Concerns about brick and stone artifacts
My Son relic site currently has 40 temples, a system of surrounding walls and 1,803 artifacts, mostly made of sandstone, ceramics, and terracotta (architectural components, decorative sculptures, altars, statues of gods, sacred animals, ritual objects, etc.).
Specifically, there are 708 artifacts on display in the relic site and 93 artifacts on display at the My Son Museum, the rest are preserved in storage.
According to the My Son Cultural Heritage Management Board, preserving materials at My Son relics as an open museum when most of the artifacts are displayed outdoors in the harsh environmental conditions of My Son valley is always a big challenge.
In particular, climate change leads to more sunshine and rain, causing the expansion of temples and artifacts to be more affected, making them more susceptible to cracking, chipping, and moss and mold invasion.
Besides, the preservation of stone artifacts (door pillars, door steps, lintels, wall decorations, corner decorations, fire ears, tower tops, altars, steles...) or other materials such as laterite (G tower group), stone - gravel in the wall core (F towers); or decorative ceramics, terracotta roof tiles, cobblestones used to reinforce foundations, build wall cores... also faces difficulties.
In fact, since the 1980s, the temples and towers of My Son area B, C, D have been reinforced, in which the reinforced brick material mainly reuses old bricks and is bonded with cement mortar.
However, moss, mold and microorganisms grow a lot, destroying the surface of the restored bricks and spreading to the original walls. With the restored towers A, H, K, E7 (2003 - 2022) using restored bricks and bonded with otter oil, lime mortar..., after a short time, the phenomenon of salt and rot appeared on the surface of the new bricks and moss and mold appeared very quickly.
In order to preserve artifacts and relics, the My Son Cultural Heritage Management Board has recently carried out periodic cleaning every two months. In addition, it also regularly clears the outside walls of the towers to create an airy space.
Particularly, the phenomenon of fungi, mold, and lichens clinging to the surface of relics and artifacts displayed outdoors or some artifacts displayed attached to the walls of towers D1 and D2 also face the phenomenon of moisture and mold sticking for a long time.
Even through inspection, there was a phenomenon of surface decay, causing deformation and the risk of not being able to recognize the carved patterns on it, losing the value and durability of the artifact.
Find conservation solutions
To preserve the brick and stone materials of the relic, since the late 20th century, several experiments on preserving the surface of bricks on the temple towers have been carried out by the My Son Cultural Heritage Management Board by boiling otter oil and applying a thin layer of it to the original brick surface at tower D2.
Through observation and monitoring by the staff at that time, in the first 2 years, the moss and mold phenomenon decreased significantly. However, after that, the lichen and mold gradually returned to normal like the symmetrical wall. When the E7 tower was renovated in 2015, they also tested preserving the newly renovated brick surface on the tower roof with a thin layer of otter oil. Up to now, the otter oil protective layer has also faded and is no longer effective.
In 2018, Indian experts restoring the H tower group also tested otter oil covering a newly restored 1m2 wall in the north corner of the H1 tower. In the first 2 years, the wall was bright and different, but in the following years, when the otter oil layer gradually faded, there was no difference between the preserved wall and the symmetrical wall.
In 2017, the Institute for Monuments Conservation coordinated with the My Son Cultural Heritage Management Board to test the preservation of the wall surfaces of tower F1 (indoor) and tower F2 in the natural outdoors. This preservative basically helps the brick surface to be hard and greatly limits the invasion of moss, mold, and lichen. However, the color after preservation feels new, not close to the natural color of ancient bricks.
In April 2022, the My Son Cultural Heritage Management Board continued to coordinate with the Institute of Monuments Conservation to conduct a trial treatment of mold, lichen, moss, and algae on the surface of brick and stone materials at a specific location at towers B4 and E7.
The test site is located in wall sections that are in different stages of restoration and reinforcement, and are exposed to different weather conditions, with the surface of the material being damaged by mold, lichen, and algae. The test site has little impact on the activities of the relic site.
The technical team chose a hot, sunny day with dry tower walls to clean the surface of the bricks and stones of moss, fungus, and lichens, carefully, without affecting the original elements. Then, they sprayed a thin layer of chemicals on the surface of the tower walls and the stone pillars. The results were quite positive, but this was only the first step and needed to be monitored.
According to Mr. Tran Quoc Tuan - Deputy Director of the Institute for Monument Conservation, with the advancement of science and technology, advanced methods of monument preservation such as chemistry, physics and biology are being applied more and more popularly in the world today.
The trend of chemical preservation, especially with materials in relics such as bricks and stones, is being researched, developed and widely applied. This method has brought about initial positive results, meeting the strict requirements of maintaining the integrity and increasing the sustainability of the relics.
Source: https://baoquangnam.vn/thach-thuc-bao-quan-gach-da-tai-my-son-3143176.html
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