their line of soldering irons. In 1905, Scientific American Magazine, published a tutorial on making a soldering iron that clearly explains how early irons were made. In 1921, a German company founded by Ernst Sachs developed an electrical soldering iron similar to American Electrical Heater Company iron. Types Simple iron For electrical and electronics work, a low-power iron, a power rating between 15 and 35 watts, is used. Higher ratings are available, but do not run at higher temperature; instead there is more heat available for making soldered connections to things with large thermal capacity, for example, a metal chassis. Some irons are temperature-controlled, running at a fixed temperature in the same way as a soldering station, with higher power available for joints with large heat capacity. Simple irons run at an uncontrolled temperature determined by thermal equilibrium; when heating something large their temperature drops. A variation is the Scope soldering iron, common in Australia, which operates from a low-voltage source such as transformer or battery, and heats in seconds when the user pushes the thumb-guard, which then acts as a heat controller. Cordless iron Small irons heated by a battery, or by combustion of a gas such as butane in a small self-contained tank, can be used when electricity is unavailable or cordless operation is required. The operating temperature of these irons is not regulated directly; gas irons may change power by adjusting gas flow. Gas-powered irons may have interchangeable tips including different size soldering tips, hot knife for cutting plastics, miniature blow-torch with a hot flame, and small hot air blower for such applications as shrinking heat shrink tubing. Temperature-controlled soldering iron Simple soldering irons reach a temperature determined by thermal equilibrium, dependent upon power input and cooling by the environment and the materials it comes into contact with. The iron temperature will drop when in contact with a large mass of metal such as a chassis; a small iron will lose too much temperature to solder a large connection. More advanced irons for use in electronics have a mechanism with a temperature sensor and method of temperature control to keep the tip temperature steady; more power is available if a connection is large. Temperature-controlled irons may be free-standing, or may comprise a head with heating element and tip, controlled by a base called a soldering station, with control circuitry and temperature adjustment and sometimes display. A variety