Brass and tin bronze remained for centuries the principal copper alloys and it was not until the rapid development of metallurgy in the 19th Century that other and now familiar alloys began to be used. Brass long continued to be made from copper and calamine. Its production was not easy, particularly as the copper itself was not very pure; and small impurities in the pure metal and the alloy can have detrimental effects on both metals. It was only in 1738 that a patent was taken out by William Champion to distil metallic zinc (or spelter) from calamine, by reduction with charcoal or stone coal. The works at Bristol then began to produce a brass of high quality at the rate of 200 tons per annum. At that period both brass and copper were cast into billets and cakes in stone moulds and a particular virtue was attached to stone from St. Malo for that purpose.
Meanwhile the use of rolling mills was beginning to supplant the old battery mills for many products; but it was not until the mid 19th Century that really powerful rolling mills were installed, although the Dockwra mill at Swansea had been working since 1697.