Soap is made by exposing animal or vegetal fats and oils to caustic alkalis and water. Depending on the raw materials, we distinguish between soft green soap and harder sodium soap. In the early modern period, hard, white sodium soap was made by using soda (sodium carbonate), which was obtained from the ashes of marine plants (barilla, seaweed, etc.), or potash or woad ash (potassium carbonate), which was boiled with pure fats or oils (usually olive oi…