Enamel: Portrait miniatures painted on enamel in oil with copper support was a method created in Italy during the 16th century. There is debate as to whether this method was attributed to Italian artists or Dutch artists. During the 17th, 18th, and 19th centuries, portrait miniature artist used enamel with a copper support in Germany, Portugal, and Spain. Many Dutch and German artists adopted copper as a medium further enhancing the images. Over time, only elite could afford the copper forcing artists to stretched vellum, ivory, or paper. Dutch and German miniatures were painted in oil, and as a rule these are on copper; and there are portraits in the same medium, and often on the same material, attributed to many of the great Italian artists, notably those of the Bologna school. Samuel Cooper is said to have executed a few paintings in oil on copper. Beginning in the mid-17th century, many watercolors were conducted with vitreous enamel. Jean Petitot 1607–1691 was the greatest worker in this material, and painted his finest portraits in Paris for Louis XIV of France. His son succeeded him in the same profession. Other artists in enamel were Christian Friedrich Zincke (died 1767) and Johann Melchior Dinglinger. Many of these artists were either Frenchmen or Swiss, but most of them visited England and worked there for a while. The greatest English enamel portrait painter was Henry Bone (1755–1839). A great collection of his small enamel reproductions of celebrated paintings is in the British Royal Collection.Enamel stayed a consistent and robust alternative to portrait art miniatures during the 18th and 19th centuries.