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. In the early 18th century a number of miniaturists took up enamel in order to offer their clients a choice. It is not known who the painter of this enamel was, but it is probable that this is a copy after an oil painting rather than an original work made from a sitting by the subject with the enameller. This was common practice in the early 18th century and allowed the sitter to obtain a durable miniature version of a large oil portrait without having to endure another sitting with another artist.