The steel industry dates back to at least the 14th century. In 1740 Benjamin Huntsman discovered the crucible technique for steel manufacture, at his workshop in the district of Handsworth. This process had an enormous impact on the quantity and quality of steel production and was only made obsolete, a century later, in 1856 by Henry Bessemer's invention of the Bessemer converter which allowed the true mass production of steel. Bessemer had moved his Bessemer Steel Company to Sheffield to be at the heart of the industry. Thomas Boulsover invented Sheffield Plate (silver-plated copper), in the early 18th century. A major Sheffield steel invention was that of stainless steel by Harry Brearley in 1912, and the work of Profs. F. B. Pickering and T. Gladman throughout the 1960s, '70s, and '80s was fundamental to the development of modern high strength low alloy steels.