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.

This enamel is by Jean Petitot, a goldsmith and jeweller. Petitot and his friend, the enameller Jacques Bordier, together developed the art of painting portraits in enamel using a previously unexplored range of colours and subtlety of tone. Petitot introduced the court of Charles I in England to this novel art in the late 1630s. It is likely that he left England before the execution of his patron, Charles I, in 1649. Thereafter he practised in France, painting many portraits of Louis XIV, his children and those connected with his court.

This enamel was formerly thought to be of Marie Thérèse, Queen of France from 1643 to 1715. Now it is thought to be of her daughter-in-law, Mary-Anne-Christine of Bavaria (1660-1690), wife of Louis De France, ‘Le Grand Dauphin’ (1661-1711).