According to the relevant data of Life Encyclopedia, the black signature pen is a ball with a diameter of 0.5 mm, and the writing is a black water-based pen, including water-based signature pen and oil-based signature pen. Water-based pens are generally used for paper, while oily pens are generally used for sample signature or other permanent marks, which are difficult to wipe.
Signature pens can also be divided into broad sense and narrow sense. Broadly speaking, pens used for signature are all called signature pens. For example, Parker's signature pen and Montblanc's signature pen, which are often used now, are all pens that we have been using since childhood. In a narrow sense, it refers to carbon ink pen or above, while the exam uses a narrow signature pen, that is, carbon ink pen.