Nitrocellulose lacquer is the most commonly used finishing product for guitar as well as other musical instruments. It provides a strong and durable finish and it is also available in a large array of colours. It available in aerosol spray which makes its application relatively simple and easy. Applying the lacquer is a two-step procedure. The first step involves prepping the guitar and the second step involves applying a sanding sealer and two coats of lacquer. Although the process is not difficult, it does require patience and an eye for detail.
Sand the guitar with 100- to 120-grit sandpaper. The goal is to make the surface smooth so the lacquer adheres better to the wood. Sand in the direction of the grain. Once the surface feels smooth to the touch, sand the guitar one more time with 150- to 170-grit sandpaper.
Wipe the guitar with a soft cloth to remove the sanding dust. Wet a piece of fine grit sand paper and go over the guitar one more time to remove fingerprints and other oily residues on the guitar.
Apply a coat of sanding sealer to the guitar. Sanding sealer is available in aerosol spray cans at woodworking and hardware stores. The sealer prepares the surface of the guitar for the lacquer topcoat. Hold the nozzle eight inches above the guitar and apply a smooth even coat. Sand the guitar with light-grit sandpaper after the sealer has completely dried.
Suspend the guitar from the ceiling with a couple strings. Place a tarp under the guitar to protect the floor or workbench from overspray. Suspending the guitar makes it easy to apply the lacquer on the front, back and sides.
Apply one coat of guitar lacquer to the guitar. Guitar lacquer is available in aerosol spray in a variety of guitar colours from Stewart MacDonald [go online to stewmac.com], a luthier's supply company. Hold the nozzle eight inches from the guitar and spray a light coat of lacquer. Applying a light coat prevents drips, runs and heavy spots from building up on the guitar. Allow the first coat to completely dry. Lightly sand the finish with fine-grit sandpaper until the surface feels smooth to the touch.
Apply a second coat to the guitar. The chemicals in the lacquer break down when the second coat is applied so that the second coat blends into the first coat. The result is a strong durable coat rather than different layers. Allow the second coat to completely dry.