The earliest humans discovered that charcoal could be used for painting. Long before the invention of writing, humans used charcoal to paint. Toner or charcoal murals can still be seen in European caves.
In the Middle Ages, people began to discover that lime and water could be used to make block-shaped objects, which could be recorded on dark or hard surfaces using methods similar to charcoal pens. (Paper was a very expensive item in those days, and it was easy to blur with a charcoal pen carved on wood and rock).
It is difficult to verify who first thought of this idea, but at the earliest, the role of chalk was definitely not used for teaching. To be widely used in teaching, the blackboard is more important than the chalk.
Before the 19th century, black lacquer was used to coat wooden boards to protect them from erosion. It is also used to announce important matters, and compare the role of similar bulletin boards. But "blackboards" back then were small and not intended for teaching. But in the middle of the 19th century, universities all over the world began to flourish. The original teaching method of teacher dictation and student dictation became more and more inconvenient due to the increase in the number of students. Therefore, in Europe and the United States, the original teaching method began to be widely used. Small, non-stationary black bulletin boards have been enlarged for teaching purposes to facilitate remote students to copy the teacher's dictation.
Therefore, after nearly two hundred years of slow evolution, education, which was originally extremely difficult to popularize, has finally been transformed into a convenient tool, allowing more students to acquire enough knowledge to eliminate the illiterate and ignorant public. There are two main types of chalk used in China: ordinary chalk and dust-free chalk.
