Electric Soldering Iron: Miner, 1890

Earlier electric soldering irons heated a hollow copper head from inside, through finely divided carbon pressed against the tip, so the whole outside of the head lost heat to the air. Willard M. Miner of Plainfield, New Jersey, patented the alternative in 1890, US 421,185: keep the copper head solid, which holds its heat longer, and wind the heating resistance round the outside of it, under a shell that concentrates the heat on the copper and stops it escaping. The coil is German silver wire, wound round a reduced part of the head without touching it, with one end connected to the head and the other to the supply.