Brown oxide

[christian]

Yeah,

What's your argon tank size, in CF?

When my tanks (200 CF) get down to about 200 psi, the shielding seems to get compromised.

You may be long-arcing a bit too.

I'd give yourself a little longer stick-out on the tungsten, so you can see the tip better to keep a tighter arc. Your cup size, your CFH setting, and the gas lens should all support that well enough.

Maybe get one of those cheap torch flow meters, to confirm that your gas lens isn't constricting the flow somehow.