The smelter also requires free space on the LEFT to be filled with ore and on the RIGHT to be filled with Coal. The Smelter uses approximately 1 Coal every 15 seconds as fuel. It takes 31 seconds to produce one bar of Metal. It can hold a total of 20 coal and 10 ores. ... Immune to. Ore TypeIron Time (sec.)30 Ores1 Coal3 3 more columns