reproduction of yunzi. The Yunnan Sports Commission investigated the Yunzi manufacturing processes and rediscovered the art by reverse engineering a few original Yunzi. In 1974, the state-run Yunnan Weiqi Factory began manufacturing yunzi stones. They are used in professional weiqi tournaments in China and elsewhere. According to Chinese law, the yunzi stones can only be produced by the state run Yunzi company. The company creates the yunzi in an old factory that was used by the American Flying Tigers as barracks during World War II. The formula is thought to be ground Yunnan mountain stones and agate. Caring for yunzi Like other types of Go stones, yunzi are washed and dried using a gentle soap solution to remove any dust from the packaging/manufacturing process. Although a light coat of oil, wiped clean, will help yunzi stones appear at their best, care must be taken in oiling yunzi. Because vegetable oils, such as olive or canola oil, will oxidise and become rancid over time, they should not be applied to yunzi to avoid developing an unpleasant odor. Instead, common practice is to use an unscented mineral oil to oil yunzi; alternatively, stones may be washed but remain unoiled; over time, the natural oils incurred by human touch will polish yunzi to a sheen. Like glass Go stones, yunzi are very durable. However, like glass stones, yunzi are still at risk for chipping if they are dropped or otherwise come into sharp contact with hard surfaces such as metal, tile, or stone. See also Go equipment References External links A Blogger's photos from the Yunnan Weiqi Factory Yunnan Weiqi Factory english page History of Go Go equipment Culture in Yunnan