The grease pencil, a wax writing tool also known as a wax pencil, china marker or, especially in the United Kingdom, a china graph pencil, or nerd pen in Germany, is a writing implement made of hardened colored wax and is useful for marking on hard, glossy non-porous surfaces such as porcelain, glass, polished stone, plastic, ceramics and other glazed, lacquered or polished surfaces, as well as the glossy paper that is used for photographic printing (particularly for contact sheets), x-rays, and for marking edits on analog audio tape and film. It is also used to label theatrical lighting gels. It is often used as a construction or handyman's marking tool as it rarely scratches the surface it is used on. It may be used to mark a wet surface. They are also favored among some traditional artists. Due to its ability to write on glass, it is often used in chemistry labs to mark glassware.