By Cheongju Early Printing Museum
Cheongju Early Printing Museum
The world's first movable metal type was invented in Goryeo dynasty. We will learn how to make movable metal type of Goryeo, as well as the process involved, by watching master craftsman Im In-ho restore over 30,000 of Jikji’s movable metal types using the beeswax casting method. Im In-ho is designated national intangible cultural heritage as master craftsman of movable metal type.
How to Make Movable Metal Type of Goryeo Dynasty
From 2011 to 2015, Cheongju Early Printing Museum restored over 30,000 movable metal types of Jikji using the beeswax casting method. Beeswax casting is the process by which types are made: A model is first made from beeswax of refined honeycomb residue, which is then covered with mold paste. This is followed by melting out the beeswax and pouring molten metal into the mold. There is no written record of movable types being made by beeswax casting, but this method was applied through analysis of the printed condition of the main text of Jikji.
Making Beeswax Characters
A strip of paper with model characters written on it is pasted face down on a bar of beeswax made of refined honeycomb residue. Each character is carved in relief on the bar, and then separated to create individual pieces of beeswax characters. Beeswax had been widely used in temples to make metal objects because it transforms quickly with temperature. In another movable type casting called “sand casting,” movable wood types were used as model characters instead of beeswax characters.
Manufacturing of model characters is a very important process because that determines the typeface of a publication. Even more, types were used for a long time to publish many books once they were created. Famous calligraphers of the day were requested to write model characters, or or preferred font characters from existing publications were used as model characters.
After a strip of paper with model characters written on it is pasted face down on a bar of beeswax, slightly heated thin metal knife is used to rub the model characters onto the beeswax bar in order to make the two stick together.
Care must be taken when carving in relief because strokes of a character can be easily damaged due to the plasticity of beeswax. Because movable types are made by melting out beeswax characters and then filling the negative space left by beeswax with molten metal in beeswax casting, replacing a character would require making another beeswax model of the same character, which makes it impossible for the new character to be exactly identical to the first one. This is one of the evidences supporting the claim that Jikji was printed with movable types made by beeswax casting.
Creating a Beeswax Tree
Beeswax tree is made by affixing a thin beeswax rod to the back of each beeswax character, which is then attached to a thick beeswax cylinder that acts as the tree trunk. When doing this, beeswax rods are attached to the trunk at an angle with the characters facing up so that the rods later provide paths for molten metal to flow to the negative space where beeswax characters used to be.
Heat is applied to one end of the beeswax rod to attach it to the back of a beeswax character. Beeswax rod is made in the shape of an awl, with the small tip attached to the beeswax character. If made thus, the pressure of molten metal at the rod’s wider end allows molten metal to flow smoothly into the negative space left by beeswax characters when molten metal is poured in. This will help separate movable type from the metal tree later.
The smaller beeswax rod with beeswax character is attached at regular intervals to the side of a thick beeswax cylinder that acts as the tree trunk. 100 to 150 beeswax characters can be attached to a beeswax cylinder at a time.
Molding flask is made of bamboo to prevent mold paste, which fills the space around the beeswax tree, from dripping down. Because mold should be made of a substance that allows gas to escape easily when molten metal is poured into it, a mixture of clay powder, sand, and ocher is used in appropriate ratio.
A thin coat of mold paste is first applied on the beeswax tree with a brush so that the mold will be completely filled, including the narrow space between the strokes of each character of about 1 cm in size.
Bamboo molding flask is placed securely on the floor to immobilize it after a beeswax tree is inserted in it. Molding flask is made in a cylindrical shape to allow even distribution of heat throughout the mold when beeswax within is melted out in the kiln. Heat may not be distributed evenly in a molding flask of a different shape because heat flows in one direction in a traditional kiln.
Molding flask is filled with mold paste. Care is taken to avoid damaging the beeswax tree and to fill all space evenly between the tree branches.
Mold is dried in the shade for 20-30 days to harden it completely.
Removal of Beeswax from inside the Casting Mold
When the mold is hardened completely from sufficient drying, the mold is put inside a kiln to melt all beeswax inside it. At this time, the kiln is heated for 5-6 hours and the temperature inside it is maintained at about 900°C.
When beeswax is removed completely, a cavity is created inside the mold where beeswax used to be. This makes molten metal flow easily because runners are positioned downward.
