• Journal of Conservation Science
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• v.27 no.4
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• pp.421-430
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• 2011

Thermal conditions in practice at the traditional bronze workshop of the Korean Folk Village in Yongin were examined along with the microstructures of some high tin bronze objects made there. Laboratory experiments approximating the conditions of the workshop were also carried out and the results were compared. The operating temperature of the workshop furnace was measured to range from $750^{\circ}C$ to $850^{\circ}C$ while the surface temperature of an object, upon its removal from the furnace for additional thermo-mechanical treatments, was generally in the range of $600^{\circ}C$ to $685^{\circ}C$. This variation in working temperatures was reflected in varying microstructures developed upon quenching. The products of the Folk Village were found to consist of microstructures where the ${\alpha}$ grains of the Cu-Sn system were distributed in the background of different phases including the ${\beta}$-martensite phase, retained ${\gamma}$ phase, ${\alpha}+{\delta}$ eutectoid or their mixtures. This variability, which is also identified in objects made in ancient times as well as in our laboratory experiments, suggests that the actual thermal conditions given during the quenching treatments are much more complicated than is inferred from the temperature measurements. This paper will present detailed accounts of the thermo-mechanical treatments as observed in the high tin bronze workshop of the Korean Folk Village and discuss the evolution of varying microstructures in terms of the substantial variability involved in the implementation of the traditional forged high tin bronze technology of Korea.

• Journal of Conservation Science
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• v.34 no.6
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• pp.493-502
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• 2018

Currently, the fabrication of a high-tin bronze spoon by traditional manufacturing techniques involves 10 steps in the bronze ware workshop. Hot forging has a major influence on manufacturing and involves two to three steps. The dendritic ${\alpha}$-phase in the microstructure of the high-tin bronze spoon is refined and finely dispersed through hot forging. In addition, twinning is observed in the ${\alpha}$-phase of the hammered part, and the ${\alpha}$-phase microstructure gradually transform from a polygon to a circular shape due to hammering. In this process, the adjacent ${\alpha}$-phases overlap with each other and remain combined after quenching. The microstructure with the overlapping is also observed in bronze artifacts, and this shows the correlation with technical system. The results of the experimental hot forging of Cu-22%Sn alloys show that the decrease in in the amount of the dendritic microstructure, which forms during casting, is in proportion to the number of processing steps and that the refined grain obtained by hammering contributes to the improvement in the strength of the material. From the hammering marks, which are observed on both the bronze artifact excavated from archaeological sites and on the high-tin bronze spoon produced in the traditional workshop, it is presumed that the knowledge regarding the unrecorded manufacturing system of bronze ware in ancient times has been passed down in a traditional way up to the system used currently.

• Journal of Conservation Science
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• v.28 no.4
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• pp.403-410
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• 2012

The brine treatment applied during the fabrication of forged high tin bronze objects is considered effective at the removal of surface oxide layers developed at elevated temperatures. There is not much information, however, available for the understanding of its exact effect and purpose. This work performed laboratory experiments to characterize the effect brine treatments produce on the surface of bronze objects during fabrication. Specimens were first made in the bronze shop of the Yongin folk village under varying conditions of brine treatments, and the results obtained were then used in the following laboratory experiments where the effect of brine treatments were investigated in terms of brine concentrations, alloy compositions and thermo-mechanical treatments. The results show that oxide layers generated at high temperature are easily removed by the brine treatment. It was found that the element, chlorine, played a key role in the removal of such oxide layers as opposed to the other constituent of the brine, sodium, makes no notable contribution. In bronze alloys containing 22% tin, this brine effect is obtained regardless of the application of forging as long as the brine concentration is over 0.5% based on weight. In alloys containing lead, however, no brine effect is observed due to the molten lead that emerges from inside the hot bronze specimen and forms a thin layer on its surface.

• Korean Journal of Metals and Materials
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• v.46 no.1
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• pp.26-32
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• 2008

Examination of two bronze vessels supposedly from the Koryo dynasty revealed that they consist of bowls and stands that are fixed together using rivet joints made of Cu-Ag alloys. The bowls and stands were forged out of unleaded bronze alloys of approximately 22 weight % Sn before being quenched from the ${\alpha}+{\beta}$ region of the Cu-Sn phase diagram. This specific alloy and the thermo-mechanical treatment constitute two key elements of the unique technical tradition called Bangcha (방짜) that has long been established in Korea. The high Sn content ensures better casting and the thermal treatment causes the brittle ${\delta}$ phase to be avoided in forging as well as in services. The experiment on the laboratory Cu-Ag alloys of varying Ag contents suggested that the Cu-Ag system was the best choice of materials for the rivets at the time in view of their color, availability, ductility and low melting points.

• Korean Journal of Heritage: History & Science
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• v.54 no.2
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• pp.22-37
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• 2021

The wind chime is a longstanding Jangeomgu (majestic article) found in Korea, China, and Japan. However, basic research on wind chimes is currently inadequate as it is difficult to estimate the time of production, and there are few relics. Therefore, this research morphologically classifies the eight bronze wind chimes decorating the baldachin of the Stone Standing Maitreya Bodhisattva of Gwanchoksa Temple, Nonsan. Based on this, the manufacturing techniques and production period are scientifically demonstrated. The synthesis of the research results reveals that the structure and characteristics of the wind chimes of the Stone Standing Maitreya Bodhisattva of Gwanchoksa Temple, Nonsan differ depending on their location on the baldachin. The four large-sized wind chimes on the lower-baldachin were manufactured by casting a Cu-Sn-Pb alloy, and they are estimated to have been made during the early period of Goryeo. The two medium-sized wind chimes of the upper-baldachin's northern direction were manufactured through forging a Cu-Sn or Cu-Sn-Pb alloy, and they appear to have a similar structure to the cylindrical wind chimes appearing during the latter period of Goryeo and the Joseon period. The two small-sized wind chimes of the upper-baldachin's southern direction were manufactured by casting a Cu-Sn-Pb alloy containing Zn, and based on the chemical composition of the alloy and the shape of the clapper, they are estimated to have been manufactured during the latter period of Joseon. Through the observation of microstructures and a chemical composition analysis, it is demonstrated that two wind chimes of the lowerbaldachin were manufactured by casting and slow cooling the alloy with an alloy ratio of Cu:Sn:Pb≒80:15:5. In addition, it is estimated that the wind chimes of the upper-baldachin's northeast direction were manufactured by forging an alloy of Cu-Sn with a similar alloy ratio to that of forged high tin bronze. The results of a comparative analysis of prior research on domestic wind chimes confirm that two wind chimes of the lower-baldachin have a similar composition ratio to the wind chime excavated from Wolnamsaji in Gangjin, containing an amount of tin that corresponds with ancient records. Having a similar alloy ratio to forged high tin bronze, the wind chimes of the upper-baldachin's northeast direction are the only instances among all of the wind chimes that have been examined to date that were manufactured using this forging method. The purpose of this research is to collect baseline data to verify and classify the manufacturing period of wind chimes according to their morphological characteristics based on scientific evidence. It is hoped that this data can be utilized for the restoration and conservation processes of the wind chimes of the Stone Standing Maitreya Bodhisattva of Gwanchoksa Temple, Nonsan.