I thought I'd throw this out there. I'm welding 3" .065 wall stainless with 1/16" tungsten & a #8 cup.
After getting my settings and process down I needed to have my argon cylinders replaced. After I hooked them up I began work again and found my weld inside was dark in color, almost like there was oxygen in the gas. Of course I didn't think they could have given me bad gas because it was just argon, not a mix. After trying a number of settings and process changes I came to the conclusion that the only thing that changed was the new cylinders of argon. I called to have them replaced and all the sudden my shiny silver inside weld reappeared (they thought I was crazy when I called them and said "I got bad gas!"). Apparently when they filled them they didn't get the proper vacuum on it. Wow! what a lesson for me that the gas suppliers can give you bad gas.
