靑銅遺物의 鑄造와 復原技術 硏究

다국어 초록 (Multilingual Abstract)

This research would aim to define casting and restoration technology of bronze artifacts. In order to achieve this, I have tried to determine the mechanism of casting techniques includes material, cast and alloy that were used for bronze artifacts. On a basis of mechanism, I will then represent the restoration technology through a restoration casting experiment and further establish a standard of material, casting and restoration techniques that has been utilized by scientific analyses on restoring bronze artifacts.

In the first chapter, I examined the earlier studies on bronze mirror in the Bronze Age, bronze bell in the unified Silla period and metal type in Goryeo & Joseon Dynasty and set up a scope of research focusing a controversy in the academia.
The controversy commonly focuses on casting method. When it comes to bronze mirror with fine linear designs,various casting methods such as stone casting, beeswax casting(Lost-wax casting), sand mold casting and porcelain clay casting method has been suggested. And beeswax casting(Lost-wax casting) and sand mold casting method for bronze bell and metal type has become one of the major issues of the discussion in particular.
In the second chapter, I looked at the casting techniques depends on materials and casting techniques that have been written in the literature for the sake of understanding the traditional bronze casting method that certainly is a precedent study for the investigation of bronze artifacts' restoration techniques.
First of all, The casting techniques have been seen in the literatures are beeswax casting(Lost-wax casting), sand mold casting and porcelain casting method. Especially, the records of beeswax casting(Lost-wax casting) method are found in the technology industry book(Cheongong
Gaemul) written by Song Eung-Seong in the Ming Dynasty. It has been playing a critical role in restoring the bronze artifacts.
In addition, the sand mold casting method is found in Yongjae Chonghwa, Cheongong Gaemul and the『The Korean Review』 which contains metal type casting of Joseon Dynasty, iron bell & coin casting and coin casting of the Joseon Dynasty in each. They help us to figure out the fact that sand mold casting was used for metal type in Joseon Dynasty and they used same sand mold casting method to iron bell and coin as we do now.
In terms of casting technique depends on materials, I dealt with beeswax casting(Lost-wax casting), sand mold casting, porcelain casting, stone casting and metal casting method that can be observed and predicted in the excavated artifacts as well as the traditional casting method that has been transmitted.
In the third chapter, I have tried to suggest restoration technology of bronze artifacts by looking at the restoration experiment on metal type, bronze mirror with fine linear designs, bronze bell using beeswax casting(Lost-wax casting) and sand mold casting based on bronze casting
technology according to materials and literatures in the preceding paragraph.
Above all, The relics that restoration technology has applied is the bronze mirror with fine linear designs which was excavated at Nonsan(National treasure No.141) and also the Hwasun Daegok-Ri(National treasure No.143). As for the cast that was used for beeswax casting(Lost-wax casting), clay mixed with soft stone, burnt ocher and sand were utilized at a rate of 60, 30 and 10 percentages in each. To elevate the permeability, I differed the inside and outside by completing the side that meets the beeswax with finer grain along with by finishing the upper side with rough particle and the surface with coarse grained silty soil.
In the aspect of alloy components for restoration, I set up components with a rate of Cu 71%, Sn 23%, Pb 6% and Cu 62%, Sn 32%, Pb 6% for the other based on bronze mirror with fine linear designs excavated in Nonsan and also the Wonbuk-Ri, Nonsan. In order to look at some of the changes made in main component before and after the casting, I made a comparison by casting with a range of principal component value with Cu 80%, Sn 14%, Pb 6% and smelted from a copper and tin to lead.
The important feature of this study of bronze mirror with fine linear designs is it proposes a new theory by making a beeswax mirror without engraving patterns in the mirror at first hand but instead they made a beeswax mirror cast separately by engraving patterns in the talcum which is known as a stone. Moreover, it suggests an opinion that it is quite probable that it's a beeswax casting on a basis of result of study on sand mold casting that has been suggested by academia recently. The basis of this is that the defect of casting method and patterns along with the casting soil with red color has been observed in the restoration process by beeswax casting.
In sequence, the restoration technology used for restoring the bronze bell is targeting Seonlimwon bell, Buddhist temple bell. The materials for beeswax casting(Lost-wax casting) are mudstone, burnt ochre, sand and beeswax which are used after the pulverization. When making a beeswax, I divided the proportion of beeswax and resin into two. I used 7:3 proportion when making a beeswax and 5:5 rate when attaching beeswax after pouring the pieces from pelite cast to beeswax. Then I set up with
a rate of Cu 83~35%, Sn 15~17% as a basic alloy components for restoration. I believe that by defining a mechanism of beeswax casting techniques for bronze bell It enables us to suggest a methodical theory to the academia that is involved and contribute to restoration of bronze bell in the unified Shilla in the near future.
