Vitreous enamel, the kind of enamel used on metal, is a substance of powdered glass fired on metal. The art of enameling dates back to the ancient Egyptians who applied enamels to pottery, stone, decorative items, household items, and jewelry. The ancient Greeks, Chinese, Celts and Georgians also practiced the art of enameling. Vitreous enamel can be applied to most metals; stainless steel, copper, cast iron, gold, silver and aluminum can be used as substrates. Enamel's desired properties, such as smoothness, hardness, durability, high scratch resistance, and resistance to fading makes it ideal for large industrial uses, from cooking items to large storage structures. Cloisonné, where colorful enamel is separated by thin steel, is still produced today, mainly in China.
Abstract art is non-representational art or sculpture that does not depict elements of the natural world and signify a departure from realistic portrayal. Art from the Renaissance to the 19th century was realist and representational in nature. As European artists began to be exposed to art from other cultures, they found new ways to depict visual language. By the late 19th century, abstract forms and works began to appear in the art world.