XPS Monitoring of Calcarenite Building Walls Long Exposed Outdoors: Estimation of Deterioration Trend from the Time Sequence of Curve-Fitted Spectra and PCA Exploration of the Large Dataset

Response to Reviewer 1Comments

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding crossed test and

corrections highlighted in the re-submitted files: REV-applsci-3654609

Point-by-point response

Comments 1: The paper is very interesting. My main point is around the sampling methodology. My understanding is you scrape the surface, collect the powder (and small pieces), then attach to copper tape and do XPS. Whilst XPS will analyse very surface of sample (a figure for estimated/approximate information depth would be useful), presumably the powder can have rotated when being sampled, so your analysis could from the original surface of the block or however deep your sample is within (1 or 2mm, but much greater than XPS information depth)? This need discussion within the text, and if I have understood correctly an estimated or measured depth for this sample removal, which presumably depends on state of the surface.

Response 1: We sincerely thank the reviewer to appreciate the paper andfor highlighting this fundamental aspect of the XPS procedure.

The manuscript is now revised adding paragraphs in Materials and methods (the section starting from line 180) to better clarify acquisition modalities and particularly the mounting of powdered samples following the ISO committee procedures.

‘We didn’t rotate the samples that were all acquired at 90° take off angle (normal emission to maximize intensity). In these conditions, even if the light thickness of the pressed powders could not be exactly estimated, considering the large medium area and the XPS spatial resolution, we were amply satisfied of the procedure, having obtained on average the same results from powders and from (the few)small fragments of the same sampling zones,when available, thus considered both representative of the surface composition’We have notspecified in the revised manuscript what reported in this last market paragraph, thinking that could be indirectly deduced from the present version but if the reviewer thinks it should be added we are ready to do it.

Comments 2-9: Other points that require addressing;

2. You probably do not need as much detail about previous project in the introductions, you refer back to additional analyses and compare the results, which is sensible, but feel there is more detail than needed in introduction.

3. ln 53 should discuss increasing temperatures and heat waves as well and whether these will affect deterioration.

4. ln 63 Would be good to give a slightly fuller description of what calcarenite is.

5. ln 107, several of clay species have other elements beyond silica and aluminium present as well, Mg, P, should be discussed.

6. ln153 presumably you are assuming the old building had stone from this quarry, almost certainly true, but be good to flag up this assumption in text.

7. ln 187, do the two spectrometers have any difference in performance, should be noted either way

8. ln218 would be good to add a reference to the preference for PCA if one exists.

9. ln248 related text - where (underneath?)

Responses2-9

We thank the reviewer for all the helpful suggestions answered point by point hereafter:

2.. The Introduction has been revised accordingly (starting from page 63)removing the presentation of previous project details, maintaining only the essential context and relocating more technical content to later sections when appropriate

3. A sentence has been added after line 53 to include the potential effects of increasing temperatures and heat waves on stone deterioration processes.

4. A brief definition of calcarenite has been added at the beginning of the relevant paragraph (from line 69) to introduce the material discussed in the study.

5. A brief note has been added after line 130to mention clay minerals, including Mg and P in minor amounts, to a paragraph already reporting XRD and SEM/EDS analyses of calcarenite.

6. At the beginning of Materials and methods, lines 201-202, is now reported: The two buildings in calcarenite studied in this work are made of stones, sourced from the same local quarry as required by the research project [13,14], however, no formal statement could be found, unfortunately.

7. A clarifying sentence has been added at lines 274-275, asserting no significant differences in performance were found between the two spectrometers, after a long-standing verification of the acquisition modalities based on parallel acquisitions of standard compounds.

8. The reference [17] cited in Introductionis now added to line 308, however, other two references [22,23] are citedfew lines below in the same paragraph reporting on the preference for PCA.

9. Line 248, was in fact line 284, now 380 where ‘hereafter’ is now added referring to the related test below, starting from the line 384.

Comments 10-14

10. para beginning ln 423 and ln652, these are probably better in the introduction

11. lns 538 and 541 do they converge and align perfectly? I would say mainly from your results

12. ln668 please give a reference to the ICOMOS guideline mentioned.

13. para beginning ln 670, is this recap really needed, not what I'd expect in a conclusion 

14. ln 695 two buildings?

Responses 10-14

We sincerelythank the reviewer once more for the following last suggestions, all well accepted except one (moving one paragraph from Discussion) for the justification reported in the following response, hoping that can be agreed!

10. The paragraph beginning with line 423 was moved in the Introductionassuggested while the other (likely starting at line 650) referring to previous results and ‘connected’ with the successive paragraphsreporting on the present results and on how nowadays the biofilms are treated depending on the real situations, was left in Discussion. We really hope the reviewer considers this decision acceptable.

11. We rephrased the sentences to make clearer that the phrases including ‘convergence’ refer to our results

12.  The website for the ICOMOS guide line easily downloadable is now included in the text where ICOMOS was mentioned (line 784)

13. The mentioned paragraph beginnings the Conclusion has been shortened to provide only a concise summary of the study’s timeframe and objectives, without repeating methodological details.

