While perhaps not quite as frightening as the famous Alfred Hitchcock shower scene, just imagine the shock of stepping into a hot shower, unwrapping your favorite bar of soap and discovering that it is already dirty. It can happen.
That is because soap contains glycerin, which brings with it important moisturizing properties. During the manufacturing process, glycerin is added to the soap formulation before it goes to final production. The temperature control during manufacturing must be precise, with little margin for error. When the temperature is not controlled properly, the soap can turn brown and even form brown specks — small but still very much noticeable. That is hardly the 99 and 44/100ths percent pure that a good soap needs to be.