Ancient Roman laundrymen plied their trade under the patronage of the goddess Minerva, whose symbol, the owl, perches on a wicker frame in this fresco from Pompeii’s largest laundry. (Soiled clothing in need of bleaching was placed on a conical frame over a smudge pot with burning sulfur.) The entire laundry process was a noisome affair. Containers standing outside the laundries served as convenient urinals for male passersby and provided launderers with a key ingredient in first-century A.D. detergent. Human urine was combined with potassium carbonate (or potash, from wood ashes) and mixed with hot water in large tubs. […]