Mis à jour : 9 nov. 2020
By Chaehoon Lee
During my Masters Degree program in Conservation & Restoration at Korea National University of Cultural Heritage(KNUCH) in Buyeo (2017-2018) and during an Andrew W. Mellon conservation fellowship at the Metropolitan Museum of Art (2019-2020), I have studied Asian musical instruments’ typical surface treatment called Nakdong (Figure 1). In this post, I want to introduce the Nakdong technique's use on musical instruments and discuss why conservation of this particular method needs further study.
After constructing the main body and joining the parts with adhesive where needed, the surface of wooden musical instruments is usually finished by applying various surface techniques to protect the wood. In Western wooden stringed instruments, traditionally a varnish is used, which can be any combination of drying oils, resins, and various solvents that protect and decorate the surface. Its application enhances the grain of the wood, protects it from dirt and humidity and is sometimes believed to benefit the tonal qualities of the instrument.
In traditional Asian instruments, on the other hand, Asian lacquer, natural mineral or organic pigments mixed with animal glue, or a typical heat treatment, called Nakdongbub (낙동법: 烙棟法) in Korean, are commonly used. The Nakdong technique is a scorching technique applied to the surface of the paulownia wood by using a hot iron. The meaning of the character, Nak(낙: 烙) is scorching, Dong(동: 棟) means paulownia wood, and Bub(법: 法) stands for technique.
The exact origin of the Nakdong technique is not known, but can be traced back to the period of Three States in ancient Korea (BC 18 ~ AD 660). The words Gayageum and Geomungo appear in the Samguk Sagi (history book of Three States in the ancient Korea, 1145). They appear continuously in the historic musical instrument related books, Koryo Saakji (history book of Goryo Dynasty's music, 1451) and Akhakguebum (history book of Joseon Dynasty's music, 1493).
During the Joseon Dynasty (1393~1897), an official government organization, was established for manufacturing and repairing musical instruments. This governmental organization ensured that traditional instrument making techniques were passed on to selected masters, who would pass on their knowledge to one or two pupils. Thanks to this system of handing down intangible heritage in Korea, the application of the Nakdong technique remains in use to this day.
Some string instrument masters like Yun Jong-gook in Incheon city and Go Heung-gon at Go Heung-gon Academy of Korean Instruments in Kyeongki province continue to use this method. These masters are designated as Korean National Intangible Cultural Property No.42 Akkijang (musical instrument making master), which is a status reserved for those who have mastered the traditional construction methods and techniques of Korean musical instrument making. To further safeguard the traditions of Korean instrument making, a village called Nangye Kukakchon (Nangye is a nickname for Park Yeon, one of three most credited Korean music masters, two others are Wang San-ak and Woo Ruek; Kukakchon means a village of Korean Traditional Music) was established at Chungcheongnam-do district in 1977.
Korean instrument makers work and live together in this village to pass on the traditional style. In addition, these makers also research and innovate, including improvements made to Korean instruments in the 20th century. For example, in the case of the Gayageum, original instrument had 12 strings but makers have added strings making improved Gayageum with17, 18, 21, 22 or 25 strings using traditional building techniques, but with the ability to have a wider range of notes.
In contemporary Korea, many people are losing interest in the traditional music. If this trend continues, most traditional music may disappear. Fortunately, many fusion music styles are being created. For instance, playing the Gayageum with a violin or a cello. To keep the traditional method, the Akkijangs pass on both traditional and improved making knowledge to their pupils. Musical instrument masters still use the Nakdong technique because it has many beneficial effects, which are referred to in musicology papers as well as in oral tradition. Nakdong’s effects are shown to be beneficial in moderating the effects of changes in temperature and humidity and in combatting bacteria. Storage cabinets treated with this technique on all sides, help to protect their content by keeping away insects and fungi (Bae, 1988).
Newly cut paulownia wood is white and soft, and the color slowly turns dark over time as the wood tissue deteriorates. For aesthetic purposes, the darkening color of the wood surface was covered by the method of scorching and scrubbing the surface (Cho, 2005). The treatment helps to prevent pests and corrosion caused by moisture (Kim, 2011). In my master thesis, I was able to confirm several advantages of this treatment, such as waterproofing, improved sound quality, and pesticidal effects (Lee, 2018).
After finishing my masters’ research, my next question was “what is the long-term effect of Nakdong treatment on the conservation of musical instruments?” That is to say, “does this surface layer still protect the musical instruments from the main wood deterioration factors such as light, humidity, and insects after being stored in a museum for a long period of time?” I examined the deterioration of its surface by analyzing the cellulose and lignin deterioration tendency with Fourier-transform infrared spectroscopy (FTIR), a colorimeter and a microscope to see what the state of the surface was. Working with various historic instruments from The Met, I realized that there were more diverse surface colors than I had witnessed in the Korean makers' surface treating method (Table 2). As the dirt and the treated surface were similar in color, when the surface was dry cleaned, it was not easy to distinguish the level of cleaning with the naked-eye and it was difficult to identify the components of removed parts, as being either carbon particles emerging when the makers finished the surface, or dust accumulating while the instrument was stored in the museum. It’s important not to remove the carbon particles when cleaning as they are part of the original treated surface.
There are however no safe cleaning methods established for cleaning instruments with the Nakdong technique surface treatment and experiments were needed to test a variety of cleaning systems. Therefore, a mock-up sample was created and a synthetic soiling mixture was applied on its surface. For cleaning, a filbert brush, a cosmetic sponge, Evolon (microfilament textile), and borax gel (PVA 4%, Borax 1%) were tried (Figure 2). Cleaning with these tools, burnt wood particles were sometimes removed, therefore additional experiments need to consider other methods like an anti-absorptive gel to avoid the loss of original material. Due to the pandemic and the museum closing, these experiments had to be prematurely stopped.
Nakdong technique is a typical traditional surface treatment used on Eastern Asian musical instruments, ships, furniture, etc. but there are not many studies comparing this technique to those applied to the Western musical instruments. Although some benefits of Nakdong technique are confirmed by my previous study, the durability and other aspects still need further examination.
Bae Mansil (1988). Traditional Korean wooden furniture. Korean cultural series, South Korea
Cho Hoonsang (2005) Usage of the nakdong technique (method to iron paulownia panels) in furniture design. Dissertation, Hongik University.
Kim Bokgon (2010) A study on the improvement and manufacture method of traditional musical instrument on the basis of Akhakgwebeom. The society of Kangwon province folkart 24: 339-378
Korea National Intangible heritage, musical instrument maker
Chaehoon Lee studied the conservation and restoration of cultural heritage at the Korea National University of Cultural Heritage. She presented numerous papers on material analysis on the artifacts and researched Western and Asian string musical instrument conservation. Recently, Chaehoon Lee was an Andrew W. Mellon Fellow at the Metropolitan Museum of Art (2019.09~2020.08). In addition to this, she experienced some conservation-related works at Laboratorio Arvedi di Diagnostica Noninvasive, Cremona, Italy, and Gugak Center, Seoul, Republic of Korea.