Early Printing in Korea - 4.1 Metal Movable Type Casting

_{Understanding Korea Series No.2}
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4. The Invention and Development of Metal Movable Type Printing	1) Metal Movable Type Casting	2) Metal Movable Type Typesetting

Korea’s metal movable type printing technology has been recognized as a renowned cultural heritage worldwide, celebrated by the entire world. The irregularities found in the type pieces reveal that the technology at the time was yet to be perfected, and indicate the limited resources of the local Buddhist temples where they were cast. However, the true beauty of world’s oldest extant metal movable type print lies in its importance in cultural history, rather than the physical beauty of the print itself.

The printing technology of Baegunhwasangchorokbuljojikjisimcheyojeol (the Hymn of Monk Baegun and Identification of the Buddha’s Spirit by the Practice of Zen), the only physical metal movable type print of the Goryeo Dynasty still extant, had been handed down to the Joseon Dynasty, and became the foundation for the improvement and development of consequent metal movable types such as Gyemija, Gyeongjaja and Gabinja. The recent discovery of Jeungdogaja has aroused keen interest among the scholars.

There are several known traditional Korean metal movable typecasting methods: wax, sand and kaolin. Casting is done by pouring the molten substance into a mold to create the desired shape, and this method is used not only for metal but also for gypsum, kaolin and glass. Bronze, an alloy of copper and tin, is the primary metal used for the casting of metal movable type. Bronze from the prehistoric Korea is known to be an alloy of seven parts copper, two parts tin and one part zinc. A more general ratio for bronze is about 95-70% copper and 5-30% tin. Impurities such as nickel, zinc and antimony are mixed in as well but their combined amount is usually less than 1%. Copper is alloyed with tin in order to create a stronger metal, but as the amount of tin increases, the color becomes lighter and the metal becomes more brittle.

There is no trace of records about the wax typecasting method related to metal movable type. For the sand and kaolin techniques, the complete formulae are unknown, yet some fragmentary information has been handed down.

There is no record of exactly what type of casting methods were used during the Goryeo Dynasty. But Joseon is known to have used the sand typecasting method from the founding of the Dynasty led by the National Foundry, Jujaso (鑄字所). The kaolin typecasting method was also used towards the end of the Dynasty, mainly among the lay people.

According to up-to-date research, Heungdeoksaja, derived from the re-engraved edition of Baegunhwasangchorokbuljojikjisimcheyojeol, the movable metal type printing of the Goryeo Dynasty, and Jabidoryangchambeopjiphae (慈悲道場懺法集解, the Collection of Prayers for Mercy) were manufactured using the wax typecasting method. This method was traditionally used to manufacture delicate and complex Buddhist objects (佛具類). Wax typecasting for metal movable type is done by carving the letter on one side of a prepared block of beeswax, covering the carved beeswax block with a dough consisting of oto (refractory material used in making crucibles (烏土) and clay into a mold (鑄型), letting the mold dry, baking it and pouring liquefied iron into the mold. The type pieces made of this method are meticulous; however, only one type is created per inscription, making it almost impossible to recreate type pieces with identical fonts or size.

Each letter is made by pouring liquefied iron into a closed space and applying pressure on it, which in turn will inevitably melt the matrix (模本), so only one character can be made for one mold. On the other hand, complex patterns, metal objects with curves such as accessories, complicated parts of copper bells, like the dragon head (龍頭), which cannot be divided in two, may be cast into singular molds.

