Movable Metal Type: Great Invention of Korea

Tour a master craftsman's workshop and learn about a traditional way of making movable metal type.

Movable Metal Type of JikjiCheongju Early Printing Museum

The invention of movable metal type played a key role in the development of printing and advancement of human knowledge. The oldest existing book to be printed using this technology was Jikji, an anthology of Buddhist teachings.

Jikji (restored print)Cheongju Early Printing Museum

The invention of movable metal type played a key role in the development of printing and advancement of human knowledge. The oldest existing book to be printed using this technology was Jikji, an anthology of Buddhist teachings.Printed in 1377 during the Goryeo Dynasty, Jikji is now a part of UNESCO’s Memory of the World. There are several ways to make movable metal type. This tour of a master craftsman’s workshop will take you through one process using wax casting.

Making Wax Letters

First, the master craftsman hardens purified wax into a long bar shape. Letters are written on a thin piece of paper which is placed face down on the wax bar. The master craftsman carves the letters and then cuts them into individual wax types. 

The types are carefully polished and attached to wax sticks called “branches” which are later attached to a tree trunk-like wax rod. They become the building blocks of the casting process.

Carving Letters

The wax bar allows the master craftsman to create precise and intricate three-dimensional types with a carving knife. The bar is cut into individual wax types and carefully polished to create what are called the “matrices.”

Wax Rods

The master craftsman attaches the wax matrices to a cylindrical wax rod to form branches of letter types. These branches are tilted at an angle so that the molten metal will flow smoothly into the mold once the wax is removed.

Wax Casting and Sand Casting Method

In wax casting, wax types are encased in a clay mold and fired. The wax melts away and molten metal is poured into the hollow space left behind by the wax. In sand casting, wooden types are used to make casts out of molding sand. Molten metal can then be poured into the cast.

Making the Mold

The master craftsman places the wax branches inside a bamboo container. Then he fills the container with a thin mixture of red clay and other materials to make a mold. The mold is left to dry in the shade for 20 to 30 days until it solidifies completely.

Filling the Cast with Clay

The master craftsman makes sure the bamboo container and wooden base are firmly attached before pouring the mixture of red clay, sand and other materials into the cast. When the cast is full, the craftsman shakes it to remove air from the clay mixture.


Once the clay mold is formed, it has to dry in the shade before it can be fired. After the wax branches melt away, the remaining mold is used to create the final metal types. During this step, a small, premade hole in the mold allows the smooth flow of molten metal.

Removing the Wax and Injecting Molten Metal

The master craftsman puts the dried and hardened mold into the kiln. He closes the entrance of the kiln with bricks and red clay to make sure the kiln heats up enough to completely melt away the wax inside the mold. 

The wax leaves behind a cavity that is filled with molten metal. As the metal cools, it hardens into the exact shape of the wax branches. Then the branches are broken into individual types.


The kiln is completely sealed with red clay, allowing the molds inside to reach extremely high temperatures. Only the wax melts away while the evenly heated molds harden like ceramics.

Firing the Mold

When the dry, hardened mold is fired, the wax branches inside melt away and create a cavity in the same shape. The master craftsman injects molten metal into this space to make movable metal types.

Injecting Molten Metal

When heated for about two hours at 1,000 to 1,200 °C, solid metal turns into liquid. At this point, the master craftsman can pour the molten metal into the cavity of the mold which has been placed on a flat and level wood or iron plate.

Polishing Movable Types

Once the molten metal cools down, the master craftsman breaks the mold to separate the branches of metal types. Then he uses a hacksaw or fretsaw to separate the individual types from the branches and remove excess metal parts. He polishes the surface of each movable type with a smooth whetstone or sandpaper to produce the final types.

He polishes the surface of each movable type with a smooth whetstone or sandpaper to produce the final types.

Number of Movable Types

The master craftsman might use the same letter more than once to finish one typeset. He needs to have multiple types for frequently used letters. The more types he has, the more efficient the printing process becomes.

Movable Types Cabinet

When not in use, the types are stored in a specially designed cabinet. The cabinet has numerous compartments, and each compartment is labeled to indicate which letters the drawers contain.


The completed types are sorted and stored in a cabinet. When the master craftsman is ready to print, he begins with a typesetting board. Individual types are arranged on the board to fit the desired size of the manuscript or book.

At this point, the height and angles of the types should be aligned perfectly, so that the print comes out evenly. It is a process that requires a high level of skill. Lastly, melted wax is poured onto the board to hold the types in place.

Copper Boards and Typesetting

The master craftsman uses a copper typesetting board. After arranging the types, he pours melted wax into the gaps to fix the types in place. To make adjustments after the wax has hardened, he can melt it again and rearrange the types as needed.

Gyunjajang, Type Leveling Master Craftsman

Historically, the 'type leveling master craftsman' called gyujajang played a key role in making sure the types were evenly spaced and neatly arranged. Well printed books and manuscripts depended on his skill and expertise.

Miscellaneous Tools

The master craftsman uses various tools to make movable metal types. These include sculpting knives for intricate carvings, a brush made of wax and human hair to rub paper against the typeset, and a hot iron to melt wax and fix it in place.


After all adjustments and corrections are made, the typeset is complete and the master craftsman can print as many copies as he likes. This is arguably the most important step in the book making process.

The master craftsman spreads ink evenly over the completed typeset, places traditional Korean paper called hanji over it, and rubs down the paper to print. During the process, he needs to be meticulous about keeping the types level and straight. 

After printing, the master craftsman disassembles the typeset, sorts the types by character, and stores them for future use.

Ink Selection

Metal type printing mainly uses ink made out of burnt vegetable oil while woodblock printing uses ink made from pine soot.

Correcting Printing Errors

The actual printing begins only after the process of typesetting-test printing-paper correction-typeset correction is repeated and results are satisfactory. 

When errors occur despite such efforts, the mistake is either cut out and replaced or a correction is added next to the mistake.

Preparing for Binding

Once the printing is finished, the master craftsman folds the printed sheets in the middle and makes five holes to bind them. This 'five-hole side stitch' was one of many Asian bookbinding methods, and the most commonly used style in Korea.

The Merits of Hanji

Hanji is a traditional Korean paper made from the paper mulberry plant. It has long been praised for its durability, breathability, and insulation properties. Hanji was used to print Jikji as well as the Silla Dynasty text The Great Dharani Sutra which has been preserved for some 1300 years.

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