What type of tool is used to incise lines onto a prepared surface in Silverpoint drawing?

In Silverpoint drawing, a silver-tipped instrument is specifically designed for incising fine lines onto a prepared surface, typically coated with a special ground such as gesso. The technique involves using a tool that has a silver point, which leaves a mark on the surface as it interacts with the prepared medium. This method relies on the unique qualities of silver, which oxidizes and can create a subtle range of tones and textures, making it ideal for delicate line work. The precision of a silver-tipped instrument allows artists to achieve intricate details that are characteristic of Silverpoint art.