Whether you purchased unfinished kitchen cabinets or you want to rejuvenate the finish on existing wood cabinets, applying varnish is a necessary step for a rich, washable finish. Modern water-based acrylic varnish makes it possible for you to do this job over the weekend. Unlike oil-based varnish, acrylic varnish is low odour and dries quickly so you can apply two coats in one day. If you've stained the cabinets, wait at least 24 hours before applying varnish. If you opt for a natural wood, unstained look, all you need to do is clean and sand the wood first.
Remove the cabinet doors, drawers and hardware with a screwdriver or screw gun. Put hinges, knobs and screws in a bucket so they don't get misplaced.
Set up a work area, such as boards laid across saw horses or 5-gallon buckets, for the doors and drawers. Choose a dust-free, warm place such as a garage or basement.
Protect the floor and counter tops below the kitchen cabinet boxes with dust sheets or newspaper taped down to hold it in place.
Sand unstained wood with a sanding sponge, working with the grain of the wood. Pay particular attention to edges and detailing to remove rough spots and small slivers of wood. If the cabinets are already stained and in good condition, skip this step.
Vacuum or brush away the sanding dust, then wipe all surfaces down with a tack cloth to remove every last bit of dust.
Apply a coat of acrylic varnish with a high-quality 2- or 3-inch brush. Allow it to dry for at least four hours, then sand it lightly with a sanding sponge or 220-grit sandpaper. Remove the dust with the tack cloth.
Apply at least two more coats of varnish to the cabinets, always brushing with the grain of the wood instead of across it. If you sanded and dusted thoroughly after the first coat, you may not have to sand between subsequent coats. Work in a strong light and run your hand over the surface to feel for rough spots.
Allow the cabinet doors to dry for about 24 hours before hanging them; the varnish will be slightly soft and you risk scratching the finish if you handle the doors too soon.
Don't be alarmed when the acrylic varnish looks milky-white when first applied. It will dry crystal clear. Apply thin, even coats of varnish instead of trying to get away with fewer, thick coats. Applying varnish too thickly leads to runs and an uneven surface. Apply the final coat of varnish to the fronts of the doors after you've reinstalled them, and leave the doors and drawers slightly open for about 24 hours to allow them to dry fully.
Don't use a cheap brush or a roller for applying varnish. A cheap brush will leave visible brush marks and a roller will create small bubbles in the finish, which are very hard to sand out. Avoid washing varnished cabinets for about 30 days. The varnish takes about that long to become fully cured and hard.