So I've been using the wrong flux for aluminum for like two years
Honestly, I felt like a total goof. We had this big job in Toledo, a custom run of about 500 decorative castings, and the metal just kept coming out grainy and full of pits. My crew and I were chasing our tails for a week, checking temps and mold prep. The tip off was when our new guy, fresh from trade school, quietly asked if we were using a sodium-based flux. I said yeah, the big green tub we always get. He just nodded and said his teacher swore by a chloride-based one for aluminum, that the sodium stuff was more for iron. I looked at the tub label and sure enough, it said 'For ferrous metals' right on the side. I'd been grabbing it off the same shelf for so long I never read it. We switched and the next pour was smooth as glass. Has anyone else had a 'duh' moment with a basic material like that?