Mechanisms Of Secondary Diseases Of Polychrome Cultural Heritages And Failure Of Typical Conservation Materials

There are many polychrome cultural relics in China.Much works has been done,such as rescuing consolidation,revelation of deterioration mechanisms,normalizing conservation materials and techniques,evaluating consolidation effect.However,the failure mechanisms of conservation materials remains obscured.Protectiv,e damages happen occasionally.This hampers the development of heritage conservation science.Four aspects of studies have been conducted to reveal the mechanisms of secondary diseases and protective damage,including sampling survey of pottery polychrome relics in Shandong province,disease mechanism based on layered structures,failure kinetics of conservation materials and the effects of conservation materials on salt migration.A survey of secondary diseases on polychrome potteries was conducted.To survey the current situation of the relics,and understand diseases reappearance mechanisms,an investigation in Qingzhou and Linzi,Shandong province was conducted.Polychrome pottery diseases,such as flaking,cracking,salt crystallization,disruption,microorganism damage,etc.were investigated.Influences of preservation environments,restoration technics and preparation layers were also discussed.Survey conclusions showed that physical factors have caused secondary diseases.A mechanism of polychrome diseases based on their layered structures was proposed.Different layers in the wall-paintings have different expansion properties and will cause stress between the layers when environmental conditions changed.This will cause damage.Quantitative experiments have been performed and showed that moisture expansion caused much more interlayer difference than thermal expansion.This mechanism has presented new tasks in screening conservation materials.The kinetics of the failure of organic adhesives and coatings was studied.Slice samples prepared from silica sand and polymers used in relic conservation were designed to undergo thermally-and UV-accelerated oxidative ageing in air to investigate the failure kinetics of these polymers.Gravimetric,water contact angle,and strength changes were tested and analyzed using curve-fitting.Time-temperature superpositions constructed from these tests and thermal shift factors were shown to follow Arrhenius scaling in both ageing protocols,though FTIR spectra tests did not show obvious changes in thermal ageing.This suggests the applicability of the Arrhenius equation in these failure processes,which were affected by both chemical and physical factors,which will be useful not only in heritage preservation.The effects of conservation materials on salt transportation in consolidated polychrome heritages were studied.Improper preservation materials may intensify salt enrichment and result in preservation damage.In this study,simulating samples of Dunhuang grotto murals were restored by five typical relic preservation materials and weathering tests were conducted.Durability of restored samples indicated that synthetic polymers with better hydrophilicity had better performance.This phenomenon was explained by analyzing the porosity and saline permeability of the samples.In conclusion,for the development of the failure mechanisms of heritage conservation materials,a survey of secondary diseases was conducted,a mechanism based on layered structures was proposed,the kinetics of adhesive failure was studied and the effect of consolidates on salt migration was studied,respectively.These exploring works presented here provide new insights for understanding the failure of heritage conservation materials and its related methodologies.