<P> In Europe a similar liquid process in open - topped crucibles took place which was probably less efficient than the Roman process and the use of the term tutty by Albertus Magnus in the 13th century suggests influence from Islamic technology . The 12th century German monk Theophilus described how preheated crucibles were one sixth filled with powdered calamine and charcoal then topped up with copper and charcoal before being melted, stirred then filled again . The final product was cast, then again melted with calamine . It has been suggested that this second melting may have taken place at a lower temperature to allow more zinc to be absorbed . Albertus Magnus noted that the "power" of both calamine and tutty could evaporate and described how the addition of powdered glass could create a film to bind it to the metal . German brass making crucibles are known from Dortmund dating to the 10th century AD and from Soest and Schwerte in Westphalia dating to around the 13th century confirm Theophilus' account, as they are open - topped, although ceramic discs from Soest may have served as loose lids which may have been used to reduce zinc evaporation, and have slag on the interior resulting from a liquid process . </P> <P> Some of the most famous objects in African art are the lost wax castings of West Africa, mostly from what is now Nigeria, produced first by the Kingdom of Ife and then the Benin Empire . Though normally described as "bronzes", the Benin Bronzes, now mostly in the British Museum and other Western collections, and the large portrait heads such as the Bronze Head from Ife of "heavily leaded zinc - brass" and the Bronze Head of Queen Idia, both also British Museum, are better described as brass, though of variable compositions . Work in brass or bronze continued to be important in Benin art and other West African traditions such as Akan goldweights, where the metal was regarded as a more valuable material than in Europe . </P> <P> The Renaissance saw important changes to both the theory and practice of brassmaking in Europe . By the 15th century there is evidence for the renewed use of lidded cementation crucibles at Zwickau in Germany . These large crucibles were capable of producing c. 20 kg of brass . There are traces of slag and pieces of metal on the interior . Their irregular composition suggests that this was a lower temperature, not entirely liquid, process . The crucible lids had small holes which were blocked with clay plugs near the end of the process presumably to maximise zinc absorption in the final stages . Triangular crucibles were then used to melt the brass for casting . </P> <P> 16th - century technical writers such as Biringuccio, Ercker and Agricola described a variety of cementation brass making techniques and came closer to understanding the true nature of the process noting that copper became heavier as it changed to brass and that it became more golden as additional calamine was added . Zinc metal was also becoming more commonplace . By 1513 metallic zinc ingots from India and China were arriving in London and pellets of zinc condensed in furnace flues at the Rammelsberg in Germany were exploited for cementation brass making from around 1550 . </P>

Which metal is present in brass bronze and german silver