Identification of secondary salts and their sources in deteriorated stone monuments using micro‐Raman spectroscopy, SEM‐EDS and XRD

Abstract

Salts crystallisation is a cause of deterioration of stone monuments. Very small sizes of salt crystals, often a multiphase composition and usually low concentrations hamper their identification. Therefore, micro‐Raman spectroscopy, scanning electron microscopy and, in some cases, X‐ray diffraction have been used to identify the salts that crystallised within and on the weathered limestone and sandstone architectonic details of the Blessed Salomea sculpture and its arch in the cloister of the Poor Clares in Kraków, Poland. Possible sources of salts, i.e. regarding the plaster around the details, the mortar of joints of the arch and previous conservation procedures, have been discussed. The limestone sculpture reveals the presence of black crusts and the sandstone arch of white efflorescences, both stones crumble and exfoliate. Gypsum and barite were the only salts in the black crust and subflorescences of the limestone. The salts in the pore space of the sandstone include mainly aphthitalite, niter, nitratine and burkeite, while efflorescences consist of thenardite and syngenite. Such differences probably result from various precipitation conditions in narrow pore spaces and on the unconfined sandstone surface. The deterioration products have been mainly assigned to air pollution, stone itself in the case of the limestone, and migration of ions from structural elements of the arch in the case of the sandstone. The impact of the chemicals utilised for stone conservation also seems to be possible. Characterisation of the salts present in deteriorated stones can help in selecting the methods of stone desalination and conservation. Copyright © 2016 John Wiley & Sons, Ltd.

Mineralogical and geochemical studies of secondary mineral assemblages related to deterioration of building materials

“…How ever, they did not give any clue as to their hydration state. To cor rob o rate the au thors' sup po sitions based on the SEM-EDS re sults, the iden ti fi ca tions had to be crosschecked us ing the XRPD and Raman microspectroscopy re sults (Marsza³ek, 2016). These meth ods have been also used to an a lyze salt efflorescences found on the bor der be tween the lime stone blocks and the ce ment mor tar in some places of the foun da tions of the Myszkowskis Cha pel.…”

“…There fore, the pore-size dis tri bu tion of build ing ma terial is very im por tant in the de te ri o ra tion pro cesses (Ro driguez-Navarro and Doehme, 1999;Benavente, 2011). The chem i cal com po si tion of sec ond ary salts de pends in gen eral on nat u ral and anthropo genic, in ter nal and ex ter nal fac tors (Manecki et al, 1997;Marsza³ek, 2016). They in clude, in par tic -u lar, com po si tion of sub stra tum, cli ma tic and top o graphic condi tions, an i mal and mi cro or gan ism ac tiv i ties, cap il lary rise of ground and soil wa ters, pol lu tion of the at mo sphere, as well as chem i cals used for con ser va tion pro cesses.…”

Recent advances in linear and non‐linear Raman spectroscopy. Part XI

“…Marszalek reported on the identification of secondary salts and their sources in deteriorated stone monuments using micro‐Raman spectroscopy, SEM‐EDS, and XRD. They find that the characterization of the salts present in deteriorated stones can help in selecting the methods of stone desalination and conservation . Sevcik and co‐workers used micro‐Raman spectroscopy to investigate the carbonation reaction in a lime paste produced with a traditional technology.…”

“…They find that the characterization of the salts present in deteriorated stones can help in selecting the methods of stone desalination and conservation. [123] Sevcik and co-workers used micro-Raman spectroscopy to investigate the carbonation reaction in a lime paste produced with a traditional technology. The results of their approach have been compared with those obtained from quantitative phase analysis with X-rays powder diffraction and allow for a highly accurate description of the carbonation process in traditional lime-based systems.…”

Applications of Raman spectroscopy in art and archaeology

“…Casanova Municchia et al [15] studied the mineralogical and chemical composition of the patina using a multianalytical approach to characterize the alteration products. Analyses performed both on single fragments and on polished cross sections collected from all four temple facades and from one area in the temple interior showed the systematic presence of manganese mineral phases: hollandite (Ba(Mn 4 + 6 Mn 3+ 2 )O 16 ), romanechite ((Ba,H 2 O) 2 (Mn +4 ,Mn +3 ) 5 O 10 ) and manganite (MnO(OH)). These black neominerals are precipitated in the surface of non-leachable areas of the monument from dissolved Mn(II), naturally leached from the laterite bricks during the variations of wet and dry seasons and transported by rainfall to the protected areas of the facades.…”