Effect to the Copper System Pigments by the Nitrogen Dioxide(NO₂) Gas

Abstract

Malachite and Azurite are the typical copper system pigments which used the mural paintings since ancient times. The mural painting is at risk for damages of the painting layer by atmosphere gas because it is exposed at external environment. In this study, it did experiment about an effect to Malachite and Azurite by environmental pollution gas(NO2, CO2, SO2) then analysis and estimate about test for pieces using mural painting colored that two pigments. As a result, Malachite and Azurite were changed on NO2 but not changed CO2 and SO2. Especially as the concentration of NO2 is increased, exfoliation of the pigment layer weave remarkably formed pores on the pigment particles on SEM, the phenomenon to be pieces were observed together with smaller particles. In the case of Malachite that were exposed to NO2 gas, new compounds(Rouaite : dicopper (nitrate(V) trihydroxide, Cu2(NO3)(OH)3)) was appeared by XRD analysis. Therefore, there had been able to verify the fact that the cause exfoliation and discoloration phenomena accompanied by chemical changes for Malachite and Azurite.