Johann Heinrich Von Hurter (1734-1799)
Hurter was in Paris before 1776, possibly when the present portrait was painted. In that year he published a book which extolled the virtue of the medium of enamel
Hurter was born in Schaffhausen (German-speaking Switzerland) but by 1777 was settled in London, exhibiting at the Royal Academy between 1779 and 1781. His careful observation of facial features and drapery must be a result of his education with Jean-Etienne Liotard (1702-1789) in Geneva. Like Liotard, he worked in pastel, but his main output was in the medium of enamel - one of his earliest commissions would seem to be the portrait of Prince Wilhelm August von Holstein (1767). From 1770, he began to produce copies after old master paintings, such as his Portrait of a Man with Beret (1774) by Rembrandt van Rijn (1609-1669) – and after contemporary artists such as Sir Joshua Reynolds (1723-1792)...
Hurter was in Paris before 1776, possibly when the present portrait was painted. In that year he published a book which extolled the virtue of the medium of enamel; ‘Prospectus d’un plan de souscription pour une exécution en émail d’un nouveau…’.
From around 1777, Hurter was based in London where his most important patron was Lord Dartrey (1725-1803). Not only did Dartrey commission his own portraits from Hurter but he also introduced the artist to other aristocratic patronage. Hurter then spread his net wider, travelling back to his native Switzerland and Germany, painting the portrait of the Margrave Karl Friedrich von Baden (1728-1811) and, for Catherine the Great, producing a large number of copies in enamel.
In 1787 he returned to England with a new venture, making scientific instruments. Little is known about his activity in this field, although his air pumps, telescopes, sextants, theodolites, planetariums and barometers were used by renowned scientists such as Horace-Bénédict de Saussure (1740-1799) or Johann Georg Tralles (1763-1822). In 1789 he was enobled by the Elector Karl Theodore and after this date very few enamels come to light.
 Information from N. Jeffares, Dictionary of Pastellists (online ed.)
 The most valuable source for information on Hurter’s various commissions are his letters (1787-1790) to the Schaffhausen historian Johannes von Müller (1752-1809)