How to protect ancient buildings

Cultural relics protection technology is a comprehensive professional knowledge, including the production and protection of cultural relics, science and technology related to prevention and control, material properties, operation technology and various investigations and experiments. Cultural relics are destroyed by two factors in the process of preservation, namely: ① man-made destruction. For example, ancient buildings, cave temples and ancient tombs were burned, demolished or improperly maintained by the war and lost their original appearance; Copper and iron ware, calligraphy and painting, bamboo and wood lacquerware, ceramics, etc. are damaged due to improper protection and handling. (2) Natural factors such as wind, rain, thunder, electricity, fire, earthquake, light, insects and mildew damage cultural relics.

China has a long history in the protection of cultural relics. In the Tang dynasty (6 18 ~ 907), it was recorded that wooden wedges were used to straighten the beams of ancient buildings. According to Huang Xiufu's "Yizhou Famous Paintings", the murals of three walls in Chengdu are still intact after more than 200 years. The uncovering technology of painting and calligraphy protection was quite mature in the Tang Dynasty. "Paint sticks to stone, paint sticks to wood" is a long-standing traditional skill to restore stone and wood cultural relics. Later, with the progress of science and technology, polymer materials and physical detection technology were gradually introduced into the protection of cultural relics.

In some European countries around the18th century, the traditional technique of repairing murals with Kesein mixed milk and limewater has been passed down to this day.

The protection of cultural relics should follow the principle of prevention first and maintenance second. The moistureproof, leakproof, fireproof, lightning protection and shockproof of immovable cultural relics are mainly solved by engineering technology, and the method of combining engineering technology with chemical treatment is mainly used to prevent insects and birds.

When the pollution of dust, sulfur dioxide and sulfur-containing compounds in the atmosphere to cultural relics exceeds the national standards, the sources of pollution should be removed. If the pollution is within the allowable range of national standards, the environment should be green, pollution should be reduced, and new pollution sources should be strictly controlled.

For the protection of movable cultural relics, first of all, we should pay attention to the protection measures such as moistureproof, shockproof and mildewproof of museum warehouses and showrooms, and then protect various cultural relics with different textures, such as copper and iron rust prevention, masonry cultural relics windproof, silk paper mildew prevention, moth prevention and aging prevention.

Repair technology: the whole wooden building is crooked, then straightened and strengthened. Local damage of components should be repaired and butted. Large decayed hollow members can be reinforced with polymer materials such as unsaturated polyester resin, and those with serious decay can be replaced according to the original system.

If the masonry structure of ancient buildings is skewed as a whole, it should be observed at fixed points and regularly. After reinforcement and stability, no foundation treatment will be done. Cracks can be reinforced by hoop and grouting, and incomplete masonry can be repaired. If it cannot be repaired, it can be partially or completely demolished and rebuilt as it is. The cracks in the mountain of Cave Temple are reinforced by shotcrete or grouting, and the seepage and leakage should be diverted and intercepted. The surface weathering of stone relics such as stone carvings and stone carvings should be sealed with silicone polymer materials.

In the restoration of ancient buildings, minor repairs should not be carried out, and the parts that can be partially demolished should not be completely demolished. The original components should be preserved as much as possible to preserve the historical value of ancient buildings. For the artistic components such as carved tiles, wood carvings, brick carvings and stone carvings in ancient buildings, we should handle them carefully and try not to change them or change them less. Statues, murals, colored paintings and other ancillary works of art cannot be repaired at will.

The restoration of movable cultural relics can be carried out by combining traditional technology with modern technology. For example, the rust of bronzes can be removed by mechanical methods or electrolytic reduction. Bamboo lacquerware can be dehydrated by natural drying, alcohol ether combined with soaking, freezing sublimation, osmotic polymerization of polymer materials, etc. Most of the damaged paintings and calligraphy are repaired by traditional uncovering and mounting methods; Modern books and periodicals can be reinforced by screen printing; Ancient silk screens can be fumigated and disinfected; Fragile textiles can be reinforced by screen or traditional installation methods; Ceramics are destroyed by polymer materials such as shellac or epoxy resin.

The new materials and new techniques used in the restoration of cultural relics must ensure that they do not damage the historical value of cultural relics, including their shape, material, color and strength, and are reversible at the same time. The new materials used in the maintenance of ancient building components should also abide by the principle that they can only be reinforced and cannot be replaced.