Lastly, The relics used for restoring metal type are Jikji of beeswax casting in Goryeo Dinasty, and sand mold casting in Kanin-Ja of six types(2007), Gyechuck-Ja & Byeongjin-Ja(2008) in the earlier period of Joseon Dynasty and Jeongli-Ja(2009) in the latter period of Joseon Dynasty.
The materials used for beeswax are clay mixed with soft stones which covers between the beeswax, pelite, sand and red clay to name a few. In order to adjust the hardness of beeswax it is suitable to mix beeswax with beef tallow in a 2:8, beeswax with resin in a 6:4 and beeswax with lard in a 7:3.
The materials used for sand mold casting are composed of original mold plate frame and molding sand. The original mold plate frame is divided into wood and metal depending on materials. As for the molding sand, I used sand of Jeonbuk Iri region with a pale yellow color and utilized finer grain by sifting flour.
If we look at the alloy components that are used for restoration, Goryeo Jik-Ji restored by beeswax casting(Lost-wax casting) is based on the rate of Cu 80%, Sn 20% and the Kanin-Ja & master alloly of six types is based on the rate of Cu 80%, Sn 10%, Pb 10% which is the same rate used for Limjin-Ja. In view of the decrease in the components rate, I set up with a rate of Cu 72.8%, Sn 13.6%, Pb 13.6% by adding 5% of tin and lead in it.
As for the restoration of alloy and Gyechuk-Ja in the earlier period of the Joseon Dynasty, on a basis of the rate of Cu 86.7%, Sn 9.7%, Pb 2.3%, I set up with a rate of Cu 79%, Sn 14%, Pb 7% by adding 5% of tin and lead in it. And I cast a Byengjin-Ja with a rate of Pb 80% and Cu 20%.
On the restoration of metal type of latter period Joseon dynasty, it is based on Jeongli-Ja's average value of Cu 78.2%, Sn 10.8% and Pb 6.3% and in actual restoration, I set up with a rate of Cu 75%, Sn 14% and Pb 11% by adding 5% of Sn and Pb.
The remarkable point of this restoration experiment on metal type is that this study is focused on cast materials, elaboration and less amount of type casting in contradistinction to beeswax usage which have long argued in academia. Fist of all, mixed soil was used for casting materials with a rate of 65% of clay mixed with soft stone and 35% of red clay. Clay mixed with soft stone is regarded as the most appropriate material as it has less defects and has improved on its cast success rate up to 95%.
In order to resolve the problem of less amount of type casting in contradistinction to beeswax usage & elaboration, casting method in high volume has been applied which enables to cast the metal type from 10~15 to 80~100 at a time. The success rate of metal typecasting by using burying method in a mold which has a high volume production that has achieved a great success in its efficiency of casting up to a rate of 99%.

Chapter four covers a scientific analysis on restoring artifacts. In order to define the characteristic of materials that were used for the cast in beeswax casting(Lost-wax casting), I analyzed them through XRD, stereoscopic microscopes, SEM, TGA-DTA soon after making beeswax cast by mixing clay with soft stone with red clay. As a result, at a cast without firing quart, feldspar, mica and chlorite which is similar to raw material were detected. In contrast, at a cast with firing, chlorite wasn't detected and it had fired at a 850 degree. As a result of investigating the micro structure of each cast using stereoscopic microscope, unlike unfired cast which has simplified substrate, At a fired cast crack microstructure was identified at a place where the water of crystallization was flowing out in order to keep permeability.

After restoring and manufacturing by beeswax casting(Lost-wax casting) and sand mold casting that targeting restored bronze artifacts excavated at Nonsan and Hwasun Daegok-Ri and by conducting principal component analysis, micro structure analysis, X-rays, SEM and EDS analysis I analogize of the manufacturing process through a comparative analysis of bronze mirror made by beeswax casting(Lost-wax casting) method and sand mold casting method.
Through an analysis which has done to observe the inside of and micro structure of restored bronze mirror, I discovered that the bronze mirror made by beeswax casting (Lost-wax casting)method has irregular thickness and casting hole has found in the inside of the mirror. Besides on account of cooling velocity dendritic structure has grown with a coarse texture. In contrast, bronze mirror made by sand mold casting method, has a neat appearance and has an excellent quality in terms of thickness and patterns.
