A MIG welder (Metal - Inert Gas) passes a current through a continuously fed solid core wire which strikes an arc against the substrate. The wire feed gun head floods the wire end with an inert gas such as Argon to shield the weld area. The arc melts the wire and heats the substrate forming a welding puddle which the welder advances to build a finished weld. Arc/Stick welding uses a fixed rod which is coated in a solid flux to strike an arc with the substrate. The heat of the arc melts the flux agent which floats on the top of the weld puddle shielding it from oxygen. The welder advances the stick and puddle to build the finished weld. Oxy Acetylene welding uses a neutral flame formed by combusting Acetylene gas wth Oxygen. A flame of about 6000degF is formed. The heat of the flame melts the substrate and forms a puddle which fills the weld gap forming a finished weld. A welder can add a filler rod if needed to improve weld quality. A plasma cutter forms an arc in a nozzle which heats a high speed pressurized stream of inert gas, often Nitrogen or Argon, ( occasionally non-inert Oxygen) which impinges on a workpiece. The imense heat of the plasma (15,000 degC typical) melts and oxidizes the substrate and blows the debris clear of the work.