2020 Essays

Sulfuric Acid for the Scribe

Clemens, Olivia Ellen

Oil of sulfur, composed primarily of sulfuric acid, is a corrosive mineral acid with many applications. In Ms. Fr. 640, however, the material is almost exclusively mentioned on a single folio (fol. 46r–v) in a series of recipes possibly copied from a source referred to as “Urb.” This essay studies and recreates a selection of these recipes, focusing on those in which oil of sulfur is used as a material for a scribe—as an invisible ink, in creating openwork in paper, as a cleaning agent for quills, and for removing ink from parchment. While numerous contemporary books of secrets include recipes for invisible inks and ink removal, often requiring acids like citrus juice, no other known sources specifically use oil of sulfur for these purposes. This novel application of oil of sulfur serves as a valuable case study of the use of mineral acids in early modern craft processes, as well as early modern techniques for invisible ink and erasure.