It is important to avoid using a high-pile roller, as it can leave excess material on the surface and can cause air bubbles. For a smooth finish with even coverage, use overlapping roller strokes and use a brush to manoeuvre around corners and details. After the varnish is applied, it should be left to cure.
Varnish should always be applied with a brush. You may want to very slightly add a bit of water, just a small amount, for the first coat to avoid brush marks and then apply a few coats at full strength to seal and protect the piece. I'd recommend a good quality water-based acrylic varnish using a soft brush.
For any varnish application over a smooth, even surface (tabletops, dressers, cabinets, etc) my go-to tool is a simple sponge. I love the orange sponges you can find in the automotive detailing department or a good grout sponge.
You can simply wipe on thinned varnish with a rag or you can even spray it. But when I want all the benefits that varnish has to offer, I apply it the tried-andtrue way — with a brush. Several coats of brushed varnish will produce a smooth, classic look along with all the protection a truly firstrate project deserves.
Sanding and reapplying varnish for a smooth finish
Sanding and reapplying varnish can give your furniture a smooth and professional finish. To achieve this, begin by sanding the wood to remove any imperfections and old varnish. Once the surface is smooth, apply a new coat of varnish evenly, using long, smooth strokes.
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.
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.
For a very durable finish and one that needs to be very tough, say on a kitchen table, coffee table or end table etc, 2 to 3 coats of varnish should be enough on the top, with 1 to 2 coats on the legs/base. For chairs, benches, chests and other such pieces, 1 to 2 coats should do the trick.
Natural bristle is the best choice for oil-based paints, varnishes, shellac, alkyd enamels, oil stains and oil-based polyurethanes. The highest quality bristles come from mainland China. Experienced, traditional painters will say there's nothing like the finish that a China bristle can provide for oil-based coatings.
Shellac. Shellac is a very widely used single-component resin varnish that is alcohol-soluble. It is not used for outdoor surfaces or where it will come into repeated contact with water, such as around a sink or bathtub.
Avoid shaking the varnish too vigorously before applying and let it rest for at least 15 minutes. Make sure to leave enough time between each coat to allow the varnish to dry properly. Clean the surface well before applying varnish, as dirt and dust can also cause bubbles.
Using a brush––usually a China bristle brush attached to a long pole––is the recommended application method for conversion varnish (also known as Swedish or acid cure finishes). Brushes are also commonly used to apply oil-based and moisture-cured polyurethane finishes.
Paintbrushes can provide a certain texture and finish that you won't be able to achieve with a roller. If you're hoping to add a personal touch or give your painting project a more rustic look, then going with paintbrushes might be the way to go.
The proper preparation procedures (fixing, sanding, and cleaning) should be performed before applying varnish to ensure a successful and long-lasting bond between the surface and the varnish.
It is important to avoid using a high-pile roller, as it can leave excess material on the surface and can cause air bubbles. For a smooth finish with even coverage, use overlapping roller strokes and use a brush to manoeuvre around corners and details. After the varnish is applied, it should be left to cure.
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.
Traditional oil-based varnishes are more durable than water-based alternatives. They can cope better with temperature variations, so they're more suitable for use on exterior wood. Oil-based varnish takes longer to dry and is best applied with a natural bristle brush.
If you plan on removing the varnish and then painting the wood, sanding can be an effective way to get rid of the varnish while prepping the wood at the same time. It's also a natural and chemical-free way to remove varnish. It can however be labour-intensive: Start with 150-grit sandpaper and sand the entire surface.
Finish by drawing the brush from the wet area to the dry along the grain. Reload the brush and apply varnish to the next section of wood, 'landing' the brush just into the end of the wet edge. Repeat the process until you reach the end of whatever you're varnishing.
Waterborne polyurethanes usually require a minimum of 3-4 coats to be effective. Although there is some evidence that too many coats can result in a plastic-like finish, waterborne polyesters are thinner than other types and therefore require several more coats to provide the same protection for hardwood floors.
To varnish, lay a coat down, slightly overlapping the brush strokes to get an even application. Then apply again the opposite way, this will make sure you get the best coverage and an even application. Then allow it to dry completely.
Wipe off any excess paint using a cloth or soft tissue. Squeeze the bristles gently from the ferrule edge outwards, being careful to avoid pulling on the bristles. If you've been using oil, rinse the brush in turpentine or brush cleaner. If you've been using a water-based medium, lukewarm water will do.