Detection technology is mainly used to detect the traces of cultural relics, analyze the chemical composition of texture structure and determine the age. X-rays and ultrasonic waves are commonly used in flaw detection; The analysis of tissue structure is often observed by electron microscope and metallographic microscope; The chemical composition of cultural relics is usually analyzed by spectrum and mass spectrometry; For vague ink paintings with little contrast, infrared photography can be used; Carbon-containing substances such as wood can be dated by carbon fourteen; Tiles can be dated by thermoluminescence.

Protection technology of stone cultural relics

The preservation technology of stone cultural relics is influenced by natural forces such as sunlight, water erosion, earthquake, environmental pollution and microclimate change. , will cause pulverization, discoloration, mildew, cracking, alkali cracking, cavitation, condensation, collapse and overturning.

The protection technology of cave temples should first investigate the diseases. The investigation includes the following steps: ① Surveying and mapping topographic map, cave area plan, elevation map, vertical and horizontal section map, etc. Surveying and mapping methods include theodolite traverse survey, control network survey and small plate survey. Close-range photogrammetry can be used for elevation measurement and mapping of cave stone carvings. ② Environmental quality assessment. Including the stratum, lithology, structure, hydrogeological conditions, meteorological, hydrological and seismic data, pollution sources and harm caused by the mountain where the cultural relics are located. The main hazards and control measures of cultural relics should be pointed out. ③ Geophysical exploration. For solving a special purpose, it can only be effective if the physical premise and necessary working conditions are met. At present, the geophysical methods used include: DC resistivity method to find the seepage path, microelectrode system method to detect the thickness of weathered layer on the surface of grottoes, acoustic wave method to measure the weathering degree of grottoes, seismic exploration to carry out pre-grotto archaeology and so on. ④ Stability analysis. Many grottoes are located on steep slopes and belong to a three-dimensional space combining steep slopes and caves. To analyze its stability, we should study the lithology, cracks, deformation and failure process, mechanical analysis and calculation of the mountain where the cultural relics are located, and predict its deformation and failure law. For large dangerous rock mass, structural plane analysis and calculation should also be carried out.

Preventive measures refer to improving the environment where cultural relics are located and avoiding the continued destruction of various weathering stresses. The main measures are seepage prevention and drainage at the cliff top of grottoes, changing and dredging the direction and position of surface water flow, and cutting off the connection with caves; Find out the direction and scope of cracks to prevent surface water from infiltrating into caves along cracks; Using the ground drainage in front of the tunnel to reduce the groundwater level; Eliminate moisture and dew in caves, prevent violent alternation of dry and wet, and prevent water from eroding cultural relics. In order to prevent works of art from being directly attacked by sunlight, rain and wind and sand, the eaves of caves can be built for protection.

The reinforcement of cave temples is mainly to prevent cave collapse and artistic weathering.

The measures are as follows: ① Use retaining wall, retaining wall, large masonry or pouring body to prevent crack development, prevent hanging rock from collapsing and resist rock cracking. This method is difficult to maintain the status quo of the grottoes, and it is easy to destroy the historical relics of the cliff walls, so it is only used when necessary. (2) Shotcrete and anchor support. Anchor rods (coarse steel bars) with different lengths pass through fractured rock mass horizontally or obliquely from different directions, anchor unstable rock mass on stable rock mass, then weld the end of anchor rod with fine steel mesh, spray concrete with a thickness of 5 ~ 15cm on the surface with high pressure, and then cover it with rock powder to make it old.

Drainage holes are set at regular intervals, so that a small amount of water seepage can still be discharged. This method is suitable for the grotto mountain with slack, many cracks, dense caves and broken rock mass.

It can be reinforced, supported and windproof, with large bearing capacity and large safety reserve. The disadvantage is that it will partially change the appearance of the grottoes and cover up some historical sites. ③ Grouting and bonding. It is one of the reinforcement and protection methods for the fracture of carved works of art in grottoes, the cracking and collapse of cave walls and cliffs. At present, the main grouting bonding materials used are epoxy resin, acrylate and inorganic chemical materials. The material performance requirements are close to the physical and mechanical properties of the reinforced rock, and meet the requirements of good cohesiveness, low viscosity, good groutability, room temperature curing, freeze-thaw resistance and water resistance. Grouting equipment mainly adopts air compressor and special grouting barrel. Check the grouting depth, range, rock mass strength and deformation characteristics to ensure the grouting reinforcement quality.