14. We have removed the redundant “two buildings” at line 815 of the version with revisions

Responses to Reviewer 2Comments

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisionscrossed test and

Corrections highlighted in the re-submitted files: REV-applsci-3654609

Point-by-point response

The authors employed XPS to monitor the surface of calcarenite building walls that interacted with atmospheric agents and biotic/abiotic pollutants to analyze the degradation processes of calcarenitic stones, supported by Principal Component Analysis (PCA). The followingcommentsneed to be addressed:

1. No references are cited in the paragraph between lines 48 - 57.

1. For PCA, there is no plot of the principal component and explained variance. 

1. Line 240 should be Fig. 3 instead of Figs3. 

1. It is confusing to use 3N, 3E, etc. as the sample names in Table 3. It is recommended to add a description for each sample. 

1. There is no classification about the choice of 52 months as the upper bound.

EDS results are recommended to be included in the main context instead of supplementary. 

Responses1-6

We thank the reviewer for all the helpful suggestionsand very important observationsanswered point by point hereafter:

1.      References [1-3,6] regarding the impact of abiotic and biotic factors on stone degradation (line 58) and references regarding observations and extrapolation of deterioration trends [4,5] are added to support the paragraph(lines 49–62).

2.      We have added the scree plot, which reports the percentage of variance explained by each principal component to Figure 7 now properly modified in numbering and caption (line 659).As evident, the first two components collect most of the explained variance, so the score plot and the loading plot were created taking into account only PC1 and PC2. In addition, a clarifying sentence has been inserted into the main text (line 667) to indicate the availability of this plot and its role in supporting the selection of PC1 and PC2 for further analysis.

3.      Typo in abbreviation of Figure 3 now corrected

4.      A clarifying note has been added below Table 3 to explain the sample labelling.

5.      The choice of a 52-month upper bound has been clarified in the Materials and methods section(lines 211-214): it completes the five-year monitoring period, long enough to capture both the initial degradation changesand the final convergence of surface composition.

6.      EDS results are recommended to be included in the main context instead of supplementary.

We are truly sorry that we cannot accommodate this request which we fully understand and would like to support. As also indicated in the cover letter to the Editor(s), this work was set up on XPS monitoring with PCA support only, and previous results were simply recalled if already published or partly reported in the supplementary materials if not published (as some parts of the PhD thesis). In any case they were reported to complement XPS analysis and achieve a more accurate view of the calcarenite degradation, as widely reported in the manuscript. Of course it would be hoped to have equal visibility for both the main and supplementary work and we rely on the opinion of this reviewer and the Editors

Responses to Reviewer 3Comments

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding crossed test and

corrections highlighted in the re-submitted files: REV-applsci-3654609

Point-by-point response

GENERAL REMARKS

Although the manuscript contains a series of paragraphs that are more difficult to follow due to long sentences, the editing style used shows that it is based on a long “layering” of information, through experience. The ideas are sufficiently supported by experimental data and explanations, and the research is correctly contextualized and justified.

Attention should be paid to minor editing corrections, especially to the way chemical formulas are written.

We are really grateful to the reviewer for the general remarks and observations.

A re- reading of the manuscript was first done tocorrect minor editing issues, with particular attention to the proper formatting of chemical formulas (changes highlighted in red).

INTRODUCTION

Rows 41 – 42: “implementation” sounds confusing; please use another term, such as “end of construction” or similar,

We have substituted “implementation” with “construction” lines 41-42

Rows 46 – 47: I think, it is also related to “the way the construction element was shaped” and “previous maintenance treatments”

The new sentence: ‘the modelling of the construction elements and any previous maintenance treatments’ is added at lines 44-45

Row 98: I think is rather CO2 instead of CO

We have checked the ARPAB list of air pollutants in the PhD thesis and we confirm that it was CO to be reported (also in previous work)

Row 102: petrographic, in one word

Done at line 126, thank you.

At the end, another similar works on XPS analyses may be mentioned within this chapter

As suggested by the reviewer, we have added at line 154, thenew reference [16], which is this year’s review, as a relevant example of a multi analytical application, including XPS, in heritage diagnostics.

MATERIALS AND METHODS

Figure 2: Please, add a distinct quotation a, b, c, d on each sub-figure.

Labels (a), (b), (c), and (d) have been added to the respective sub-figures in Figure 2 for clarity

After Figure 2 and before the description of method, a general defintion of XPS technique and its advantages and disadvantaegs related to other techniques must be added.

As suggested by the reviewer, a general definition, as a brief overview, of the XPS technique along with its advantages and disadvantages compared to other spectroscopic and microscopic techniques relevant to this work has been added after Figure 2, before the methodological description. Moreover, another reference [18] with a more detailed description of these and other related techniques was added at the end of the brief overview, line 265.

RESULTS AND DISCUSSION

Figure 4: For Ca2+: after 11.5 an another 5 appeared; please explain in the legend or delete from pie chart

The Ca²⁺ value originally shown as “11.5” followed by the subscript has been corrected and properly rounded to “11.6%” in the revised pie chart to ensure clarity.

Figure 4 refer to new building; please specify within caption

The caption of Figure 4 has been revised to clearly indicate it refers to the reference sample from the new calcarenite building.

Row 592: Please, replace “excursions” with an another word

The word “excursions” has been replaced with “variations” at line 709

CONCLUSIONS

No observation