How to Hide a Hairline Guitar Crack
- 1). Remove the strings from the guitar and rest it on a solid work surface covered with an old blanket to protect the back from getting scratched.
- 2). Tape around the crack with decorators tape, leaving 1/32 inch all around to prevent excess glue spreading over the surface of your guitar. Place the flashlight inside the body of the guitar.
- 3). Place one hand inside the guitar and apply gentle pressure underneath the crack to open it slightly to make it easier to get the glue into the fissure. Work glue into the crack from above using a small artist's spatula. Use the mirror to check when the glue begins to seep through to the inside of the guitar; when this happens stop applying the glue and release the pressure from inside.
- 4). Wipe away any excess glue from inside the guitar with a damp cloth. Use a spatula to remove excess glue from the front. Leave the glue to cure for at least 24 hours.
- 5). Sand the underside of the crack to prepare for gluing in place spruce cross patches. Glue cross patches across the crack on the inside to prevent it re-opening.
- 6). Prepare enough patches to cover the length of the crack. Place them on the sticky side of a short piece of decorators tape and apply glue to the exposed wooden surface. Using your flashlight and mirror, position each patch across the crack, making sure you run the grain at right angles to the grain on the guitar body. The tape will hold it in place until you can apply bracing.
- 7). Cut lengths of dowel just longer than the space between the back of the body and the patches. Push-on pencil erasers on each end will make them easier to use and hold in position better. Carefully insert the dowels so that they hold the patches firmly in place against the underside of the crack by bracing against the inside back surface of the body. don't apply too much pressure or you may open up the crack. Allow the glue to dry before removing the dowel braces.
- 8). Touch up the finish around the crack to hide the repair. Remove the decorators tape and very gentle sand the repair with a small piece of very fine sandpaper. Lacquer is an easy product to apply and should render the repair invisible to all but the closest inspection. Apply liquid lacquer with a fine brush and let it fill the surface of the crack. The lacquer will settle into the crack so you may need to applying further coats to bring the surface of the crack right up to the level of the rest of the body. When complete apply a thin coating of spray lacquer then buff with very fine wet and dry paper.