, and don’t overbrush.
- Dust nibs. Clean the work area before you finish. Between coats, remove dust and sand lightly with 320 to 400 grit. Tack cloths can leave residue under some water-based finishes, so a damp microfiber cloth is often safer.
- Runs and sags. Thick coats cause runs and slow curing. Several thin coats work better than one heavy one.
Recoating too soon
Recoating before the previous coat has cured can leave a finish that is soft, wrinkled or sticky. Follow the recoat times on the label. Rushing is one of the most common reasons a refinish fails, even when every other step is done well.
Temperature matters too. Many finishes cure poorly below about 50°F (10°C). The ideal range for finishing is roughly 65 to 75°F (18 to 24°C), and the product label has the final word.
Stripper residue and sand-through
Leftover stripper can stop the new finish from curing. Clean it off as the label directs before you finish. On veneer, sanding through the thin top layer is a common accident, especially on edges and corners. If it happens, the area usually needs patching and refinishing, as covered in how to restore a veneer furniture surface. How to tell solid wood from veneer furniture helps you check before you sand.
A prevention checklist
- Clean the surface and remove silicone and wax.
- Test the stain on a hidden area.
- Keep your grit progression in order.
- Wipe off excess stain in time.
- Check the humidity and temperature before you finish.
- Follow the recoat times on the label.
- Remove dust between coats.
Safety: oily rags left in a pile can catch fire. Dry them flat outdoors or store them in water in a sealed metal can.