I decided to try to dc tig weld on the surface of 1/4" aluminum plate. I used 100% argon and around 250 amps with thoriated tungsten. it was a lot different than ac tig with pure tungsten,but at the same amperage. i brushed off the weld, and showed it to someone. they said, "Did i stick rod it." It is a lot cleaner than stickrod,but with the same shiny weld. The bead appearance was shaped more like stickrod than ac tig. it looks strange when attempting it,however it could help if i have to try welding thick aluminum plate 1" thick again. i prrobably would do atleast my first pass in dc tig to insure good penatration. tthen cover it with the more traditional ac tig bead on top!