Invisible Dry Shampoo This lightweight invisible dry shampoo erases mild dirt and oil with gentle, finely milled volcanic ash, reviving your hair and scalp without leaving it dry or brittle. Gentle enough to refresh styling throughout the day and in between blowouts. What It Is: An invisible, weightless, buildable dry shampoo that uses finely milled volcanic ash for a lightweight cleanse to refresh hair and erase mild dirt and oil.