The protection technology of open-pit stone cultural relics is to study the weathering forms of stone carvings and classify the weathering reasons. Then, according to the long-term observation records of meteorological elements, water damage and humid environment, samples were systematically taken according to the weathering depth of stone carvings, and the main causes of stone carving weathering were found out by testing rock physical and mechanical properties, chemical analysis of rock oxides, thin section identification, differential thermal analysis of weathering products, X-ray diffraction analysis, spectral analysis and scanning electron microscope observation. The point load strength test and ultrasonic test are used to detect the weathering degree of stone carvings, and then the weathering depth of stone carvings is detected by geophysical exploration and lithofacies identification according to the change of petrochemical composition with depth.

Generally, open-air cultural relics that are relatively complete and not seriously weathered are improved to protect the environment. Protective materials can only be used for cultural relics with severe weathering, no protection and no preservation. The use of protective materials should be clear about which weathering forces should be mainly prevented, and the main indexes that should be achieved after protection should be put forward. The materials should be colorless, transparent, non-reflective, non-corrosive, good in chemical stability, strong in permeability, weathering resistance and certain in consolidation strength. Commonly used protective materials are polymer organic polymer materials (silicone, polyurethane, methacrylate, silicone, etc.). ) and inorganic chemical materials.

For the safety of cultural relics, it is necessary to carefully test the properties of the protective layer materials of stone carvings, including: ① the material form, filling degree and changes along the depth direction in the protective layer; ② Physical and mechanical properties: such as porosity, air permeability, consolidation strength, wear resistance, etc. ③ Water erosion resistance: such as surface water absorption (capillary water absorption), maximum water absorption, hydrophobicity, water permeability, etc. ④ Weather resistance: such as aging resistance (including artificial aging test and natural exposure field), freeze-thaw test, stability test, dry-wet alternate test, etc. ⑤ Chemical stability: such as acid resistance, soluble salt and moderate soluble salt content, anti-pollution ability, etc. ⑥ Repainting: the possibility of providing protection for future generations.

Protection technology of stone cultural relics in the collection Stone cultural relics collected from tombs or in the wild need to be descaled to remove all kinds of salts or microorganisms contained in them. The main methods are: ① removing soluble salts. Generally, it is soaked in tap water for a long time, and then soaked in deionized water. Large stone tools can be coated with pulp, dried and taken out. ② Surface descaling. Put it in an ultrasonic cleaner and wash it off quickly. Marble rust shell can be sealed with dimethyl resin, then corroded with dilute acid, and then removed mechanically. Other stone tools can be softened with dilute acid to dissolve dirt, and finally washed with deionized water. ③ Adhesive repair. The bonding material is generally an adhesive made of epoxy resin mixed with stone powder and a small amount of pigment, and nitrocellulose or polyvinyl acetate can also be used to bond severely weathered stone tools. For the stone cultural relics that have been quite loose or painted on the surface, materials such as methyl acrylate, polybutyl methacrylate, polyvinyl acetate, epoxy resin, silicone and barium hydroxide are selected for infiltration reinforcement before bonding. Commonly used repair materials include gypsum, 10% celluloid mixed acetone and amyl acetate solution, fine stone powder, polyvinyl acetate emulsion, stone powder and amorphous silicon dioxide, and pigment paste for repair.

restoration techniques of Grotto Paintings

The restoration technology of grotto murals, the murals in grottoes are usually dug first, and then painted on the uneven stone walls. Murals in the Northern Wei Dynasty, the Western Wei Dynasty and the Northern Zhou Dynasty were all painted with two layers of wheat straw mud, without background color, and directly painted on rough mud walls. Grass mud layer, pigment layer and grass mud layer are closely combined with each other, and generally there will be no peeling and peeling, but there will be small cracks in some walls.

During the Tang and Song Dynasties, the mud layers of murals were generally 3-4 layers, and the types of mud layers increased. In addition to the wheat straw mud layer, there are mud layers such as hemp knife, cotton and cattail. Before painting, apply a thin layer of white powder on the battlefield surface. This white powder coating will crack and peel off when it is wet, which is generally called nail cracking. When the humidity is serious, it will be crisp with the mud layer on the ground, which is called crisp powder disease spot.

There are also some murals whose mud layers are too thick, or which are heavy murals added to the previous generation by later generations. Due to the influence of humidity, earthquake and rock cracks, some murals are separated from the rock wall, forming cracks and cavities, and murals are in danger of falling off in a large area at any time.

During the Five Dynasties, there was a mural made on the rock surface outside the cave, also called outdoor mural. Ground combat is to first apply two layers of grass mud on the rock wall, then apply a layer of hemp knife lime plaster, or directly apply lime plaster on the rock wall, and then paint it. This kind of lime ground war will also appear empty drum or a small area far away from the rock mass.

