How did Jean I Toutin improve enamel portrait miniatures in the 17th century?

In the 17th century, French enamelworker Jean I Toutin revolutionized the creation of enamel miniatures by developing a new painting technique.12

Prior to his innovation, artists relied on small gold bands or surface indentations to keep different colored pigments from blending during the firing process. Toutin discovered that when colored enamels were applied to a previously fired white enamel ground, they would not run together upon refiring.1

This breakthrough allowed artists to apply enamel to a surface with the freedom of painting on canvas and enabled the use of a much broader color palette. By eliminating the need for physical separators, Toutin’s method achieved a new level of precision in color and detail, making the production of high-quality portrait miniatures possible. His technique became highly influential, spreading across Europe as students traveled to learn from him, eventually leading to the widespread popularity of enamel portraiture among royal courts.1