If we look at the component composition of bronze mirror before and after the casting, we will soon figure out that in a range of 80% of copper, copper component had increased. On the other hand, in a range of 70% of copper it had decreased. This can be observed when the alloy isn't mixed evenly or when a part where has a generous portion of lead segregation and tin had selected. The Pb segregation which is identified through an EDS analysis has a feature which makes the fluidity better and helps to make minute patterns.

In sequence, for the restoring of Seonlimwon bell, the same materials were used in beeswax casting(Lost-wax casting) two times(2005, 2012). Metallurgical analysis was conducted targeting specimen that has collected during the second restoration experiment. The result of examination of chemical components of Japan and Europe on restoring Seonlimwon bell is as follows.
Firstly, as for the Seonlimwon bell restoration bronze has been utilized(Cu 83%, Sn 17wt%) It composed with two different structures. One is the micro structure has low contents of its tin component,α-Cu(Tin Solubility 0~9.1at%). The other is the place where Cu41(Sn,Ni)11 and δ figure is scattered in the matrix with its high contents of tin.
Secondly, the observation using a scanning electron microscope shows a general knowledge of chemical distribution of its composition as it glows brightly where the tin contents is distributed broadly but appear dark where there is low tin contents in the matrix.
Thirdly, as a result of analysis of chemical composition of bronze, wavelength dispersed type-X has higher accuracy than energy dispersed type-X.
Fourthly, the chemical component of Shilla's bell is superior to Japan's bell.
Lastly, the scientific analysis on restoring metal type of Joseon Dynasty conducted three times on Gabin-Ja of six types in 2007, Gyechuk-Ja & Byeongjin-Ja of the early days of Joseon dynasty in 2008 and Jeongli-Ja of latter period of Joseon dynasty.
At first, for the metal type restoration, the contents of copper have increased at a percentage of 1.7 and 4.8 and it can be easily shown in diverse steps of casting. In other words, 77.1% of master alloy in the first step of casting, 78.8% of metal type which is the same line of Gabin-Ja has observed in the second step and 83.6% of metal type using branch shaped molten metal in the third step has observed.
This phenomenon is formed when before copper smelting, the tin and lead had evaporated and as a benefit in return the contents of copper has increased. Especially, the changes of copper component rate in Korean metal type which made by smelting branch shaped molten metal helps to investigate the reason why Limjin-Ja is owned by National Museuem of Korea has a large deviation in comparison with the Korean metal type.

The conclusion of scientific analysis has done in 2008 is as follows.
First, it is most clear on its concentration and print at the rate of 80 in the lead and 20% in copper when restoring Byeongjin-Ja.
Second, as a result of component composition in restoring metal type of Gyechuk-Ja primarily. It has shown a range of Cu 85.81~87.63%, Sn 9.27~10.51%, Pb 3.05~3.19% and this is the same component composition of Ulhae-Ja is owned by National Museuem of Korea.
Third, as a result of observation of specimen restored of Gyechuk-Ja. The dendrite which is the typical type main structure of bronze has well developed and the eutectoid structure α+δ is observed around dendritic structure α figure and lead segregation are scattered inside of the structure. The conclusion of scientific analysis on restoring metal type in 2009 as follows.
First, Comparing the components of master alloy before the casting(Cu 75%, Sn 14%, Pb 11%) the copper contents has increased at a rate of 2% but tin and lead contents have decreased at a rate of 1% and 2% in each.
It is because the tin and lead has evaporated when casting master alloy.
Second, In case of Pung-Gojib metal type which is restored Jeongli-Ja using master alloy(Primary),It has components ranges Cu 82.3~82.4%, Sn 13.0~14.7%, Pb 3.3~3.4% as a result of wet-analysis(ICP-ACE) and it's worthy noticing that it's similar to Jengli-Ja's principal components of average value of Cu 82.1%, Sn 11.3%, Pb 6.6%.
Third, the specimen by measuring by means of Fluorescence analysis of X rays (XRF) consists of 3types which is the master alloy for restored Jeongli-Ja, Jeongli-Ja that is initially cast using master alloy and Jeongli-Ja secondarily cast by smelting branch shaped molten metal that remains in its initial cast. Among these, alloy component ratio shows an approximate ratio as Jeongli-Ja alloy component ratio has measured by ICP-AES analysis.
Fourth, as a result of XRF conducted to metal type is owned by Wonkwang university museum, It is composed with Fe 39~71%, Cu 6.9~36%, As(Arsenic) 16.9~22.4% and yet it is an unusual example as it contains more that 16% of arsenic and it is alloyed iron with nonferrous copper. The reason why arsenic is contained is because to strengthen the structure by keeping tin from acting as a solid solution with the iron.
