| Tomb murals occupy an extremely important position in the history of Chinese painting because of their wide distribution,various classification and fine production.However,after a long history,the tomb murals appeared various diseases due to various natural and man-made destruction,which had a serious impact on the picture integrity of the tomb murals.A series of studies on the disease of tomb murals have been carried out by cultural relics conservators.The results show that the migration of water and salt is one of the main factors causing salt damage to tomb murals.Therefore,this paper carried out a capillary water migration experiment and capillary salt transport experiment to study the influence mechanism of ground layer diseases,and through the design of disease simulation experiment,comparative analysis of the best protective materials,to provide more scientific basis for further protection of tomb murals.In this paper,the mechanism of water and salt migration and transformation of tomb murals and the selection of commonly used mural reinforcement materials are studied,and the main conclusions are as follows:(1)The research results of water-salt migration and transformation mechanism in tomb murals show that:1)In the capillary water migration test,the water content decreased first and then increased with the increase of the height of the simulated ground pole test block,while the conductivity and cationic and cationic ions increased slowly first and then increased rapidly.The salt gathered and crystallized at the top,and the simulated ground pole test block had a drying effect.2)In the capillary salt transport experiment with different salt solutions as capillary transport solutions: under the action of the drying effect,the water content and electrical conductivity of the ground pole test block showed a trend of high at both ends and low in the middle,and the salt accumulation phenomenon at the top of the simulated ground pole test block was serious.Due to the large surface tension value of Na Cl,the electrical conductivity increment at the top of the simulated ground pole test block with high Na Cl solute content was also large.The capillary front is mainly enriched with chlorine salts and the capillary front is mainly enriched with sulfate.The migration speed of mixed salt solution is faster than that of distilled water,and it is easier to cause salinization disease in the test block.3)In the capillary salt transport experiment with different concentrations of salt solution as capillary transport solution: in the capillary salt transport experiment with relatively high concentrations of salt solution as the transport solution,water content and conductivity also showed a trend of decreasing first and then increasing with the increase of the height of the simulated ground pole test block.The migration speed of the mobile solution with a high concentration of mixed salt solution was faster than that with low concentration of mixed salt solution,and the higher the concentration of the mobile solution,the higher the conductivity of the top of the test block,the more prone to salt damage phenomenon.The capillary front and subfront of the sample are enriched crystals of chloride and sulfate,respectively.The type of simulated ground block has little effect on the migration of soluble salt.4)In the capillary water migration test,among the influencing factors on the soluble salt content at the top of the simulated ground pole test block,the order of significance was the existing salt in the test block > the different reinforcing materials in the test block;In the capillary salt transport experiment with different salt solutions as capillary transport solutions,the order of influence degree of the soluble salt content at the top of the simulated ground pole test block is the type of migration solution > salt in the test block > different reinforcing materials in the test block;In the capillary salt transport experiment with different concentrations of salt solutions as capillary migration solutions,the significant degree of influence factors on the soluble salt content at the top of the simulated ground support test block is the concentration of salt solution > the existing salt in the test block > the type of reinforcement material in the test block.5)In capillary water migration test and capillary salt transport test,the total amount of soluble salt at the top of each simulated ground layer test block was ranked as undesalted coarse mud test block > undesalted fine mud test block > desalted coarse mud test block >desalted fine mud test block.(2)The results of the screening of commonly used mural reinforcement materials show that:1)Disease simulation test(1)According to the curve of mass and height change of the test block,the mass and height of the test block are increasing,indicating that each disease simulation test will cause accumulation of salt and expansion of the test block.(2)According to the number of cycles and the failure of the test block when it is completely destroyed,the optimal solid content of each reinforcement material is all 4%,and the reinforcement effect of the reinforcement material under the condition of higher solid content is generally better than that under the condition of low solid content.The order of good reinforcement effect of each reinforcement material is PVAc > pure acrylic emulsion >silico acrylic emulsion > PB72.(3)The analysis of the test block extract after the fifth disease simulation shows that the order of conductivity,Cion and cion,and total soluble salt at the top of each test block is the test block strengthened by PB72 > the test block strengthened by silicone acrylic emulsion >the test block strengthened by pure acrylic emulsion > the blank test block > the test block strengthened by PVAc,which is just opposite to the order of reinforcement effect.Anion migration rate > cation migration rate.2)The effect test of reinforcement materials on the properties of the ground layer(1)From the water salt migration test,it can be seen that the total amount of conductivity,anion and cation,and soluble salt at the top of each simulated ground battle test block is the largest after PB72 reinforcement,followed by the test block after silicone acrylic lotion reinforcement,the test block after pure acrylic lotion reinforcement,the test block after PVAc reinforcement,and the empty white test block,and the smallest is the test block after PVAc reinforcement,which shows that the reinforcement effect of PVAc on the test block is significantly better than other reinforcement materials,PB72 will cause a large amount of salt accumulation on the top of the test block,which will make the reinforcement material invalid,and finally cause salt damage to the mural.(2)It can be seen from the porosity test that the porosity of the test block after PVAc reinforcement is the closest to that of the blank test block,while the porosity of the test block after PB72 reinforcement is the farthest from that of the blank test block,indicating that the nature of the PVAc reinforcement test block is the closest to the nature of the cultural relics,and follows the minimum intervention principle of mural painting protection.(3)It can be seen from the disease simulation cycle test that the weathering times of the test block strengthened by PVAc are the largest,and it is also the only strengthened test block that exceeds the blank test block.The weathering times of the test blocks strengthened by other reinforcement materials do not exceed the blank test block,indicating that PVAc has the longest protection time and the best performance for the test block.(4)From the permeability test and moisture absorption test,it can be seen that the permeability and moisture absorption rate of each test block are ranked from large to small as blank test block>test block after PVAc reinforcement>test block after pure acrylic lotion reinforcement>test block after silicone acrylic lotion reinforcement>test block after PB72 reinforcement.The PVAc reinforcement test block has the smallest impact on the body of cultural relics.(5)In a word,PVAc has the best reinforcement effect,which is closest to the cultural relics,while PB72 has the worst reinforcement effect. |
