The process of making tin through a refining process known as cupellation can be traced back at least 4,000 years. Tin smelting developed independently in both Europe and the Far East. The earliest known tin production is believed to have happened in todays English Midlands around 2500 BC. Since then, tin has been an essential part of life, from the very beginning of widespread metalworking.
In the Far East, tin was known to have been used as early as 1500 BC. As the Chinese developed their tin currency, the peak of tin production occurred during the Tang Dynasty (AD 618–906). The Japanese were also users of tin, and it is thought that their tin mining decreased around 1000 when their own cupellation processes were developed.
Cupellation, also known as cuperation, is the process of melting, smelting and refining metal by heating it in a cupel, or closed crucible. A cupel is made from bone or clay ash and is used to hold the metal in place while smelting. It provides a porous surface that allows air and volatile substances in the form of fumes and smoke to escape. The heat from the fire is then absorbed by the crucible, helping to speed up the process of separating the metal from any attached impurities.
The cupel is not only responsible for keeping the metal contained during the smelting process, it also affects the purity of the finished product. As the metal is processed, certain elements are left behind in the cupel as oxides, while others are evaporated. The refinement process is also enhanced when the cupel is lined with charcoal, which acts as a filter to absorb and trap impurities.
The process of cupellation was brought to Europe by the Phoenicians sometime around 1000 BC. It is believed to have spread far and wide, reaching the Anglo-Saxons, Scandinavians and the Celts. As the popularity of tin smelting grew, the techniques used for refining the metal were further improved upon. By the eighteenth century, the English were the leaders in tin production, with their refined processes allowing for more rapid production of higher-quality tin.
Today, tin is still an important metal in many industries, from engineering construction to electronics. It is often found in solders, alloys and numerous other products due to its excellent corrosion-resistant properties. Although modern technology has changed the process of smelting tin, the technique of cupellation is still widely used. The cupel technique is perhaps the oldest method of refining metals, and its principle remains unchanged despite centuries of development and improvement.