Wax typecasting can be summarized as follows:

Select the character style and the size
Make master characters with beeswax (蜜蠟父字): create the tree branch-shaped wooden mold from the character model first
Make the tree branch shape with beeswax
Decide on the angle of entry and passageway for liquefied iron
Choose materials to be used as the clay dough (埋沒材料) (Knead the clay mixture)
Fabricate the mold and melt the matrix
Liquefy and pour in the iron
Separate and trim the type pieces

Wax Typecasting :

Wax Typecasting
Melt the beeswax and pour it into rectangular shaped mold panel.
Place the paper with characters on to the wax bar and engrave the characters
Cut the bar into each character piece.
Glue the character pieces to the tree branch shaped beeswax base by applying heat.
Cover the beeswax base with character pieces with clay to make a mold.
Once the mold is hardened heat the mold to melt the beeswax. Melted beeswax will pour out from the mold making a hollow space in the space of the base and character pieces.
Pour melted bronze into the opening of the mold to fill the hollow space.
Cool the bronze and break the clay mold.
Once the mold is completely broken the bronze tree branch base and character pieces will appear.
Using a metal saw separate the character pieces and trim them with a file.
Finished type pieces

Records related to metal movable typecasting methods of Goreyo are scarce, but a relatively large number of records on the Joseon Dynasty’s sand typecasting methods have been passed on. The most frequently quoted historical account in almost all researches dealing with the latter is a record found in Yongjaechonghwa (慵齋叢話, Compilation of Essays by Yongjae) written by Seong Hyeon in the 16th century.^[1] This Joseon-period document is significant, since it contains a detailed record of the traditional movable typecasting process.

The typecasting process begins by inscribing various letters on a piece of beechwood. Next, soft clay mixed with sand found near the coast is spread uniformly and flatly on the printing plate (印板), and the wooden engraved letters (木刻字) are pressed on it to create impressions. After that, two printing plates are combined, and the melted copper alloy is poured into a hole so that the liquid fills in the concave section to form individual type pieces. The pieces are then trimmed several times.

The document also explains the titles and specifies the roles of the casting artisans.

ⓐGakjajang (刻字匠): the Master Wood Engraver

ⓑJujang (鑄匠): the Metal Casting Master

ⓒSujang (守藏): the Master Keeper in charge of storing and maintaining the type pieces in the warehouse (藏櫃)

ⓓChangjun (唱准): the Master Orator who reads out the original writing (書草), is usually able to decipher all the characters

ⓔSangpan (上板): the first typeset made after the master typesetter arranges the type pieces over the original writing

ⓕGyunjajang (均字匠): the Master Typesetter in charge of justifying the typeset when aligning and fixing the type pieces, by filling up the void with bamboo, wood or scrape of paper so they do not shake

ⓖInchuljang (印出匠): the Master Printer in charge of printing the embedded plat

ⓗGamingwan (監印官): the Master Printing Inspector who oversees the whole process, usually an officer from the Royal Ministry of Publication. A separate inspector, a civil administrative officer, was also appointed^[2]

In the Annals of Joseon Dynasty made during King Jeongjo’s reign, an entry about the casting process of Imjinja and Jeongyuja states:^[3] “in the gabin year of King Sejong’s reign (1434) (the King) commanded Kim Don (金墩) and others to melt copper and cast movable types modeled (字本) after Hyosunsasil (孝順事實, Book of Filial Piety) and Wiseoneumjeul (爲善陰騭, the Books on Merits and Demerits), commonly called Wibuinja (衛夫人字), there were 200,000 of them. During the reign of King Seonjo, these types were refurbished (重修), and when the King (Jeongjo) was still residing in the crown prince’s palace (春邸), he ordered his subordinates to amend Gabinja to cast 150,000 characters, known as Imjinja (壬辰字), and printed books such as Gyeongseojeongmun (經書正文, the Compilation of Four Books and Three Canons of Confucianism) and Gyemongjipjeon (啓蒙集箋, the Compilation of Zhu Xi’s Works) using these characters while keeping them in Ungak (芸閣, the storage at the Royal Publication Ministry). In the same year he also ordered the former governor of Pyeongan province, Seo Myeongeung, to initiate casting 150,000 characters in Giyeong (箕營) based on Gabinja, known as Jeongyuja (丁酉字).” This confirms the facts surrounding the founding of Gabinja, used the most during the Joseon Dynasty, and the later re-cast Imjinja and Jeongyuja.