The repair methods of the above diseases are as follows:

① Repair method of nail crack in white powder painting layer of mural painting. Firstly, remove the dust and sand accumulated inside and outside the coating layer of nail polish remover, inject a mixed adhesive made of 2.5% polyvinyl alcohol aqueous solution and 65,438+0% polyvinyl acetate emulsion with a volume ratio of 4 ∶ 65 and 438+0 between the coating layer and the mud layer, stick the coating layer back to the ground, then compact it with a cotton swatter wrapped with white silk, and wait until the water injected into the adhesive of the painting layer by nail polish remover precipitates, and then add it to the painting layer with a volume ratio of 4. If there are missing lesions, bubbling will appear after spraying, and adhesive can be injected again to repair them. When the spraying agent is slightly dry, spread white silk on the surface of the mural and roll it evenly with a soft rubber roller. The color of the mural restored by this method is free from damage and glare, and the original appearance of the mural can be maintained. The drug is reversible and does not affect the repair. China Dunhuang Mogao Grottoes 1000 square meters cracked mural of armor promotion was successfully repaired by this method. After 25 years' inspection, it has not been upgraded again.

② Repair methods of brittle and powdery lesions in wall mud layer. The repair process is basically the same as the white powder painting layer, except that the mixture of polyvinyl alcohol aqueous solution and polyvinyl acetate emulsion with different concentrations or simple polyvinyl acetate emulsion and acrylate emulsion is injected into the depth of the mud layer according to the object, and then compacted.

(3) The method of repairing the mural's separation from the rock mass and the hollowing of the painted wall. Some grass mud mounds in murals are separated from rock masses. First, a layer of polyvinyl acetate emulsion is coated on its edge, and then clay, sand, hemp knife or wheat straw are mixed with 15% polyvinyl acetate emulsion to form a paste, and the paste is filled on the edge of the mound, so that the coated wall can be firmly attached to the rock mass. In order to make the restoration consistent with the color of murals, appropriate pigments can be added to the mud.

When the painted wall is empty in a large area, it can be pasted by pressure grouting (glue) or repaired by combining grouting with riveting.

A small part of the wall painting of the lime battlefield has been hollowed out. Gauze strips soaked with epoxy resin or polyvinyl acetate emulsion can be filled into the hollow part between the battlefield and the rock mass from the breach of the painting wall, and appropriate pressure can be applied evenly to make the painting wall and the rock mass closely combined, and then it can be cemented after the glue is dry. The cracks in the whitewashed wall are filled with 15% polyvinyl acetate emulsion sand and lime putty. Before filling, coat a layer of polyvinyl acetate emulsion on the edge of the painted wall. This can not only make it more firmly bonded, but also prevent the water in lime plaster from infiltrating into the surface of the mural and leaving spots.

Protection and maintenance technology of ancient buildings and tomb murals

Preservation and restoration technology of murals in ancient buildings and tombs; murals in ancient tombs in ancient buildings should generally be preserved in situ, and can be moved for protection under special circumstances.

After in-situ protection and reinforcement of murals, it is necessary to improve indoor ventilation, moisture-proof, sun protection and other protective facilities. Tomb murals are mostly preserved under natural conditions after reinforcement, and the reinforcement method of murals depends on the damage.

When the picture is seriously degummed, spray 1 ~ 2 times with 2 ~ 3% glue alum water or 2 ~ 5 polyvinyl butyral and other polymer materials. The reinforcing agent is the same as the degumming treatment when the surface of the picture is brittle and alkaline, but the concentration of the agent increases and the spraying times increase. When the mural surface is thin and brittle, and the inner layer is brittle and alkaline, it is necessary to adopt the method of injection and degumming the medicine. Work needs to be done one by one, one by one, and the number of injections depends on the picture. The drugs used should be diluted first and then concentrated.

If the mud layer of the mural is empty, it should be riveted with dry mud. Drill 2-3 small holes per square meter on the picture of wireless bar, make dry hard gray bar or mud bar with white ash or sand mixed with polyvinyl acetate emulsion or polyvinyl butyral and squeeze into the holes, and the mural mud layer is firmly attached to the wall; Serious cracks, with the same dry mud material into the cracks. Part of the picture falls off according to the mud layer of the original mural and is painted as usual.

Migration protection is divided into three steps: removal, repair and installation.

Uncovering will completely separate the mural from the wall. Small murals can be uncovered in a single block, and large murals should be uncovered in blocks, each block should be 1 ~ 3 square meters; When the height of the picture exceeds 2.5 meters, it needs to be uncovered in two or three layers.

