that not MMA (stick) welding, you are talkng about bracing. mma can be done either in AC or DC, unlike any other than TIG for ali. you can reverse the path of the current, i.e the arc going for the earth'd job to the stick or the stick going to the earth, this change is quite substantional. it is essectially a metalic rod covered with a flux, meaning no need for an inert gas to form a shroud. this is why all outdoor welding is MMA : ship building building erection etc. rule of thumb is the size of the rod will produce a weld throat joint 1 mm larger than it, thus a 4.0mm rod will produce a miniu, of a 5mm weld etc unlike MIG and TIG the positioning of the earth is critical, the quality of the eletrical earthign is effected by the distande the earth is away from the job, uhnlike MIG and TIG you are left with bi product, namely slag, which has to be chipped off, although the sign of a good weld is the slag should be curling off aprox 10mm behind the elctrode ask anything else, i build pressure tested vessles for oil rigs etc