Internal guitar wiring acts like antenna, intercepting extraneous signals from ordinary electronic devices such as televisions, radios, cell phones or even the Internet. The signals travel from the guitar's wiring straight out through your amp where they are amplified into a hum or a buzz. Most guitars have internal shielding but some don't. If your guitar hums consistently when you're not playing it, you might need to shield it. Do it in a few minutes with aluminium foil.
Remove the strings from the guitar. On Gibson guitars, unscrew and remove the two plastic retainer rings around the pickups using a screwdriver and then remove the two screws that hold each pickup to the body. Lift the pickups out and let them hang by their wires. On Fender guitars, remove all the screws that hold on the full body pick guard. Lift it off and turn it upside down to expose the pickup cavities.
Turn the guitar upside down and remove all the screws that hold on the plastic control cavity, then remove the cavity. This is the same method for both Gibson and Fender guitars.
Use your fingers to push one section of foil down into each of the pickup cavities. Form the foil to the shape of the cavity by forcing it into the corners and moulding it to the bottom, sides and around the wires. Trim off the excess foil with scissors.
Lift up the moulded foil and gently slide it along the wires until you can see underneath it. Using the spray cement, shoot a short burst into the cavity on each side as well as the bottom. Push the foil back down into the cavity with your fingers and press it into the glue. Do this for both pickups.
Turn the guitar upside down. Press foil down into the back cavity. Cut out holes for any parts that have wires going to them. Mold the foil around the parts. Press the foil down around them, and don't worry if the foil has gaps in it. Try to cover as much of the wood with foil as you can. Lift the foil up slightly and spray some glue under it. Press it back down to finish. Trim off the excess foil with scissors. Screw the cover back on.
Screw the pickups, the retainer rings and pickup guards back on. Put on a fresh set of strings.
Check your guitar cord. If it is frayed or loose it can also lead to guitar buzz or hum.
Don't let any bare wires or bare contacts touch the foil. Don't spray glue into any controls.