A crayon (, , or ) is a stick of colored wax, charcoal, chalk, or other materials used for writing, coloring, drawing, and other methods of illustration. A crayon made of oiled chalk is called an oil pastel; when made of pigment with a dry binder, it is simply a pastel; both are popular media for color artwork. A grease pencil or china marker (UK chinagraph pencil) is made of colored hardened grease and is useful for marking on hard, glossy surfaces such as porcelain or glass. Some fine arts companies such as Swiss Caran d'Ache manufacture water-soluble crayons, whose colors are easily mixed once applied to media.