But when it comes to applying a smooth coat of clear finish, such as polyurethane, a foam brush is not my first choice. Instead of bristles, it has a blade. The blunt sides leave two parallel ridges of finish, like a snowplow on the highway. Also, the foam head contains air, which can leave bubbles in your finish.
DO NOT USE A BRUSH! You can solve the majority of polyurethane top coat applications by simply using a foam paint roller! I like to also follow up with a small foam paint brush so that I can easily get into the cracks and crevices and all the little details.
Use synthetic bristle brushes for jobs that require latex and acrylic paints. These brushes are also best for use with thin products, like stain or polyurethane finishes. Foam brushes are great for painting window casings and moldings because they provide a smooth, stroke-free finish.
Just about every professional varnish applicator will cringe at the thought, but many will say a foam brush will be suitable on the sealer coats or on some build coats—but the final coats should always be with a high-quality, natural bristle brush.
But when it comes to applying a smooth coat of clear finish, such as polyurethane, a foam brush is not my first choice. Instead of bristles, it has a blade. The blunt sides leave two parallel ridges of finish, like a snowplow on the highway. Also, the foam head contains air, which can leave bubbles in your finish.
Sand the surface smooth and flat before applying the final coat. Do your best to eliminate all the dust you can for this last coat. If you have done everything else well, your finish will look great even with a little dust. If the remaining dust bothers you, buff it out later.
Foam brushes don't do a better job of laying out varnish on surfaces than do bristle brushes. But they don't do a worse job, either. Sure, expensive bristle brushes allow you to spread the varnish out smoothly, but so does a forty nine cent foam brush.
While natural bristle or bristle-and-synthetic blend brushes are recommended for oil-based products, synthetic brushes, including foam brushes, are better for water-based varnishes. These polyurethane foam brushes are ideal for craft projects or small-format jobs, and their price makes them a good option for educators.
Before use, a can of polyurethane should be stirred, not shaken. Shaking can introduce air bubbles in the finish that could make an uneven coat. Minimize or eliminate brush marks. Choose a tapered brush, thin the varnish with mineral spirits and apply long strokes at a vertical angle.
Prepare the polyurethane by reducing it about 10 percent with mineral spirits, unless you're using water-based polyurethane, which doesn't need thinning. Thinning the polyurethane makes it flow on more smoothly and reduces brush marks. Quick Tip!
Two coats of finish are suggested for most interior projects. When sealing floors, you should apply three coats. However, do not apply more than two coats in one day. 220 grit sandpaper should be used between coats to remove any air bubbles, but avoid using steel wool.
Purdy® White Bristle paintbrushes are made with a soft, natural bristle blend that provide an ultra-smooth finish. These brushes are best for oil-based stains, polyurethanes, wood thinners, lacquer thinners and clears. Designed with lightweight and moisture-wicking alderwood handles, this painting tool is made to last.
For oil-based polyurethane, never wet the brush with water, as this can cause adhesion issues. The key is to use a high-quality, dry brush and apply the polyurethane in thin, even coats, allowing each coat to dry thoroughly and sanding lightly between coats for the best results.
If you're short on time, here's a quick overview: Composition: Polycrylic is water-based, while polyurethane can be oil-based or water-based. Application: Polycrylic applies in thin coats and dries quickly; polyurethane takes longer to dry.
Synthetic-bristle brushes are the most common option. The bristles are made with synthetic material, like nylon or polyester, which is better for applying water-based polyurethane for floors, walls, and other surfaces. Synthetic brushes are also frequently used with latex-based paints.
Brush on a coat of varnish; hold the brush at a right angle 10° to the surface; and, working in the direction of the grain, lightly skim the varnish with the bristle tips to help level it.
Clear varnishes should always be applied by brush. Applying paint by roller is fast and easy, but be ware! Application by roller leads to much thinner coats than application by brush (up to 50% less). Therefore always apply one or more additional coats when applying paint by roller.
Foam brushes are usually of poly construction, and are commonly safe for most one-part paints, primers, and varnishes. However, some two-part urethane or epoxy systems can contain solvents or chemicals that will destroy a foam brush.
To keep from damaging your varnish brush, stick to dish soap and water. Wash the brush with dish soap under warm running water. Rub dish soap into the brush bristles and work it into a lather.
Sanding Tips: No sanding is needed if you overcoat within 48 hours. Don't sand unless the most recent coat has dried for 24 hours. Use 320 grit to prevent scratches; sandpaper finer than 320 grit will not allow proper adhesion. Remove residue before reapplying.
Proper varnish application is key to achieving a smooth and even result. This can be done by starting with a clean surface, applying thin coats, and sanding in between layers. It is also important to avoid common mistakes and issues, such as overloading the brush or not allowing enough drying time between coats.