A bloomer furnace is a type of furnace used in the production of iron. It is a simple, early design that combines iron ore, charcoal, and limestone to create molten iron. The furnace is typically built in a vertical structure, allowing for the materials to be layered and heated over time. The bloomer furnace operates at lower temperatures compared to modern furnaces, resulting in a product known as bloom iron. This iron is not fully melted but is instead a spongy mass of iron and slag, which can be further processed into usable metal products.