Pouring of Molten Metal
Molten metal, melted at 1,000°C to 1,200°C, is poured into the mold. It smoothly and evenly throughout the mold when the temperatures of both te molten metal and the mold are similar. In Joseon dynasty, copper, lead, tin, zinc, and iron were used to create alloys for the production of actual movable metal type, with copper being the principal component at around 80%. Thus, movable metal type was sometimes called movable copper type. The main components of molten metal used in the restoration of these movable metal types are copper (80%) and tin (20%).
Due to the fact that a small amount of metal is used at one time, metal is melted in a small furnace.
Metal is melted at a temperature of 1,000°C to 1,200°C.
When molten metal cools within the mold, the hardened mold surrounding the metal tree, which is composed of movable types, is hammered away and any mold remaining between the crevices of the metal tree is thoroughly brushed away with a metal brush. A metal tree with movable types that looks identical to the original beeswax tree is finished.
Beeswax casting is a suitable method for making three-dimensional objects. More elaborate movable types can be made by it than sand casting.
Molten metal sometimes finds its way into gaps and form excrescences on the typeface if mold paste does not fill the molding flask completely and evenly.
Finished Movable Type Pieces
Movables type pieces are finished when types attached to the tips of a metal tree are separated and typefaces rubbed against a fine grindstone after the mold is removed. Finished movable type pieces are separated individually and stored in a type case for convenience. During the Joseon dynasty, between 100,000 and 300,000 movable type pieces were typically made when making a font. The greater the number of type pieces, the greater the efficiency in printing because many printing blocksformes can be typeset at the same time.
Metal types attached to the tips of the metal tree are separated with a hacksaw or string.
Excess parts such as metal excrescences on newly finished movable types are removed, and the typeface in relief is then smoothed by rubbing them against a fine grinding stone. Care must be taken to avoid rubbing the typeface too hard as this leads to thicker strokes.
When a book is to be printed, movable types are composed and put into a galley according to the original manuscript, then securely fastened. Typesetting is finalized after repeated test prints and correction of mistakes are made on the printing block. Typesetting is one of the most difficult tasks in printing. This task is done by a typesetter. It is such an important process that the typesetter’s skill determines the quality of the printed matter.
Because the size and shape of movable types are not uniform, types should be made similar in height, direction, and spacing, and they must be securely fastened during typesetting to prevent the types from moving. Once the initial typesetting is completed, a test print is run and the typeset corrected and reprinted according to the proof. This process of test printing and correcting is repeated three times or more for final typesetting.
Molten beeswax is poured on the printing block to fasten movable types, thus preventing them from moving when printing. Bamboo pieces or wet paper were also used in Joseon dynasty to stabilize movable types.
After ink is evenly applied to the printing block, required number of copies is printed. The printing block is then taken apart when printing is finished, and the movable types are cleaned and placed back in their original position for use in printing another page. Because movable type printing goes through the process of typesetting, printing, and dismantling repeatedly, a printing block cannot be stored and used for reprints as with woodblock printing. Oil soot ink, which is made from the soot collected by burning vegetable oil, is used in movable metal type printing because it adheres well to metal surface.
Oil soot ink must be used in movable metal type printing. Oil soot ink is made from the soot collected by burning vegetable oil. Common ink does not apply evenly to the metal surface of types; water droplets form on metal surface. For woodblock printing, pine soot ink is used.
Mulberry paper that has been cut into a specific size is put on the inked printing block.
A page is printed by rubbing the mulberry paper with a rubbing pad against the printing block. Rubbing pad is made of animal fur or hair tied together.
Only the required number of copies are printed per printing block. Extras are printed in consideration of possible mistakes that might occur during the binding process because it would be inconvenient to typeset the page again for reprinting later.
After it is printed, the paper is folded in half at the block center with the printed side facing the outside. The remaining sheets are also folded in sequence until enough sheets are gathered to make a volume. To this are added front and back covers with ogival motif, and then five holes are drilled along one edge. A book is created when the sheets are tied together with strings through the holes. This binding method is called string binding, which appeared in the Joseon period. Popular binding methods of the Goryeo period are scroll binding, concertina binding, wrapped-back binding, and whirlwind binding.