This page links to a film on Youtube. Alternate material is provided for readers in China, where Youtube is not accessible.
Christopher D. Roy, ‘From iron ore to iron hoe: Smelting iron in Africa’ (从铁矿到铁锄•非洲炼铁技术), 1 hour 45 minutes. https://www.youtube.com/watch?v=RuCnZClWwpQ.
This version has Chinese subtitles.