Stain adds beauty to wood, and polyurethane protects that beauty. The combination of stain and polyurethane ensures that your wood will have appeal and longevity. The application of stain and polyurethane is routine if wood is prepared properly.
Skip the Sealer
Wood finishing is more about preparation than application. Some manufactures recommend sealer before stain or polyurethane, but it's an extra step you don't need, and it lightens the color of stain by preventing it from penetrating.
Stain highlights grain patterns. It also highlights scratches, saw marks, scuffs, dents and flaws. Remove them by sanding the wood with 120-grit sandpaper. Sand parallel with the grain only. Never sand across the grain. When it's smooth, it's ready for stain, and there are two types commonly used, oil-based and water-based.
Oil-Based Stain Traits
- Requires 72 hours or more to dry.
- Penetrates deeper than water-based.
- Doesn't clean up with soap and water.
- Won't raise grain.
Water-Based Stain Traits
- Dries in 15 to 30 minutes.
- Easy to clean up with water.
- More available colors than oil-based.
- Can raise grain.
Position yourself so that light reflects off the surface of the wood. If you see light scratches, you're not finished sanding.
Production woodworkers stop at 120-grit sandpaper, but for the smoothest finish, it's fine to resand with 180 or 220, but it's not essential. Some people continue sanding with even higher grits, up to 400, but that can result in the polishing of the wood, which causes stain to appear blotchy.
Apply the stain to the wood liberally with a sponge or soft cloth. Immediately wipe it off with a dry cloth. Work in manageable areas. If the stain begins to dry before you wipe it off, you're tackling too much area; this is more likely to happen using water-based stain. Overlapping stain on previously stained areas causes uneven colors. It's best to stain everything before stain begins to dry. If that's not possible, add stain to legs, arms, braces, panels, tabletops or individual pieces one at a time.
Apply stain to sanded scrap wood and allow it to dry. Check the color before adding it to your project. It's also advisable to add polyurethane to the stained scrap piece. Polyurethane deepens the color of stain.
Serious Stuff: Polyurethane
Polyurethane is a serious finish. Old-school, oil-based polyurethane provides the warm glow and depth associated with polyurethane. Water-based products work the same way but lack the character and color of oil-based polyurethane.
- Turns amber color with age.
- Requires between four and six hours to recoat.
- Can't be cleaned up with soap and water.
- Requires natural bristle brush for application.
- A gallon of oil-based costs about $25 at the time of publication.
- Slightly flexible to move with wood.
- Emits more fumes than water-based.
- Stays clear.
- Can be recoated in two hours.
- Cleans up with soap and water.
- Dries harder than oil-based.
- Costs about $40 per gallon, at the time of publication.
- Emits fewer fumes than oil-based.
Bubbles are common on freshly applied polyurethane. Drag your brush over them to remove them.
Polyurethane is thick and typically brushed on. Apply it in thin coats after the stain is dry.
Dip the brush about 1 inch deep into the can, and brush the wood with long, steady strokes from end to end, working parallel with the grain.
Overlap each previous stroke by about 1/2 inch, keeping a wet edge until everything's coated.
Create a clean room for applying polyurethane. Any small particles -- even dust motes or nibs, will show up in the finish.
Sand polyurethane lightly between coats with 220- or higher-grit sandpaper. You should see a fine, white powder after sanding -- if not, allow it to dry longer between coats. For the smoothest finish, wipe the surface with a sticky tack cloth before adding another coat. Two coats are sufficient for polyurethane, but you can add one or two more if desired for more depth.
Polyurethane and stain contain volatile organic compounds that can be hazardous to your health. Use it only in well-ventilated areas. Wear breathing and eye protection. Exhaust fans are recommended.