A Bar of Pig Iron is received when successfully Smelting Iron Ore in an Ore Smelter. In addition to crafting, a Bar of Pig Iron can also be purchased from Torvold Starkajärn in Providence for 200x Silver Pieces. A Bar of Pig Iron can be stored in a Stockbin.
The Purity of a Bar of Pig Iron comes from the Iron Ore Boulder the Iron Ore used to make it, was Chipped from. Iron Ore Boulders' get their Purity from a combination of Mine Level, distance from the ramp, and chance. Iron Purity will transfer directly onto Fish Hooks, Knife Blades, or any Wrought Iron Bars made from it.
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. Using a Little Limestone in place of one of your Limes may also increase the number of Metal Bars that are created.