The trickiest part of vertical up welding, be it MIG or stick, is getting the edges of the weld to "wet" properly on the sides. To little, and the weld will end up being humped in the middle, and it won't be strong b/c it lacks fusion on the sides. Too much, and you get undercut, which traps slag (with stick or flux-core welds) and is a weak spot. With a subsequent "hot pass" after your first, you may be able to completely nullify the effects undercut will have on the weld, but not always. Sometimes you need to grind it. What I have a tendency to do if I have welded V-up in awhile is not point weld far enough to the left and right as I weave, and not hold the weld to the sides long enough to prevent undercut. This only leads to me not whipping the weld back across the middle fast enough, causnig it to hump, or in the worst case, drip.:Banghead As was said before, proper amps, wirefeed for MIG, and electrode size for stick. Another key is being able to build and hold your "shelf" as you progress up the part. Your shelf helps keep the weld where it needs to be, and without that, you ain't gonna have any luck. Bear in mind, the larger diameter the elcetrode, the harder it is to weld verticle up b/c of the heat needed to make it weld properly. If you can't do it with 1/8" rod, try 3/32". When I had to take my cert. tests in school, all of the stick was verticle up, 1/8" dia. rod. 5//32" is doable if the plate is heavy enough, but I've never tried larger for verticle up. Hope I helped some.