Fifth, When we look at the principal components of brass type is owned by Wonkwang university it consists of Cu 76.20~77.79%, Zn 15.20~15.72%, Pb 2.72~3.90% and Sn 2.70~2.85%. The component ratio of copper 76~77% is the phenomenon of alloy ratio when casting metal type since Ulhae-Ja in Joseon Dynasty but this is the first case to be reported that it contains more that 15% of zinc.
Sixth, As a result of observing micro structure of specimen restored Jeongli-Ja, metal type of Joseon Dynasty, the dendrite structure of typical bronze cast structure has well developed and branch shaped molten metal α+δ figure has observed around the dendritic structure αfigure and lead segregation has scattered in inside of structure.

Key Words:
Bronze artifacts, Casting technology, Restoration technology, Cast, Alloy, Stone casting, Beeswax casting(Lost-wax casting), Sand mold casting and porcelain clay casting method, Bronze mirror with fine linear designs, Bronze bell, Metal type, scientific analyses, Component analysis, Micro structure, XRD, Stereoscopic microscopes, SEM, TGA-DTA, X-rays, EDS, Wavelength dispersed type-X, Energy dispersed type-X, Wetanalysis(ICP-ACE), Fluorescence analysis of X rays.

국문 초록 (Abstract)

이 연구는 靑銅 遺物에 대한 鑄造와 復原技術 규명에 그 목적을 두고 있다.
이를 위해 청동 유물에 사용된 소재, 거푸집, 합금 등 주조기술에 대한 메커니즘을 밝혀, 이를 기초로 한 복원 주조실험을 통하여 유물의 복원기술을 제시하고,나아가 복원된 청동유물에 대한 과학 분석을 통하여 청동유물 제작에 사용된 소재와 주조기술, 그리고 복원기술에 대한 기준을 마련하고자 하였다.
먼저, Ⅰ장에서는 청동기시대 청동거울, 통일신라 청동종, 고려와 조선의 금속활자 등에 대한 지금까지의 연구 결과를 살펴보고 그와 관련된 학계의 논쟁을 중심으로 연구의 범위를 설정하였다.
논쟁은 공통적으로 청동유물의 주조방법에 집중되어 있는데, 청동잔무늬거울의 경우에는 石製鑄造法, 蜜蠟鑄造法, 鑄物砂鑄造法, 陶土鑄造法 등 다양한 주조방법이 제시되고 있으며, 청동종과 금속활자는 蜜蠟鑄造法과 鑄物砂鑄造法이 논의의 주요 쟁점이 되고 있다.
Ⅱ장에서는 쟁점이 되고 있는 청동유물 주조기술 규명의 선행 과제인 전통 청동주조법 이해를 위해, 문헌에 보이는 주조기술과 재료에 따른 주조기술에 대해살펴보았다.
먼저, 문헌에 보이는 주조기술로는 밀랍주조법, 주물사주조법, 도토주조법 등이 있는데, 그 중 밀랍주조법에 대한 기록은 중국 명나라 송응성이 지은 『天工開物』에서 찾아 볼 수 있으며, 그 내용은 밀랍주조법으로 청동유물을 복원하는데 중요한 역할을 하고 있다. 또한 주물사주조법은 조선시대 금속활자주조법이 담긴 『慵齋叢話』, 철종과 동전주조법이 있는 『天工開物』, 조선시대 동전주조법이 담긴『The Korean Review』 등에서 찾아 볼 수 있는데, 이를 통해 조선시대 금속활자에 주물사[砂型]주조법이 사용되었고, 문헌에서의 철종주조법과 동전주조법이 현재 우리가 사용하고 있는 주물사주조법과 유사한 방법임을 알 수 있다.
재료에 따른 주조기술에서는 전통주조법으로 이어져 오거나 출토되는 유물을 통해 관찰 또는 예측해 볼 수 있는 밀랍주조법, 주물사주조법, 도토주조법, 석제주조법, 금속주조법에 대해 다루었다.
Ⅲ장에서는 앞장에서 다룬 문헌과 재료에 따른 청동주조기술을 바탕으로 밀랍주조법과 주물사주조법을 적용한 청동잔무늬거울, 청동종, 금속활자에 대한 복원주조실험을 살펴봄으로써 청동유물의 복원기술을 제시하고자 하였다.
