This portrait is painted in enamel on metal. The advantage of enamel over traditional miniature painting (watercolour painted on vellum or on ivory) is that it does not fade when exposed to light. But the process of painting enamels is less free than miniature and is fraught with danger. The first colours to be laid on the metal support have to be the ones that need to be fired at the highest temperature. Then more colours are added and the enamel is re-fired. The process ends with the colours that need the lowest temperature. Such labour meant that it was an expensive option.

This enamel is by Jean Petitot, who was trained as a goldsmith and jeweller. Petitot formed a lifelong friendship with the enameller Jacques Bordier. Together they developed the art of painting portraits in enamel, using a previously unexplored range of colours and subtlety of tone. Petitot introduced this novel art to the court of Charles I in England in the late 1630s. It is not known when he returned to France, but he was there in 1650 and it is likely that he left England before the execution of Charles I in 1649. Thereafter he practised in France, painting many portraits of Louis XIV (ruled 1643–1715), his children and those connected with his court.

This enamel is supposed to depict Louis XIV's daughter by his mistress Madame de la Vallière. Mademoiselle de Blois was born in 1666. If this is by Petitot senior, who died in 1691, she could be no older than 25. And yet it appears to be the portrait of a middle-aged woman. Mademoiselle de Blois was also supposed to be very blonde.