Tig welding help????????????

[wareagle]

A question on tig welding aluminum.....using 3/32 green tungston with 3/32 4043 filler ,,,,welding .125 ga al......i'm am alright after i get the material tacked togather.i am just practicing making cubes. I seem to have problems getting the material tacked togather. I try to let the aluminum get shinny,ready to accept the filler and sometime everything goes well,and sometimes the ouside corner mostly acts like it has became containmaneted or something....looks like ****...the outside corners are the worst about this..i have all the setting in auto using pure argon flow set at about 15 i tried lowering amps,raising amps,,,,,,,,like i said sometimes it works fine,sometimes not..and when you try to weld over these ****ty tacks,most of the time is looks no good...if i can get this part straighten out,then i will feel 100% better,,,,,,,,,,any help on putting tacks on outside corners on aluminum now once i get rolling it looks sweet....i have a lincoln 275 preision tig if this helps,built in pulse,with the advance control panel.........please help on outside corners tacking????????????????????aluminum thanks