먼저 청동잔무늬거울의 복원에 적용된 주조기술의 대상 유물은 논산 출토 잔무늬거울(국보 141호)과 화순 대곡리 출토 잔무늬거울(국보 143호)로, 밀랍주조에 사용된 거푸집에는 석비레, 구운 황토, 모래가 각각 60%, 30%, 10% 정도 사용되었고, 통기성을 높이기 위해 안팎을 달리하였는데, 밀랍과 맞닿는 면은 고운입자, 그 위는 거친 입자, 표면은 좀 더 굵은 입자인 마사토를 섞어 마무리했다.
복원에 사용된 합금 성분은, 논산 원북리 출토 청동잔무늬거울과 논산 출토 청동잔무늬거울을 기준으로 하여 Cu 71%, Sn 23%, Pb 6%와 Cu 62%, Sn32%, Pb 6%로 설정하였으며, 주조 전의 주성분과 주조 후의 주성분 변화를 살펴보기 위하여, 청동활자의 주성분 값인 Cu 80%, Sn 14%, Pb 6%로 주조한 뒤 각기 비교하여 보았다. 금속을 녹이는 순서는 동, 주석, 납의 순으로 하였다.
이번 청동잔무늬거울 연구에서의 특징은, 밀랍에 직접 문양을 새겨 밀랍거울을 만들지 않고, 석재인 활석에 문양을 새겨 별도의 밀랍거울 ‘거푸집’을 제작하여 사용했다는 이론을 새롭게 제시한 것과, 최근 학계에서 제시한 砂型주조법에 대해 연구 결과를 바탕으로 밀랍주조일 가능성이 높다는 의견을 제시할 수 있게 되었다는 것인데, 그 근거는 청동잔무늬거울에서 나타는 주조결함, 문양의 결함,황토색 빛깔의 주물토 등이 밀랍주조를 통한 복원에서도 관찰된다는 것이다.
다음으로 통일신라 청동종 복원에 적용된 주조기술은 선림원종을 대상으로 하였는데, 밀랍주조법에 사용된 거푸집의 소재는 분쇄한 뒤 사용하는 泥岩(뻘돌)과 구운 황토·모래, 그리고 蜜蠟이다. 밀랍 제작 시 밀랍과 송진 비율은 2가지로 구분하였는데, 7:3은 밀랍의 겉 거푸집을 만들 때, 5:5는 이암거푸집에서 밀랍으로 조각을 부어낸 뒤, 거푸집에 붙일 때 사용하였다. 복원에 사용된 합금 성분은 Cu83~85%, Sn 15~17%를 기본 조성으로 하였다. 이번 연구를 통해 청동종 밀랍주조기술의 메커니즘을 규명함으로써 체계적인 이론을 학계에 제시하게 되었을뿐 아니라 향후 통일신라 청동종 복원에 기여할 것으로 판단된다.
마지막으로 금속활자 복원에 적용된 주조기술의 대상유물은 밀랍주조법의 고려시대 직지, 주물사주조법의 조선시대 6종의 甲寅字(2007년), 조선전기 금속활자인 癸丑字와 丙辰字(2008년), 조선후기 금속활자인 整理字(2009년)이다.
밀랍주조법에 사용된 소재는 밀랍과 밀랍을 감싸는 석비레, 이암토, 모래, 황토 등이며, 밀랍은 굳기를 조절하기 위해 밀랍과 쇠기름을 2:8, 밀랍과 송진을6:4, 밀랍과 돼지기름을 7:3 비율로 배합하는 것이 적당하다.
주물사주조법에 사용되는 거푸집의 소재는 본기(本器)틀과 주물사로 구성된다.본기틀은 주물사를 담는 바깥 틀로 재질에 따라 목틀과 쇠틀이 사용되며, 주물사는 옅은 황색의 전북 이리사를 사용했고, 체로 쳐 입자가 고운 것을 사용하였다.
복원에 사용된 합금 성분비를 살펴보면, 밀랍주조법으로 복원 실험한 고려 직지는 Cu 80%, Sn 20%, 주물사주조법으로 복원 실험한 조선시대 금속활자 중2007년도의 6종의 모합금과 甲寅字에는 오주갑인자인 壬辰字의 성분비인 Cu80%, Sn 10%, Pb 10%를 근거로 하였으며, 실제 복원에는 합금 시 주석과 납이기화되어 날아가 성분비율이 줄어드는 것을 감안하여 주석과 납을 각각 5% 더하여 구리 72.8%, 주석 13.6%, 납 13.6%로 설정하였다.
