What are the more mature technologies for the protection and restoration of murals in China?

(A) the status quo of murals and pathological records

histogram record

B drawings

C. Damage distribution map

Three-dimensional infrared photography

Three-dimensional laser scanning

The above recording means should be used according to the specific situation.

(2) Analysis of mural materials and structures.

1, pigment

The Sino-Japanese cooperative research on Dandan Uhrik mural is a comprehensive research project including archaeology, art history and conservation. The pigment analysis of murals is not only to understand the production technology and drawing method of Uherik murals in Dandan, but also to provide a basis for the protection and restoration of the lower murals, and also to provide technical data support for the archaeological and art history research involved in this project. Therefore, Chinese and Japanese experts discussed and determined the analysis requirements of different experts for pigments as follows:

A, white (white is the background color, white is the highlight of the Buddha's face)

B, cyan (basically in Buddha's hair)

C, black (original black, black produced by change)

D, red (including slightly bright red)

Danhuang

F, brown

G, gray, purple and horse colors need to be further distinguished.

2, plaster layer

According to the preliminary analysis of the plaster layer samples, the material of the plaster layer is composed of sand and soil. However, due to the small sampling amount and sampling position in the preliminary analysis, it is still necessary to further analyze the chemical composition and structure of gypsum layer in order to increase the understanding and understanding of murals.

A, the chemical composition of plaster layer

B, chemical structure of plastering layer material

C, particle size analysis of plastering layer components

D, the bonding strength of plaster layer

E, whether the mortar layer has fibrous hemp fiber-like substances.

F, micro-morphology of plastering layer

3. The section structure of murals

I. Cross-sectional view of mud layer pigment layer

B, the combination of pigment layer and plaster layer

C. Penetration of surface reinforcing material to pigment layer and plaster layer

4, the means of analysis and testing

metallurgical microscope

scanning electron microscope

x ray diffractomer

X-ray fluorescence spectrum

Laser Raman spectroscopy

Industrial computed tomography

The instruments and means used in the analysis are determined through consultation between China and Japan. In the actual application process, one or more of the above instruments will be used together according to the analysis purpose.

(3) Techniques and materials for the protection and restoration of murals.

1. Problems needing attention in mural protection technology and material selection

The protection technology and material selection of Dandan mural should be considered in combination with the characteristics and present situation of the mural. Therefore, we should pay full attention to:

A the murals have been removed from the site and transported back to the laboratory.

B, when the mural is unveiled, due to the limitations of site conditions, some work that needs to be completed on site cannot be completed, and these links should be supplemented in the laboratory.

C, due to the limitation of item B, there is still work to clean up the dirt on the mural surface.

D, the wall picture has been reinforced on site, and the bonding material for veneering is also B-72. Due to the characteristics of high temperature and low relative humidity, the solvent volatilizes quickly, which leads to insufficient penetration depth and accumulation on the surface. The existence of original materials should be considered when selecting surface reinforcement materials.

E, plaster layer strength is low, loose layered, need to be reinforced.

F, murals exist in a relatively dry environment for a long time, and the future preservation environment also belongs to a relatively dry environment, so we should pay full attention to the selection of materials.

G. The thickness of gypsum layer retained in this mural is inconsistent, and the back needs to be treated.

H, in the process of choosing mural back brace, we should fully consider the mechanical stability of the material.

Me, there are cracks on the surface of the mural, so the cracks in the mural are bonded and strengthened.

J, the selection of all materials must pay attention to its stability, applicability and reprocessability.

2. The principles of mural protection technology and material selection.

It should be emphasized that due to the cooperative nature of this project, this project has the conditions to select materials and technologies in a wider range. The selection of materials and technologies is based on the following situations:

Protection technology of murals in Fallon Jintang, Japan

French mural protection technology (mastered and applied by Xinjiang Institute of Cultural Relics and Archaeology)

Protection technology of murals of clouds and gas pictures of four gods in the Western Han Dynasty in China

These three conservation projects all have successful experiences, and there are also some main materials to choose from around these three projects. These materials basically contain the main materials used in the protection and restoration of murals at present, except for a few cases. During the scheme discussion, the project team thought that in addition to the same materials, the materials used in the three projects could be used for reference to increase the comparative screening of materials. The methods of comparison are material performance test and comparison, and simulation experiment effect comparison. Through the comparison of materials, the materials suitable for the protection and restoration of Dandan mural are screened out. At the same time, on the basis of ensuring the performance, the price and availability of materials are also considered accordingly.

It should also be pointed out that the selection range of materials is limited by the conditions of successful application examples. Performance comparison and simulation test comparison mainly refer to the comparison of this kind of materials.

Protection and restoration of murals

1, mural surface is clean.

Using distilled water, ethanol and other solutions to soften the dirt on the mural surface, combined with physical methods to clean the dirt on the mural surface.

2. Stick falling objects on the wall.

Using HPC made in America and Primal made in France to paste loose objects on the surface of murals.

3. Wall reinforcement

B-72 remains on the mural surface, and B-72 on the mural surface forms a thin covering layer. Due to the harsh desert climate and environment in the process of opening at that time, there was not enough time and materials to strengthen the surface of all murals except a few murals. The application of B-72 on the mural surface is for stickers. Although it also has a certain reinforcement effect on the pigment layer on the mural surface, it still can't play a real reinforcement role because of insufficient penetration depth. In order to effectively reinforce the pigment layer on the mural surface, it is necessary to reinforce the mural surface again.

Considering that there is already a layer of B-72 film on the mural surface, in order to give consideration to the consistency with raw materials, B-72 is still the first choice for reinforcement materials. In order to evaluate and compare the reinforcement effect, comparative simulation tests were also carried out with bone glue, HPC and other materials.

4, veneer protection

In the protection and restoration of murals, in order to ensure that the front of murals is not damaged, it is necessary to cover the front of murals.

Veneer materials: Japanese paper and China Xuan paper.

Adhesives for veneering: B-72, alginate and polyvinyl alcohol (all three materials have been successfully applied, and one should be determined after comparison in specific applications).

5, mural turnover fixture

In the process of restoration and protection, murals need to be turned over. In order to ensure that the murals are not damaged during the overturning process, a wooden splint must be used, and the side of the splint close to the murals needs to be lined with a sponge with a thickness of 5 cm.

6, mural back reinforcement

The thickness of plastering layer on the back of mural is uneven, so the back should be leveled first, and then the plastering layer on the back should be strengthened. It is necessary to compare and test B-72, acrylic acid aqueous dispersion, Site-FX (Japan) and MC to determine the reinforcing substance.

7, mural back reinforcement

On the basis of strengthening the plaster layer on the back of the mural, carbon fiber reinforced B-72 is used to reinforce the back.

8. Interference layer

The interference layer adopts German foam material, QH-B8 (China) and French inorganic cementing material. When the interference layer is bonded with the mural plastering layer, the unevenness of the plastering layer is lined with Japanese plastic epoxy resin.

9. Follow the tool rest

Through the comparison and screening of all-aluminum honeycomb panels produced in China and Japan, the movable support was determined.

10, wall back, interference layer, movable support with glue.

Plastic epoxy resin (Japan), elastic polyurethane structural adhesive (China)

(5) Mosaic combination of murals

Due to the collapse of the east wall of the Buddhist temple, the murals on the wall were broken. According to the records of archaeological cleaning, the preserved and restored murals can be pieced together to better interpret the significance of murals. Therefore, this point should be fully considered in the protection and restoration, especially when making movable supports.