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One mistake could ruin the entire block, and once used the block became useless, because it was unique.
In the Song Dynasty (960-1279) a man called Bi Sheng had the idea of carving individual characters on small, identical square pieces of clay, which was hardened by slow baking.
During the Tang Dynasty (618-907) the technique spread across Asia, through Philippines, Vietnam, Korea and Japan..
But although it was a great advance, this block printing technology had a serious drawback.
It was used to spread Confucian knowledge and Buddhist sutras.
Modern paper is still made from rags and wood pulp.This became known as block printing, and was very similar in concept to the Chinese seal.This technology produced the first ever book with a verifiable printing date in 868. This was nearly 600 years ahead of the first printed book in Europe.But it was an improvement over the materials previously used for writing on, like bone, wood and stone.The invention of paper as we know it came in China around 105 AD.