In stone lithography, what substance is used for drawing on stone?

In stone lithography, the drawing on the stone is accomplished using an oil-based substance, which allows for the creation of images that can then be transferred onto paper through a printing process. The technique specifically utilizes a greasy medium to create an image on a specially prepared limestone surface. This oily medium interacts with the water and the stone in such a way that the drawn areas accept ink while the unmarked areas repel it, which is essential for the printing process.

Using oil-based inks is crucial, as they adhere to the oily drawing and separate cleanly from the wet areas of the stone. Other drawing materials like watercolor, graphite, or charcoal do not possess the necessary properties to achieve the chemical reactions required to successfully create prints in this process. For instance, watercolor is water-soluble and would wash away rather than adhere to the stone; graphite and charcoal, while they can create marks, do not have the oily composition that facilitates the needed interaction during printing.

Thus, the choice of oil-based ink as the correct answer reflects its fundamental role in the lithographic process, allowing artists to create versatile and expressive prints.