Copper smelting

Casting bronze ding-tripods, from the Chinese Tiangong Kaiwu, published in 1637.

Smelting is the process of applying heat to ore in order to extract a base metal. In the case of copper, combining tin, lead and/or arsenic in the right proportions produces bronze, an alloy that is significantly harder than copper.

Process

Smelting is usually done using a furnace, whose design can be as simple as a pit in the ground. In this case, with copper ore and bellows, one of the possible processes steps are the following:

1. Dig a small pit unto the ground using an antler pick or another tool, such as a stick.
2. Cut a small groove into the edge to allow air from a set of leather bag bellows.
3. Crush the copper ore on a small anvil until it is a fine powder.
4. Light a fire in the pit and add charcoal.
5. Sprinkle the crushed ore onto the hot coals. Add more charcoal.
6. Place the end of the bag bellows in the pit, as well as a turf cap over the pit.
7. Force air into the pit by the bellows, increasing the temperature inside and creating a simple furnace. Continue for a couple of hours.
8. Changes in the color of the flame coming out of the pit show the progress of the smelting. When the process is complete, remove the cap and retrieve the metal.
9. Wash the remains in the pit to check for smaller fragments of copper metal by panning.
10. Collect the fragments, put them into a ceramic crucible and return them to the furnace to be melted together.

The metal is has a pinky yellow color. Small amounts of tin or lead can be added to produce the stronger bronze alloy. The chemical reaction is what changes the ore into metal, rather than the temperature in the furnace: the carbon monoxide produced by the burning charcoal bonds with the carbon in the ore, producing carbon dioxide and copper metal in the process.

Normally, a natural draft furnace using wood, a kiln, can reach up to 1400 Celsius degrees (or 2552 Fahrenheit), while a furnace that uses fuel such as charcoal can reach temperatures up to 1600 °C (2912 °F) degrees.

See also

• Bloomery Furnace
• Oxygen

External links

• Prehistoric copper smelting in a pit!, ancient1580, 25 May 2012, YouTube

Further reading

• Rehder, J.E. (2006). The Mastery and Uses of Fire in Antiquity. McGill-Queen's University Press. ISBN 0773530746.
• DA Chapman RCA, SG Chapman MA AIFA (2013). Reconstructing and testing the Pentrwyn pit furnaces, ancient-arts.org. Archived on 6 November 2020 from the original link.

This article uses material from the Wikipedia article Smelting, which is released under the Creative Commons Attribution-ShareAlike 3.0 Unported License (view authors).