These magnificent ewers are of a particularly rare and striking type of opaline glass known as 'gorge de pigeon', which was also referred to as 'rose hortensia'. Opaline glass, which should more correctly be termed 'cristal d'opale', is formed from a type of lead crystal which is then coloured by the addition of other substances. In the case of 'gorge de pigeon', the colour is formed by the addition of particles of gold and pewter, which accounts for its rarity.

These splendid ewers are particularly early examples of the coloured 'cristaux d'opale' which first appeared in the Empire period when the celebrated Baccarat factory was established. Baccarat rivalled and rapidly eclipsed the output of the English and Bohemian manufacturers, which until then had dominated the production of crystal glass. The taste for such coloured opalines was particularly marked in the Restauration period. The Journal des Dames et des Modes in January 1824 for instance remarked that 'On a donné aux dames, en cadeau de Jour de l'An, beaucoup de cristaux colorés en blanc laiteux dit opale; en rose dit hortensia, en bleu dit turquoise...'(see S. Faniel ed., Le Dix-Neuvième Siècle Français, Paris, 1957, p. 126).

The 'antique' form of these ewers, with their elegant handles of swan's necks draped in acanthus and grapevines, derives from a drawing for a ewer which appears in plate XVIII of the hugely influential Réceuil de Décorations Interieures of Charles Percier and Pierre François-Léonard Fontaine, first published in 1801.