Tinning electrical wires can turn stranded wires into solid wires. Soldering wire strands, often called tinning, is the way the professionals ensure that wires strands don't fray and separate when the terminal is tightened down on the wire. By using a soldering iron to add rosin-core solder to the wire strands, the solder fills in the voids between the wire stands and causes the loose, fine wires to become one solid wire that can be easily bent and placed underneath the terminal screws. This ensures a tight connection and virtually eliminates the possibility of loose strands touching the junction box or coming out from beneath the terminal screw.
Soldering should be performed with caution! Th soldering iron gets very hot and can cause severe burns. Always place soldering iron on a heat-resistant surface while it heats up and cools off. Wile soldering, be sure to work over a heat-resistant surface and away from anything flammable. Only rosin-core solder should be used. It has been called the electrical solder because it is acid free, unlike acid-core solder that will corrode the wire strands.
So the next time you have to work on stranded wires, like those in a lamp cord, remember this simple, little quick tip, simple get out your soldering iron, some rosin-core solder, and let the tinning begin.