Chemical principle: Because carbon (chemical formula C) is chemically stable and generally does not react with air, articles written in carbon ink can be preserved for a long time. For example, China's ancient calligraphy works have been preserved to this day because of carbon in ink. ?
According to the records, carbon ink was used. Therefore, it is best to use carbon ink. In the morning light, the oily pen is not only difficult to fade, but also smooth and convenient to write.