Historical Evolutions of Lead-Fat/Oil Formula from Antiquity to Modern Times in a Set of European Pharmaceutical and Painting Treatises

Abstract

Recipes describing the controlled mixture and reaction of fat/oil with lead-based compounds have been known and employed since antiquity until modern times. Two major fields have developed such practices: pharmacy, for the preparation of lead plasters (i.e., dressings made of lead-based compounds and fat/oil) and related unguents, and painting, for the preparation of thickened oils. Here, we review and analyze a set of almost 500 recipes, from historical texts from the Mediterranean area, dating from Pharaonic Egypt to the nineteenth century. Recipes show similarities (e.g., type of lead ingredients, advice regarding the grinding level of powders, risks associated with overheating the mixtures) and differences (e.g., type of fat/oil, introduction of additional compounds, use of sunlight) which can be explained by the different purposes and applications of the formed pastes: plasters must be soft, with a thick consistency, and adhere to the skin for a long time without drying; conversely, “thickening” oil by reaction with lead-based compounds is intended mainly to speed up drying reactions in paintings. Also, some historical evolutions may be noticed, e.g., the choice of lead ingredients and the progressive replacement of lead-based compounds by zinc oxide for toxicological reasons, the interpretation in chemical terms (in particular the identification of the formed lead soaps and glycerol), and, for lead plasters, the quasi-systematic introduction of water from the eighteenth century and the standardization of recipes.