Pouring Temperature: Too Cold Misruns, Too Hot Tears the Mould

Metal is not poured at its melting point. It is poured at a SUPERHEAT above it — enough that it can travel through the gating and fill the last thin corner before it starts to freeze. Too little superheat and the metal stops before the cavity is full, or two streams meet and fail to fuse. Too much and it dissolves more gas, oxidises harder, burns the sand, and shrinks more on the way down — so the porosity gets worse rather than better. The window is perhaps 100 to 150 degrees wide, it differs by alloy and by casting, and the only way to sit inside it reliably is to MEASURE. Judging melt temperature by colour is the pyrometer rung's warning delivered with molten metal.