Rare Biogeochemical Phenomenon Associated to Manganese Patinas on Mural Painting and Granite Ashlars
Round 1
Reviewer 1 Report
Authors have studied the source of the Mn Patina that is formed on the mural paintings in the Church of Sta. Marina north of Portugal. They carefully eliminate the possible sources by using the techniques like optical microscopy, XRD, micro Raman, XPS, SEM and ICP-MS.
In the study first, they have identified the original (?) pigments used in the mural paintings during two campaigns separated by a century. Then they have carried out the experiments to identify the composition of the building materials such as stones and mortars. The original building materials (mainly the granites and phyllites) were found to be the main source of Mn and the patina is formed with the help of the biological growth that has been observed in SEM images. However, the identification of the biological growth yet to be done.
Authors mentioned also the existence of the cement repairs in their discussion as a potential reason for the water migration which is a reasonable deduction. It would be good to add some information on these repairs (i.e., when the cement was introduced to the building and with what extent). It could be added to the supplement document in the part where the building is explained briefly. Although authors talk about the physical impact of cement (different water and water vapor permeability than the original mortars) it also could be potential source of salt especially if any kind of sea sand and/or sea water had been used in the cement mortar process.
Another question is of course if there is an intervention in the building have the mural paintings been touched (by means of repairs and/or conservation)?.
Best,
For the stone weathering types please also check and include in the references the ISCS Illustrated Glossary of Stone Deterioration Patterns athttp://iscs.icomos.org/pdf-files/Portuguese_glossary.pdf
Author Response
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Author Response File: Author Response.docx
Reviewer 2 Report
Comments and suggestion for authors are presented in attached file.
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.docx