2008년도의 조선전기 금속활자의 모합금과 癸丑字 복원에는 乙亥字 성분비의평균값 Cu 86.7%, Sn 9.7%, Pb 2.3%를 합금 기준으로 하여, 실제 복원에는Sn, Pb를 5%씩 더 첨가하여 구리 79%, 주석 14%, 납 7%로 설정하였다. 또한납활자인 丙辰字에 대한 합금비율은 납 80%, 구리 20%로 주조하였다.
2009년도의 조선후기 금속활자 복원의 합금기준은 국립중앙박물관 소장 整理字의 성분비 평균값 Cu 78.2%, Sn 10.8%, Pb 6.3%를 근거로 하였으며, 실제복원에는 Sn, Pb를 5% 더 첨가하여 구리 75%, 주석 14%, 납 11%로 하였다.
이번 금속활자 복원 실험에서의 특징은 학계의 논쟁이 되고 있는 밀랍주조법에 사용된 거푸집 재료와, 공력과 밀랍사용 대비 적은 수량의 활자주조에 대해주안점을 두고 연구가 진행된 점으로, 먼저 주형 재료는 천연소재인 석비레65%, 황토 35% 비율로 섞은 혼합토를 사용하였는데, 석비레는 활자의 주조 결함이 적고 鑄成率이 95% 이상으로 개선되어 가장 적합한 재료로 판단되었다.
공력과 밀랍사용 대비 적은 수량의 활자주조에 대한 문제점을 해결하기 위해서는 한 번에 주조 할 수 있는 활자 수량을 10~15개 정도에서 80~100여개 정도로 효율성을 높인 多量주조법을 적용하였는데, 多量주조법에 의한 틀안 매몰방식은 활자 주조 성공률이 99%에 이를 정도로 주조 효율성이 상당히 높았다.
Ⅳ장에서는 復原遺物의 科學分析을 다루었는데, 그에 앞서 밀랍주조법에 사용되는 거푸집 재료의 특성을 밝혀보기 위해서 석비레, 황토 등을 섞어 밀랍 거푸집을 제작 후 이들의 재료학적 특성을 XRD, 실체현미경, SEM, TGA-DTA 등을이용해 분석하였다. 그 결과 燒成하지 않은 거푸집에서는 原材e와 유사한 석영,장석, 운모, 녹니석 등이 검출되었고, 소성 거푸집에서는 녹니석이 불검출 되었으며, 검출된 성분을 통해 약 850℃ 내외의 온도에서 소성되었음을 확인하였다.
그리고 실체현미경과 SEM 등을 이용하여 각 거푸집의 미세조직을 관찰한 결과 기질이 치밀하지 못한 미 소성 거푸집과 달리, 소성된 거푸집의 경우는 결정수가 빠져나간 자리에 무수히 많은 미세한 틈들이 존재함을 알 수 있었는데, 이러한 틈들을 통하여 통기성을 유지할 수 있는 것으로 보인다.
과학 분석 대상인 복원된 청동유물 중 먼저, 논산 출토 잔무늬거울과 화순 대곡리 출토 잔무늬거울에 대해서는 밀랍주조법과 주물사주조법으로 복원 · 제작한뒤, 주성분분석, 미세조직, X-ray 촬영, SEM, EDS 분석을 실시하고 밀랍주조법과 주물사주조법으로 주조한 청동거울과 비교 · 분석함으로써 그 결과를 토대로제작방법을 유추해보았다.
복원한 청동거울의 내부와 미세조직 관찰을 통해, 밀랍주조법으로 주조한 청동거울들은 두께가 일정하지 않고 내부에 주물공이 확인되었으며, 탕구의 냉각속도가 테두리보다 늦어 수지상 조직이 조대하게 성장한 것을 알 수 있었다. 반면주물사주조법으로 주조한 것은 밀랍주조법에 비해 외형도 깔끔하며 두께, 문양등이 우수하게 주조됨을 확인할 수 있었다.
복원된 청동잔무늬거울의 주조 전·후의 합금 성분조성을 보면, 구리 80%대에서는 구리 조성비가 증가되는 반면, 구리 70%대에서는 오히려 감소하는 것이 관찰되었는데, 이는 주조 시 합금이 고르게 섞이지 않았을 경우와 성분 분석 시 납편석 또는 주석이 많은 부분이 선택됐을 경우에 나타날 수 있을 것이다. 또한EDS 분석을 통해 확인된 Pb 편석물은 주조 시 유동성을 좋게 하는 성질을 지고 있으므로 청동거울의 미세 문양을 제작하는데 도움이 되었을 것으로 보인다.
