Onsite surveys of the preservation condition and organic damage of wood cultural properties by each harmful cause such as termites were conducted to take proper measures for the prevention of organic damage to wood cultural assets. According to the results of the surveys, wood structures were found to be damaged by harmful insects such as cigarette beetles (Lasioderma serricorne), powder-post beetles, white ants, and bees (Carpenter bees, sphecidae), as well as by other elements such as rot fungi and humidity, causing the rotting, cracking, and breaking damage of wood.

Wood damage by bees

Wood damage by death-watch beetles (Stegobium paniceum)

Wood damage by powder-post beetles

Wood damage by rot fungi

To prevent termite damage on wooden buildings and structures, the conservation team of the National Research Institute of Cultural Heritage places a piece of wood on or in target buildings and structures and monitors it for any signs of infestation. This method of monitoring is effective indetermining the distribution of termite colonies in the surrounding areas of a historic wooden structure. When a sign of invasion is detected in an area, all wooden structures and buildings in the vicinity are treated with insecticides.

monitoring investigation
- Location : Odaegung Palace (2000 ~ 2003)

Fumigation is a method of killing insects and fungi after sealing the wooden cultural heritage in question. It is considered as one of the best ways to protect cultural heritage from insects and fungi because it is effective and does minimal chemical damage to wood. However, the effect of fumigation does not last long, making follow-up treatment necessary. In Korea, the fumigant used is a gas composed of methyl bromide and ethylene oxide mixed in the proportions of 86:14.

Examples of Fumigation (Daeseongjeon of Jangsuhyanggyo)

Spraying insecticides on the foundation of a wooden structure or around it can effectively prevent invasion by termites by creating a shielded zone around the structure. Soil treatment for termite control, however, must be preceded by a study of its potential consequences on water quality in the surrounding area and the health of local residents and the flora and fauna.
Insecticides used for termite control includes Bifenthrin and Kilbe special-60.

Example of Soil termiticide Treatment

National Treasure Jongmyo Jeongjeon (Royal Ancestral Shrine)
- Conducted in August-September 2001

This method of luring termites out of their nests to eliminate the entire colony has little to no impact on the environment, and is hence more environment friendly than methods involving chemicals.
Coupled with regular monitoring, it can effectively prevent the invasion of wooden structures by termites nesting in the surrounding areas. However, luring termites out of their nests, using an attractant, is a rather slow process, taking anything between three and six months.

Efficacy test of Termite Colony Elimination System
- Location: Jongmyo (Royal Ancestral Shrine)

A system of disintegrating an army of white ants

Seokguram Grotto, Gyeongju (Originally named Seokbulsa Temple) was built by Kim Dae-seong commissioned by King Gyeongdeok (751AD), and it was not until 774AD that the temple was completed during the reign of King Hyegong. The man-made granite grotto located halfway up the Tohamsan Mountain has a statue of Sakyamuni Buddha surrounded by smaller status of bodhisattvas, disciples, generals, and Heavenly Kings. Originally a total of 40 sculptures were carved, but only 38 remain today. Seokguram Grotto, Gyeongju is regarded as the best of Silla's Buddhist masterpieces, particularly because it's a seamless combination of architecture, geometry, religion, and art. Seokguram Grotto, Gyeongju is listed as National Treasure as well as a UNESCO World Cutural Heritage Site.

Repair and maintenance of Seokguram Grotto, Gyeongju

The damage of Seokguram Grotto, Gyeongju was done in around 1905 by the Japanese army in the process of cracking down on Korean voluntary civilian army who rebelled against Japanese invasion and in the process of the Japanese pillage of Korean cultural assets. The frontal part of the grotto was collapsed and part of the ceiling of the grotto was damaged by the Japanese army at the time.
Japanese attempted to repair the damage several times to hide their atrocity inflicted on the cultural assets, but they ended up causing irreparable damage to Seokguram Grotto, Gyeongju. However, Japanese attribute the cause to our insufficient investigation.

1. Repair during the Japanese Colonial Period (1910-1945)

The Japanese carried out repair works three times during this period, removing the moss from stone surfaces with steam in 1933 and 1945.

• First Repair Project (1913-1915)
  • Before repair works, one-third of Seokguram's ceiling had fallen off and the remaining part of the ceiling was in danger of collapsing. Also, a large portion of the cave temple was buried under a landslide. But as repairs were focused too heavily on replacing the destroyed stone blocks and reinforcing the walls, the surfaces of the grotto were turned into one giant piece of concrete.
• Second Repair Project (1917)
  • After the first round of repairs, Seokguram'sceiling and walls began to leak. Mortar and clay were applied on the leaking areas.
• Third Repair Project (1920-1923)
  • Even after the second round of repairs, the ceiling and walls continued to leak. So a waterproof layer and a drainage system were installed.
• Repairs in the Late Colonial Period
  • After the third repair project and toward the end of the Japanese occupation, the leakage continued and the surfaces were covered with green moss. There is a record stating that steam was used to remove the moss in 1933 and 1945

2. Maintenance after Liberation

After Korea's liberation from Japan in 1945, Seokguram Grotto, Gyeongju was left untouched due to the Korean War (1950-53) and ensuing social chaos. But after a cleaning project in 1957, more people became interested in the grotto and worried about its state of preservation. A conservation committee was formed and extensive research took place from 1958 to 1961. From 1961 to 1964, the special committee built wooden structures to support the grotto. A fourth round of repairs was carried out to build another waterproof layer. But condensation continued to be a problem, so an exit door and air conditioning system were installed as a prevention measure. Partial repair works were carried out from 1976 to 1977 to install protective glass walls, improve the lighting, and expand the front base.

3. Conservation Environment of Seokguram Grotto, Gyeongju

Although the leaks were repaired after a secondary dome and protective walls were installed during the repair works from 1961 to 1964, an air conditioning system had to be installed in 1966 to prevent condensation through the control of temperature and humidity levels inside Seokguram. The air conditioning system is replaced every 10 years, and the current system was installed in 2005.

• Investigation of Conservation Environment
  • At Seokguram Grotto, Gyeongju, temperature and humidity sensors (3 sensors inside the grotto; 2 sensors in dual dome) and one carbon dioxide sensor (One inside the grotto) were installed since 2007 for the real-time monitoring of conservation environment through a remote monitoring system.