Pink discoloration on frescoes from Hurezi Monastery, Romania

A multianalitical approach based on optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction, grain size distribution and microbiological methods has been applied to characterize pink discoloration on the surface of both original painting and lime-mortar infillings of the frescoes of the refectory from the Hurezi Monastery, Romania. Polarized microscopy, the study of the cross-sections, X-ray diffraction and grain size distribution pointed out the characteristics of materials and led to a better analysis of composition and the availability to be colonized. Thick layers of bacteria developed around and into enlarged pores led to the alteration of substrate pore sizes and changes of moisture circulation. Acting simultaneously with efflorescences, disaggregation and fragmentation of the mortar and pictorial layer take place. Microbial origin of pink discoloration detected by OM and SEM was confirmed by culture based methods. The present study points out the analytical methods for identification of pink aesthetical damage of mural painting and its biological origin.