The influence of shielding gas composition on arc properties including temperature, voltage, heat flux and shear stress at the anode and also the weld depth as indicated by the maximum temperature of a water cooled anode is investigated. It is found that the additions of helium, hydrogen and nitrogen to argon all increase the arc and anode temperature. For helium, this is due to the lower electrical conductivity; in the other cases, it is due to the higher specific heat.