Copper smelting during the Edo Period
The Sumitomo copper business began in 1590 in Kyoto. Copper smelting and decorative copperwork were performed under the name Izumiya. Copper ore from all parts of Japan was turned into refined copper metal. Sumitomo was the first in Japan to perfect a smelting technique known as "Nanban-buki" for the separation of copper from silver. Prior to the development of this technology, copper was exported with high levels of silver impurities, which sharply reduced potential smelting profits. The competitive advantage gained from this more advanced technology helped Sumitomo to establish a highly profitable base of operations.
In 1690, large outcrops of copper ore were found on the southern slopes of the Akaishi Mountain range in Ehime Prefecture. The Besshi copper mine that was developed at that location went on to operate continuously for 283 years and substantially underpinned Sumitomo's development. Once the first shaft was dug at Besshi, the Sumitomo family firm shifted focus from just smelting copper to become a full-fledged industrial resource business.
Operations at Besshi did not always proceed smoothly. Within eight years of the first shaft being dug, annual copper production had risen to 1,521t. Output then dipped, however. As the tunnels became deeper, operations were troubled by the discharge of water which built up in the mine. The transportation over long distances of the wood and charcoal required for smelting also drove up production costs. Employing methods to drain away the water together with the periodic use of forestry helped to stabilize operations.