A permanent magnet is a piece of metal that holds onto magnetic properties outside the presence of an external magnetic field. Describing them as permanent is not quite accurate, however. Although "permanent" magnets are able to retain their magnetic properties, on their own, for long periods of time, these magnetic properties are subject to being weakened or even neutralized under certain conditions. For example, a permanent magnet is neutralized when heated to a temperature above the Curie point (see Resources) for that particular metal. To restore a permanent magnet, you need to cool the metal (if heated) and expose it to a magnetic field.
Coil your copper wire tightly around the piece of metal you would like to restore as a permanent magnet. This coiling process produces what is known as a solenoid. A solenoid is a spiral of wire that produces a magnetic field when an electric current is passed through it. With every individual coil you make, you increase the strength of the magnetic field the solenoid is capable of generating. Leave at least six inches of wire free at the ends of the coils.
Connect the ends of the copper wire to the terminals on your power supply.
Turn on the power supply and activate the current. This creates a magnetic field.
Wait ten seconds; then turn off the current.
Test to see if your permanent magnet has been restored. Place a nail or a paper clip near the metal to see if it will attract it. If your permanent magnet hasn’t been restored, it may mean you need to generate a stronger magnetic field. Go back to step one, and coil more wire around the metal.
A somewhat weak permanent magnet can be produced using the stroking technique. Stroke the metal you would like to restore as a permanent magnet with another permanent magnet. Press down hard on the magnet to be restored with an alternate permanent magnet. Stroke the permanent magnet across the magnet you’re restoring. Each stroke needs to go in the same direction. DO NOT make a back and forth motion with your strokes. When your permanent magnet comes to the end of the metal you’re restoring, lift up the permanent magnet and place it back at the other end of the magnet to be restored and stroke it again. Keep repeating this stroking procedure until the magnet you’re restoring has been re-magnetized.