I saw it in a tutorial on Internet and if I run the code it work(I don't know how it works) : I have the copper block and the copper ingot, but when i put the copper ore in the furnace, it didn't work. I try to change the code to GameRegistry.addSmelting(ItemInit.COPPER_INGOT, new ItemStack(ItemInit.COPPER_INGOT), 0.2f); and it work because if I smelt a copper ingot it makes a Copper Ingot, I try to change also with Blocks.DIRT and it work but with BlockInit.ORE_COPPER_ORE it doesn't work