Both European and Asian historical records report that Jesuits were at the origin of enamelling technology transfers from France (and Italy) to Asia during the 17 th century. A mobile Raman setup equipped with a high magnification (x200) microscope objective with long working distance is used to identify the use of European (arsenic-rich) cobalt in 17 th and 18 th century porcelains: twenty soft-paste porcelains from Rouen (L. Poterat' Factory), Saint-Cloud, Paris (Pavie', Hébert', Chicanneau', and Bellevaux' factories), Lille, Mennecy, and Vincennes factories, of which almost all were produced before 1750, belonging to the Cité de la Céramique Collection (formerly Musée national de Céramique, Sèvres), have been analysed in order to get a more representative view of the type of cobalt ore used. A large proportion of blue decors exhibit signs of lead arsenate, even for productions after ~1750, which proves the wilful interest given to arsenic phases in magnifying blue hues. Different lead arsenate signatures are observed, one assigned to the product of reaction of As-rich cobalt ore with lead-based glaze and another characteristic of added arsenic. At least two groups of glaze are identified: a lead-rich one and a mixed lead-alkali glaze. Porcelains made during the second half of the 18 th century exhibit the very strong As-O modes characteristic of the voluntary addition of a lead-arsenate forming compound. Comparisons are made with Qing Chinese productions exhibiting similar Raman signatures and expected to have benefited from transfers of technologies.