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.

In the 1630s Jean Petitot, goldsmith and jeweller, and his friend Jacques Bordier, an enameller working at the English court of Charles I, together developed the art of painting portraits in enamel using a previously unexplored range of colours and subtlety of tone. This French work by an unknown artist is dated 1645 and is contemporary with the early work of Petitot. Interestingly, it has a monochrome style rather than the newly fashionable high-colour methods pioneered by Petitot and Bordier.