Placing Dawn dish soap in a bathtub overnight is a popular household cleaning and maintenance trick frequently recommended to break down stubborn ring-of-the-tub grime, body oils, and soap scum without requiring abrasive scrubbing. The powerful surfactants and grease-cutting agents in the dish soap penetrate accumulated films while sitting overnight, allowing homeowners to easily rinse away tough residues the following morning and leave porcelain or acrylic bathtub surfaces sparkling clean with minimal physical effort.