A Bar of Copper is received when successfully Smelting Copper Ore in an Ore Smelter. A Bar of Copper can be stored in a Stockbin.
The amount Ore Metal Bars produced in your Ore Smelter is based partially on chance but mostly influenced by the Ore/Lime ratio and your Alloying Artifact Bonus. Currently, the best Ore/Lime ratio is 13x Lime and 12x Any Ore of one type. To smelt place your Lime and Ore in a lit Ore Smelter. After about 40 minutes 1x, or rarely 2x, of your Ores will be replaced with a corresponding Ore Metal Bar and the rest of your Ore will have become Dross. Each time a Dross is produced there is a chance for it become A Face in the Dross instead. A using Little Limestone in place of one of your Limes will also increase the number of Metal Bars that are created.