This image shows the stages of varnish-making, including several heating stages. Some take place in a water bath while others are carried out over a direct fire—but still protected from it. Source: Fabricant de vernis pour bâtimens, meubles, voitures, &c. From Encyclopédie méthodique - Recueil des planches, vol. 4. (Paris, 1783), plate I.

From The creation of color in eighteenth-century Europe by Sarah Lowengard