What is the primary medium used in lithography to produce images?

The primary medium used in lithography to produce images is indeed a greasy medium like crayon or ink. Lithography is a printmaking technique based on the immiscibility of oil and water. The process involves drawing an image with a greasy substance on a flat stone or a metal plate. When the surface is treated with a chemical solution, the areas with the greasy drawing repel water and attract oil-based inks, allowing the image to be transferred onto paper during printing.

This unique characteristic of using a greasy medium is what differentiates lithography from other printing methods. For instance, oil paint, watercolor, and charcoal do not share the same chemical properties necessary for lithographic processes. Oil paint and watercolor are typically used in different forms of painting, while charcoal is more associated with drawing and sketching rather than printmaking techniques like lithography. The ability of lithographic materials to interact with water and oil is what makes the greasy medium essential for creating clear, distinct prints.