다음으로 통일신라 청동종인 선림원종 복원은 2005년과 2012년 2차례에 걸쳐 밀랍주조법으로 이루어졌으며 동일한 소재가 사용되었다. 금속학적 분석은 2차 복원 실험에 채취한 시료를 대상으로 하였으며, 복원한 선림원종에 대한 분석및 일본, 유럽 종들과의 화학조성 검토를 통하여 얻은 결과는 다음과 같다.
첫째, 선림원종 복원에는 청동(Cu 83%, Sn 17wt%)이 사용되었으며, 미세조직은 주석 함량이 낮은 α-Cu (주석고용도0~9.1at%) 기지조직에 주석 함량이높은 Cu41(Sn, Ni)11 δ상이 분산되어 있는 2상 구조로 이루어져 있었다.
둘째, 주사전자현미경으로 관찰한 미세조직은 주석 함량이 높은 부위는 밝게빛나고, 주석 함량이 낮은 기지조직 부위는 어둡게 나타나 조직사진의 밝기로부터 대략적인 화학조성의 분포를 알 수 있었다.
셋째, 복원에 사용된 청동의 화학성분을 분석한 결과 파장 분산형 X-선 분광기의 정확도가 에너지 분산형 X-선 분광기보다 높게 나타났다.
넷째, 신라종의 화학조성이 일본종의 화학조성보다 우수하게 나타났다.
마지막으로, 복원된 조선시대 금속활자의 과학 분석은 2007년의 조선시대 6종의 甲寅字, 2008년의 조선전기 금속활자인 癸丑字와 丙辰字, 2009년의 조선후기 금속활자인 整理字 등 3번에 걸쳐 이루어졌다.
먼저, 2007년 금속활자 복원에서는 구리함량이 주조 1단계인 모합금이77.1%, 주조 2단계인 갑인자계열 금속활자가 78.8%, 주조 3단계인 가지쇠 이용금속활자는 83.6%로 비율이 각각 1.7%, 4.8%로 늘어났음을 알 수 있는데, 이러한 현상은 용융할 때 구리가 녹기 전에 주석과 납 등이 일부 기화되어 날아감에 따라 반대급부로 구리의 함량이 늘어나 생긴 것으로, 특히 가지쇠를 녹여 만든한글금속활자에서 보이는 구리의 성분비 변화는 국립중앙박물관 소장 임진자와한글활자에서 보이는 큰 편차의 성분비에 대한 원인 규명에 도움이 될 것으로 보인다.
2008년도에 복원된 금속활자에 대한 과학 분석 결론은 다음과 같다.
첫째, 병진자 복원 시 납과 구리의 비율이 80:20일 때 활자체와 농도가 가장선명하였다.
둘째, 계축자를 1차로 복원한 활자에 대한 성분조성 결과 Cu 85.81~87.63%,Sn 9.27~10.51%, Pb 3.05~3.19%의 범위를 보였는데, 이것은 국립중앙박물관에서 소장하고 있는 을해자의 평균조성과도 거의 일치하는 결과이다.
셋째, 계축자를 복원한 시편의 미세조직 관찰 결과, 청동의 전형적인 주조 조직인 수지상(dendrite) 조직이 잘 발달해 있으며, 나뭇가지 모양의 수지상인 α상주위로 공석상인 (α+δ)상이 관찰되며, 납 편석물들이 조직 내에 산재해 있었다.
2009년도에 복원된 금속활자에 대한 과학 분석 결론은 다음과 같다.
첫째, 모합금 성분비는 주조 전 기준 합금(구리75%, 주석14%, 납11%)과 비교하였을 때 구리는 2% 증가, 주석과 납은 각각 1%, 2% 정도 감소되었는데, 이는 모합금 주조 시 주석과 납이 액체 상태에서 기화되어 성분이 줄어든 것이다.
둘째, 모합금을 이용하여 주조한 복원(1차) 정리자인 풍고집 활자에 대한 습식분석(ICP-ACE)으로 성분조성을 살펴본 결과, 1차로 복원된 정리자의 성분조성은 구리 82.3~83.4%, 주석 13.0~14.7%, 납 3.3~3.4%의 범위이며, 이러한 성분조성은 국립중앙박물관의 정리자 주성분의 합금비 평균값인 구리 82.1%. 주석11.3%, 납 6.6%와 비교적 근사한 값을 보이고 있어 주목된다.