Before unveiling, a series of preparatory work should be done, mainly including the copying of murals, the investigation of murals and wall structures, the drawing of the block size map of unopened murals, the block number relationship size map and so on. Then according to the size of the block, murals and wall structure to determine the way to open. Commonly used methods are as follows:

(1) Tear down the fence. First, use 40% peach gum solution or 10 ~ 20% polyvinyl butyral to cover the picture with a layer of white yarn to protect the picture. After drying, install the front wall plate and demoulding table as shown. Saw off the side seams on the four sides of the wallboard with a knife, with a seam width of 5 ~ 8mm, and then dismantle the wall blocks in sections from top to bottom, each section being 50 ~ 70cm high. When approaching the bottom edge, it is necessary to quickly turn over the front wallboard, push it inward together with the mural mud layer, and lay it flat on the stripping table.

Go to the repair room for repair.

② sawing. When the mural has more than two mud layers and the thickness is more than 2 cm, the mud layer and the wall surface are sawed off with a saw blade.

(3) pry. When the mud layer of the mural is empty, pry it off the wall with a flat shovel.

(4) Shock. When the local mud layer of the mural is firmly attached to the wall, gently chisel it between the mud layer and the wall with an iron drill, mainly by vibration to make the mural leave the wall. In the same painting, sawing, prying and shaking are often mixed together.

5 take it. When murals are earthen walls, they can be photographed in wooden boxes.

Nail the side plates in the boxes around the front wall, embed them in the earth wall, put the murals in the boxes, and then cut the earth wall to make the murals leave the wall.

⑥ stuck. When murals are painted directly on brick walls or stone walls, they can be glued with adhesive tape. Stick a piece of white cloth coated with polymer materials such as 10 ~ 15% polyvinyl butyral on the picture to make the color layer of the mural firmly stick to the adhesive tape. After drying, remove the tape and the mural will be removed together with the tape.

When repairing a mural with mud layer, the back of the mural should face upwards, and shovel the mud layer at the bottom of the mural with a flat shovel to keep the mud layer on the surface of the mural. 2 ~ 5% alum water or polyvinyl acetate emulsion and other polymer materials 1 ~ 2 times should be sprayed for reinforcement, and the reinforcing agent cannot penetrate into the wall painting. After drying, apply a new mud layer, and the thickness of the surface layer is generally 1.5 ~ 2.5 cm. The material ratio of the new mud layer is the same as that of the surface layer, and it is made of high molecular materials such as white ash or sand mixed with shellac or polyvinyl alcohol. Then stick a layer of epoxy gauze to prevent electric shock. Finally, the back is bonded with epoxy resin to form a base for supporting murals, which is a wooden cabinet or light metal cabinet in cross format. The cabinet is reserved with iron movable mortises for easy installation. After the back is repaired, turn the wall upside down, remove the gauze and residual glue, repair the damaged part with raw materials, and uniformly fill the color after installation.

When pasting a mural without mud layer with adhesive tape, the base should be made according to the size of the block, and the surface nail plate should be painted as old as the original wall. Then stick the painted surface of the adhesive tape on the substrate, wet the adhesive tape with the diluted solvent of the adhesive material, and gently remove the adhesive tape, leaving the color layer of the mural on the substrate.

To install a small mural displayed in a museum or several murals assembled together, just install a bracket suitable for visiting on the back of the restored mural.

When installed in the original position in the original building, the wooden bracket or metal bracket for hanging murals should be installed above the lower shoulder of the wall according to the building structure. When there is a picture on one side of the wall, use a single-sided bracket; when there is a picture on both sides, use a double-sided bracket. The support consists of several columns and transverse pillars. Columns should be firmly connected with the building frame, and then installed wall by wall in the numbered order. First, connect the base on the back of the mural with the pillar of the bracket with iron pieces. At the same time, use the mural to block the size drawing, and then fix the iron pieces after repeated verification.

During installation, the moisture-proof ventilation of murals should also be considered, and a moisture-proof layer should be added at the bottom of the wall. On the unpainted side, build by laying bricks or stones a thin solid outer wall, and there should be a gap of 5 ~ 10 cm between the outer wall and the bracket to facilitate the ventilation on the back of the mural; When installing important murals, this gap is generally not less than 50 cm to prevent staff from entering to check the safety situation.

Finally, the artists mended the saw seams between blocks and made up lines according to the copy to restore the original appearance before opening.