Mud—and the clay in it—is one of the oldest beauty ingredients in existence—it’s been used forever in face and hair masks, not to mention the good old multi-functional Aztec Healing Clay. People favor the ingredient for its ability to absorb excess oils and deep-clean pores. But what happens if you wash your oil-prone hair with clay? Would it provide the same squeaky-clean benefits as a clay face mask? I went on a mission to find out.