Electrum Smelting
Again, exactly like this (3 gold, 3 silver), but can use charcoal instead of coal; takes 4 seconds
Steel Smelting
This exact configuration is required (5 iron); takes 5 seconds Note: In v1.3 and later, this is no longer the recipe. It now requires a coal in the 6th slot, and can use either coal or charcoal in the bottom slot
Invar Smelting
No changes (4 iron, 2 nickel) except coal or charcoal; takes 4 seconds