Raudanvalmistus

Raudanvalmistus refers to the historical and traditional process of iron production, particularly in Finland and its neighboring regions. This method involved smelting iron ore in a bloomery furnace, a relatively simple type of furnace used in pre-industrial times. The primary goal of raudanvalmistus was to extract metallic iron from iron-rich materials like bog iron ore or lake ore.

The process typically began with the collection of raw materials. Iron ore, often found in bogs and lakebeds, was gathered. Charcoal, produced from the burning of wood in the absence of air, served as the fuel and reducing agent. These materials were then loaded into a bloomery furnace, which was usually constructed from clay or stone.

Once the furnace was filled, it was heated to high temperatures, typically using bellows to supply air and intensify the combustion. The heat and the carbon from the charcoal caused a chemical reaction, reducing the iron oxides in the ore to metallic iron. However, the temperatures in a bloomery were not high enough to melt the iron completely. Instead, the iron formed a spongy, porous mass known as a bloom, which was interspersed with slag, a glassy byproduct of the smelting process.

After smelting, the bloom was removed from the furnace and repeatedly hammered and heated to consolidate the iron and expel the slag. This process, known as forging, was crucial for refining the iron and making it more workable. The resulting wrought iron was then ready for use in crafting tools, weapons, and other necessary items. Raudanvalmistus was a labor-intensive and often inefficient process, but it was the primary method of iron production for centuries before the advent of more advanced industrial techniques.