The Swansea Vale Spelter Company was established at Llansamlet, near Swansea, in about 1873. Despite a major fire in 1913, by 1921 the works was the largest in the country.
During the First World War, the National Smelting Company was formed, with the co-operation of the British Government, in order to increase the production of spelter (zinc) as the UK was dependent on imports for three-quarters of its supplies. Spelter is an alloy of equal parts of copper and zinc (i.e. a brass) and sometimes also contains lead. The company operated a production site at Avonmouth and in 1923 took over the Llansamlet works of the Swansea Vale Company. By 1927 The Swansea Vale Works was the most important plant in the industry, and was to become the largest of its kind in the United Kingdom. In 1929 the Imperial Smelting Corporation took over from the existing company.
Source: Grace's Guide.
B.A.Malaws, RCAHMW, 24 October 2013.