Ancient Romans used human urine to wash their clothes.

In Ancient Rome, professional laundry workers were called fullones. They worked in shops called fullonicae. You can still see the remains of these shops in the ruins of Pompeii today. Urine was a valuable resource because of a chemical called urea. When urine sits for a long time, it turns into ammonia. Ammonia has a high pH level, which helps it dissolve oils and organic dirt. To clean the laundry, workers mixed the aged urine with water and a special clay. They stood in large tubs and jumped on the clothes to force the mixture into the fabric. This rhythmic treading was called the saltus fullonicus. The demand for urine was so high that Emperor Vespasian created a urine tax in the 1st century AD. People who collected urine from public pipes had to pay the government. When his son complained about the tax, the Emperor famously said that money does not smell. After the urine soak, workers rinsed the clothes in clean water. Sometimes they used burning sulfur to bleach the fabric even more. This was the most effective way to clean heavy wool until modern soaps were invented.