Found Dreaming

A good "Tell" with regard to proper metal casting temperature, is witnessing a narrow ring of bubbling silicon from the crucible's inside edge to the melt. I keep watching it a while longer till I see a hint of the metal volume "quivering" like it's being vibrated slightly. That's when you know the melt is actually "boiling"... or I prefer to call "simmering"! I witness the "hint" of quivering, shut down the furnace, skim and flux without a lot of rush to get it done (giving the metal time to settle down and stop boiling/simmering), and then remove from the furnace and pour. Pouring too hot never produces a good cast.

Thanks Frank, I hope to get to try this again soon. It had no vents because I was going to use my vacuum table to drawn the metal in but the investment started falling apart and wanted to slide out of the metal flask. The whole thing went south fast.

I use ludo which probably accomplishes a similar thing as grog---maybe. It works for me. I use the small mesh chicken wire too. Without it the molds tend to crack and fall apart.

I have found that if I pour at 47 millivolts on my pyrometer, which is a bit over 2000 F., I get a good smooth surface with no black stuff. Any higher and the surface is not as good. Plaster investments do not like higher temperatures.

Richard