셋째, X-선 형광분석(XRF) 방법으로 측정한 시료는 정리자 복원용 모합금,모합금을 이용하여 1차로 주조(주조 2단계)한 정리자, 1차 주조 시 남은 가지쇠를 녹여 2차 주조한 정리자 등 3종인데, 이 중 모합금의 조성비는 ICP-AES분석으로 계측된 정리자 모합금의 평균 조성비와 서로 근사한 수치를 보이고 있다.
넷째, 원광대 박물관 소장 철활자에 대한 X-선 형광분석(XRF) 실시 결과, 철39~71%, 구리 6.9~36%, 비소(As) 16.9~22.4%로 조성되었는데, 철과 비철금속인 구리가 함께 합금되었다는 점이 특이하며, 또한 비소가 16%이상 함유된 것은흔치 않은 사례이다. 비소가 함유된 것은 철에 대해 주석이 고용체로서의 역할을하지 못해 조직을 단단히 하기 위한 역할로 사용된 것으로 보인다.
다섯째, 원광대 소장 황동활자의 주성분을 보면 구리76.20~77.79%, 아연15.20~15.72%, 납 2.72~3.90%, 주석 2.70~2.85%로 계측되었는데, 구리76~77%의 조성비는 조선시대 을해자 이후에 금속활자 주조 시 보이는 합금비율현상이지만, 아연이 15%이상 함유된 경우는 처음 보고되는 사례라 하겠다.
여섯째, 조선 시대 금속활자인 정리자를 복원한 시편의 미세조직을 관찰한 결과 청동의 전형적인 주조 조직인 수지상(dendrite) 조직이 잘 발달해 있으며, 가지상 모양의 수지상인 α상 주위로 공석상인 (α+δ)상이 관찰되고, 납 편석물들이 조직 내에 산재해 있음을 알 수 있다.
주제어 : 靑銅遺物, 鑄造, 復原技術, 거푸집, 합금, 石製鑄造法, 蜜蠟鑄造法, 鑄物砂鑄造法, 陶土鑄造法, 청동잔무늬거울, 청동종, 금속활자, 科學分析, 성분분석, 미세조직, XRD, 실체현미경, SEM, TGA-DTA , X-ray 촬영,EDS, 파장 분산형 X-선 분광기, 에너지 분산형 X-선 분광기, 습식분석ICP-ACE), X-선 형광분석(XRF)

목차 (Table of Contents)

• Ⅰ. 序 論······························································································ 1
• 1. 硏究目的 및 硏究史······································································ 1
• 2. 硏究範圍 및 限界·········································································· 9
• Ⅱ. 靑銅遺物의 鑄造技術································································ 11
• 1. 文獻에 보이는 鑄造技術···························································· 13
• 1) 蜜蠟 鑄造技術············································································· 13
• 2) 鑄物砂 鑄造技術········································································· 15
• 3) 陶土 鑄造技術············································································· 30
• 2. 材料에 따른 鑄造技術································································ 31
• 1) 蜜蠟 鑄造技術············································································· 31
• 2) 鑄物砂 鑄造技術········································································· 33
• 3) 石製 鑄造技術············································································· 34
• 4) 陶土 鑄造技術············································································· 38
• 5) 金屬 鑄造技術············································································· 40
• Ⅲ. 靑銅遺物 復原技術···································································· 41
• 1. 靑銅잔무늬거울 復原技術·························································· 41
• 1) 蜜蠟鑄造法··················································································· 41
• 2) 鑄物砂鑄造法··············································································· 89
• 2. 靑銅鍾 復原技術········································································ 103
• 1) 蜜蠟鑄造法················································································· 103
• 2) 鑄物砂鑄造法············································································· 129
• 3. 金屬活字 復原技術···································································· 151
• 1) 蜜蠟鑄造法················································································· 151
• 2) 鑄物砂鑄造法············································································· 170
• Ⅳ. 復原遺物의 科學分析······························································ 213
• 1. 科學分析方法············································································· 213
• 2. 蜜蠟을 이용해 鑄造된 金屬活字와 거푸집의 材e學的 特性· 217
• 3. 復原 청동잔무늬거울 科學分析·············································· 234
• 4. 復原 靑銅鍾의 科學分析·························································· 243
• 5. 復原 朝鮮時代 甲寅字 金屬活字의 科學分析························ 260
• 6. 復原 朝鮮前期 金屬活字의 科學分析····································· 275
• 7. 復原 朝鮮後期 金屬活字의 科學分析····································· 308
• Ⅴ. 結論··························································································· 340
• 참 고 문 헌 ···················································································· 351
• Abstract ························································································· 369