Chalk is a widely used stationery in daily life, which is generally used to write on the blackboard. Ancient chalk was usually made of natural chalk, but now it has been replaced by other substances. The main component of chalk is calcium sulfate, which is a white precipitate, not easy to decompose, and its particles are larger than dust.

There are two kinds of chalk used in China: ordinary chalk and dust-free chalk. Their main components are calcium carbonate (limestone) and calcium sulfate (gypsum), or contain a small amount of calcium oxide. The earliest humans discovered that charcoal can be used for painting. Long before the invention of writing, people painted with charcoal, and carbon powder or murals made of charcoal can still be seen in caves in Europe.

Introduction to chalk history

In the Middle Ages, people began to find that with lime and water, huge objects could be made and recorded on dark or hard surfaces in a way similar to charcoal pens. At that time, paper was a very expensive item, and it was easy to blur the lettering on wood and rocks with a carbon pen.

It is difficult to prove 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, blackboard is more important than chalk.

This slow evolution of nearly 200 years has finally turned the education that was extremely difficult to popularize into a convenient tool, which has enabled more students to learn enough knowledge and swept away the illiterate and ignorant masses. There are two kinds of chalk used in China: ordinary chalk and dust-free chalk.