One way to tell Al filler wires apart is drop the wire onto a hard surface and listen to the ring it has when it bounces. 4043 has a "dead" ring to it, 5356 has a "clear" tone that rings out even in a noisy-ish shop... Its hard to describe but give it a try with fillers that you...

While cleaning up shop here I came across some old filler rod. It appears to aluminum, It was in a cardboard tube with Union Carbide markings (might be unrelated), and the rod is stamped '35S'. It's 1/8" diameter. I'm curious about it, anyone recognize the stamp number? Nothing compelling came ...

Are you welding steel that has a galvanizing or another type of coating? It kinda looks like something has boiled off and jumped up onto your Tungsten. Galvanized steel will do this.

Pete

I built this one when I was practicing 'T' joints. Made setting up easy.