Thank you gnabgib and ogorir; It was the helmet sensitivity. I thought it might have been a contaminant causing the arc to flare, but it was simply the helmet (and my newbness). I had never considered that the arcs for different materials could have different intensities, and I had the helmet set up...

I'm a newb but I've done a couple of projects, like a full aluminium 'cage' roof rack for my 4WD. Whenever I weld mild steel the arc is so bright when I start that I get a patch in the middle of my vision which is hard to see through (which makes it difficult to judge the arc position/length after t...