Furnace

The Furnace is a core production building used to smelt ores and make Glass. It is one of the most important industrial facilities in the game, since many construction chains and advanced recipes require metal ingots in large quantities.

A Furnace can produce Copper Ingot, Gold Ingot, and Iron Ingot from the corresponding ore, along with Charcoal or Coal and, for iron, either Lime Powder or Bone Powder depending on the recipe. It can also smelt Sand into Glass. The work cost differs by recipe: standard 1-ore recipes take 800 to 1000 work, while the larger 2-ore recipes take 900 to 1600 work, with Glass also scaling up from 600 work for the smaller batch to 900 work for the larger one.

Because ingots and Glass are demanded everywhere, it is common to build many Furnaces over the course of a colony’s development, often around 8 to 10 in the late game. More can be justified if you are turning large amounts of Copper Ingot into Coin through the Mint. The building is also well suited to Ratron labor, making it easy to assign workers to smelting duties.