Bi Sheng and Movable Type

In the old days, one slip of the knife could ruin a printer's whole page. If a single character was carved wrong, the page had to be carved again from the very beginning.

It sounds like a small thing at first. Only after a moment's thought does the difficulty show.

To print a page, people first wrote it out on thin paper. The sheet was laid face down and pasted onto a wooden board. The ink soaked through the paper and showed in reverse on the wood. With a knife, the carver cut away the wood around every stroke, until the whole page of characters stood up in relief like a tiny field. Ink it, lay paper on top, rub gently, lift it off, and there was a page.

The method was handsome and it lasted. Printing in China dates from about the year 600, and this way of carving boards was used for several hundred years. A well-carved board could print thousands of copies with its strokes still sharp.

The trouble was that the board was one solid block of wood. What was cut away could not be put back. There is no eraser for wood.

A page held hundreds of characters. The carver sat hunched over it for days, his knife moving from one character to the next. Then, on the afternoon of the fourth day, on a line near the bottom, the blade slipped a little.

That was the end of it. Not one character ruined, but the whole board. A fresh piece of wood came out, and the work began again from the very first character.

So this was a problem every carver knew from the inside. Each one answered it by being more careful still. But no matter how careful a hand is, some day it grows tired.

Sometime between 1041 and 1048, one man answered that problem in a completely different way. He lived under the Song, the dynasty then ruling China. His name was Bi Sheng.

Later generations knew almost nothing about him. He held no title, and the official records contain not a single line about him. The old writings call him simply a man in plain cloth, an old way of saying a commoner.

His method began with the cheapest thing in the workshop. Clay.

He took soft clay, shaped it into small blocks, and carved exactly one character on each. Not a whole page. Just one character. Each piece was as thin as the rim of a coin. Then he fired them. In the heat, the clay hardened into stoneware that would not warp or crumble.

Then came the best part.

He prepared a flat iron plate and spread on it a mixture of pine resin, wax and paper ash. On top of that he set an iron frame.

One by one, the fired characters were taken from their compartments and placed in the frame, shoulder to shoulder, row after row. When the frame was full, the whole tray of type looked like a single solid block.

Now he held the iron plate near the fire. The coating underneath grew warm, softened and began to run a little. The workshop smelled of heated pine resin, a little sharp and a little sweet. He laid a flat board on top and pressed down. Characters standing at uneven heights sank until they were all level, as smooth as polished stone. He lifted the board away and let the plate cool. The coating set again and held every character fast.

Ink. Paper. A gentle rub. And the page appeared.

And this is where the old problem finally found its answer.

When the printing was done, he warmed the iron plate over the fire once more. The coating softened a second time and let go. Each character came away from the iron whole, without a single stroke chipped. He picked them up, wiped them clean and put them back in their old compartments. The next morning, those very same characters would stand together as a completely different page.

It meant that one wrong stroke no longer dragged the whole page down with it. If a character was wrong, only that character came out, and another went in. The rest of the page stayed exactly where it was.

The remaining details show that he really did this work, and on a large scale.

For the most common characters, he made 20 or more copies in advance. Characters not in use were labeled with paper tags, sorted by rhyme and stored in wooden boxes. When he met a rare character he did not have, he carved it on the spot and fired it quickly over a burning wisp of straw. In moments it was ready to use.

He also used two iron plates in turn. While one was printing, the other already had its type set for the next page.

He did not make his characters from wood. Wood grain is dense in some places and loose in others, and when it gets wet it swells unevenly, leaving the characters at different heights. Worst of all, it stuck to the coating and was very hard to remove. Fired clay had none of those faults.

What came next is brief.

Then he died. He was not famous in his lifetime.

This part is worth a pause. Bi Sheng was a commoner. He had no office that would oblige anyone to record his name, and no historian following him. If things had gone the usual way, even his name would have vanished with the ashes in the kiln.

His story survives today because of someone else. Some decades later, there was an official named Shen Kuo. He was curious about everything and liked to write down how people made things. In his old age, around 1088, he wrote a book of miscellaneous notes called the Dream Pool Essays. Among its hundreds of entries is one short passage. It describes how a commoner named Bi made his movable type.

A few lines. Truly just a few lines. Everything the world knows about Bi Sheng fits into those lines, and all that has been told here comes from them.

Shen Kuo added one more sentence at the end. After Bi Sheng died, his clay type passed to members of the writer's own family, who kept it as a treasure.

Vietnam also has a craft that lives by carved boards, and it survives to this day.

In Đông Hồ village in Bắc Ninh, craftspeople carve their pictures on wooden boards, one board for each color. The boards are made of thị wood or thừng mực wood. Families know the chicken and pig pictures from Tết, the Lunar New Year festival in Vietnam. Each one is printed in five colors in turn. Red goes first, then green, yellow and white. Last of all comes the black outline board, which makes the picture clear.

Here, the solid board is exactly what is needed. A character can be taken apart. A chicken flapping its wings cannot. Its lines must run unbroken across the wood for the picture to come alive. The people of Đông Hồ keep the board, and with it the carving hand that is never allowed to slip.

On December 9, 2025, UNESCO inscribed the craft of Đông Hồ folk painting. It became the 17th element of Vietnam's intangible cultural heritage to be inscribed by the organization.

Two crafts, two different problems, and two answers that are both right.

Now take a small name stamp, the kind sold in bookshops: dip it in ink, press it onto paper, lift it up. The stamp is still whole, and this afternoon it can press its mark again.

The first person to think of setting thousands of tiny stamps like this into a page, then taking them apart and setting them again as a new page, was a craftsman in plain cloth. He lived nearly 1,000 years ago. He never saw how far his work would travel, and he very nearly lost his own name too.

That name is Bi Sheng. And just now, it has been spoken aloud one more time.