This portrait is painted in enamel on metal. The advantage of enamel over traditional miniature painting (watercolour painted on vellum or, from about 1700, on ivory) is that it does not fade when exposed to light. The process of painting with enamels is, however, less free than the miniature technique and is fraught with danger. The first colours to be laid on the metal support have to be those needing the highest temperature when firing. More colour is added and the enamel refired, the process ending with the colours needing the lowest temperature. Such labour meant that it was an expensive option.

Enamel was first practised in England in the 1630s by the Swiss goldsmith Jean Petitot at the court of Charles I. It was reintroduced around 1680 by a Swede, Charles Boit, and achieved wide popularity with the work of Christian Friedrich Zincke of Germany. Both Boit and Zincke were goldsmiths by training and painted only enamels rather than traditional portrait miniatures in watercolour on vellum or ivory. This is a typical example of Zincke’s hugely fashionable work. Charles, 2nd Duke of Grafton (1683-1757) was a British courtier and politician who held the post of lord chamberlain, and was a close friend of George II.