The research on the sand metal movable typecasting technique is based on these original documents and is being refined as more records are confirmed. Based on up-to-date research and experiments, the process can be recreated and summarized as following:

Once the mold is completely broken the bronze tree branch base and character pieces will appear.
Flip the bottom mold and arrange the movable type matrix on the bottom inside surface. Check the passage way of the liquefied iron and the size of the characters at this time, and make sure the letter surface faces upward.
Use a sand sieve to evenly cover the bottom area surrounding the movable type matrix.
Fill up the mold with sand and knock on the inside of the mold slightly or press down so the movable type matrix is fixed.
Fill the mold with sand up to the top and make it even using a line gauge.
Fill the bottom mold completely with sand and then flip it.
Lock the top mold with the bottom mold, snap the connective piece attached to the girth, and fill them with sand using the sand sieve.
When the top mold is filled about halfway with sand, knock on it with a pounder to pack the sand hard and evenly. Once the sand fills the entire mold, level it with a line gauge.
Look at the flip side of the master-letters in the background and determine the direction, length and thickness of the passage way of liquefied iron and its branches. Paint the approximate passageway and its branches with a brush dipped in water. Dig the sand out according to the water marks using an engraver.
Poke the back side of the master-letters with an awl type of instrument while stroking it lightly and remove it vertically.
Apply heat to the passageway to reduce moisture and combine the top and bottom plates; fix them by connecting the hooks on the girth and position the prepared mold at an angle so the liquefied iron can flow easily.
During the above process, melt the optimum amount and ideal alloy of copper, tin and others in a crucible to get it ready to be poured into the mold. The optimal temperature for the liquid alloy is about 1,200 degrees Celsius, and ingredients like lead, zinc and sulfur are supposed to be added five minutes before the liquid is poured.
Pour in the liquefied iron and wait until it cools down. Separate the mold and rub the iron branch section with an iron brush, or a tough brush of any kind, to make sure it is molded. Cut the type pieces away from the iron branch using an iron saw and complete the process by trimming the whole thing including the letter surface and the letter pole.

The Sand Typecasting Process

Footnote

↑ 成俔, 慵齋叢話. 卷7. ‘鑄字’條. 太宗於永樂元年謂左右曰凡爲治必須博觀典籍...大抵鑄字之法先用黃楊木刻諸字以海浦軟泥平鋪印板印着木刻字於泥中則所印處凹而成字於是合兩印板鎔銅從一穴瀉下流液分入凹處一一成字遂刻剔重複而整之...
↑ 成俔, 慵齋叢話. 卷7. ‘鑄字’條刻木者曰刻字匠鑄成者曰鑄匠遂分諸字貯於藏櫝其守者曰守藏年少公奴爲之其書草唱准者曰唱准皆解文者爲之守藏列字於書草上移之於板曰上板用竹木破紙塡空而堅緻之使不搖動者曰均字匠受而印之者曰印出匠其監印官則校書館員爲之監校官則別命文臣爲之...
↑ 正祖實錄第4卷. 正祖元年 8月丙申條. 鑄字成鑄字成世宗甲寅命金墩等以孝順事實. 爲善陰隲字範銅爲字凡二十餘萬字俗稱衛夫人字是也至宣廟朝重修其字上在春邸命宮僚校正甲寅字鑄十五萬字藏于芸閣印行經書正文. 啓蒙集箋是爲壬辰字是年命前平安監司徐命膺開鑄箕營以甲寅字爲本加鑄十萬字以進是爲丁酉字至是敎曰重臣前後勤勞甚著從此可以壽傳我英廟之志事於幾千百載豈是等閒勞役之比況有已例者乎且此重臣卽予春宮舊賓今又爲同休戚之人而至於要地予不强勉其宜置之閒局前監司徐命膺特陞判中樞階仍復除奎章閣提學.