to those used in fountain pens and rollerball pens. Brush pens might be either refillable or disposable, and might use either water-based or waterproof ink. The most significant functional difference of brush pens from felt-tip pens is the far greater compliance of the tip. Brush pens are an obvious alternative to ink brushes for Chinese calligraphy and Japanese calligraphy, but are now also commonly used in other forms of calligraphy and by artists such as illustrators and cartoonists. The primary appeal of these pens to such artists is that they allow a great deal of line width variation in response to small changes in applied pressure. A stylus pen, plural styli or styluses, is a writing utensil which does not use ink, but rather makes marks primarily by creating scratches or indentations in the writing surface. As such, the tip often consists simply of a sharp metal point. Such tools are also used for other types of marking than writing, and for shaping or carving in, for example, pottery. The word stylus also refers to a pen-shaped computer accessory that is used to achieve greater precision when using touchscreens than generally possible with a fingertip. There are products available that combine a ballpoint tip at one end and a touchscreen stylus at the other. Historic These historic types of pens are no longer in common use as writing instruments, but may be used by calligraphers and other artists: A dip pen (or nib pen) consists of a metal nib with capillary channels, like that of a fountain pen, mounted on a handle or holder, often made of wood. A dip pen is called such because it usually has no ink reservoir and must therefore be repeatedly dipped into an inkpot in order to recharge the nib with ink while drawing or writing. The dip pen has certain advantages over a fountain pen; it can use waterproof pigmented (particle-and-binder-based) inks, such as so-called India ink, drawing ink, or acrylic inks, which would destroy a fountain pen by clogging, as well as the traditional iron gall ink, which can cause corrosion in a fountain pen. Dip pens are now mainly used in illustration, calligraphy, and comics. A particularly fine-pointed type of dip pen known as a crowquill is a favorite instrument of artists such as David Stone Martin and Jay Lynch, because its flexible metal point can create a variety of delicate