This document describes the results of a series of tests to determine the advantage of a square wave A.C. power source over D.C. for controlling arc blow. Initial assessments of both arc extinction and arc blow characteristics for D.C. and A.C. power sources were conducted. with E6010 and E7018 electrodes. Arc blow effects were assessed by comparing bead displacement and regularity for different current types. The experiments demonstrated that the square wave A.C. power source had significant advantages over D.C. for controlling arc blow.