in the early days of lithography, a smooth piece of limestone was used (hence the name "lithography"—"lithos" (λιθος) is the ancient greek word for stone). after the oil-based image was put on the surface, a solution of gum arabic in water was applied, the gum sticking only to the non-oily surface. during printing, water adhered to the gum arabic surfaces and avoided the oily parts, while the oily ink used for printing did the opposite.