there are two basic types of enamel used on magnet wire, the regular enamel, which carbonizes when you heat it, and makes an oxide layer on the wire that won't take solder, and another enamel that goes by trade names like "thermo-strip", which when heated to soldering temperatures, peels off of the copper wire, leaving bare copper. when making coils in a factory, the wire ends are dipped in a solder pot which strips the enamel off and tins the wire in one quick easy step.