of Shah Jahan in the mid-17th century. Transparent enamels were popular during this time. Both cloissoné and champlevé were produced in Mughal, with champlevé used for the finest pieces. Modern industrial production began in Calcutta in 1921, with the Bengal Enamel Works Limited. Enamel was used in Iran for colouring and ornamenting the surface of metals by fusing over it brilliant colours that are decorated in an intricate design called Meenakari. The French traveller Jean Chardin, who toured Iran during the Safavid period, made a reference to an enamel work of Isfahan, which comprised a pattern of birds and animals on a floral background in light blue, green, yellow and red. Gold has been used traditionally for Meenakari jewellery as it holds the enamel better, lasts longer and its lustre brings out the colours of the enamels. Silver, a later introduction, is used for artifacts like boxes, bowls, spoons, and art pieces. Copper began to be used for handicraft products after the Gold Control Act, was enforced in India which compelled the Meenakars to look for an alternative material. Initially, the work of Meenakari often went unnoticed as this art was traditionally used on the back of pieces of kundan or gem-studded jewellery, allowing pieces to be reversible. Modern More recently, the bright, jewel-like colours have made enamel a favoured choice for jewellery designers, including the Art Nouveau jewellers, for designers of bibelots such as the eggs of Peter Carl Fabergé and the enameled copper boxes of the Battersea enamellers, and for artists such as George Stubbs and other painters of portrait miniatures. A resurgence in enamel-based art took place near the end of the 20th century in the Soviet Union, led by artists like Alexei Maximov and Leonid Efros. In Australia, abstract artist Bernard Hesling brought the style into prominence with his variously sized steel plates. Enamel was first applied commercially to sheet iron and steel in Austria and Germany in about 1850. Industrialization increased as the purity of raw materials increased and costs decreased. The wet application process started with the discovery of the use of clay to suspend frit in water. Developments that followed during the 20th century include enamelling-grade steel, cleaned-only surface preparation, automation, and ongoing improvements in efficiency, performance, and quality. Properties Vitreous enamel can be applied to most metals. Most modern industrial enamel is applied to steel in which the carbon content is controlled