Cultural relics protection technology
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 products, calligraphy and painting, bamboo and wood lacquerware, ceramics, etc. Damage 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, the traditional technique of restoring murals with a mixture of milk and limewater was used in the18th century and has been passed down to the present.
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 multiple cracks that have been relaxed.