Multi-Technique Approach for the Sustainable Characterisation and the Digital Documentation of Painted Surfaces in the Hypogeum Environment of the Priscilla Catacombs in Rome

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Comments for author File: Comments.pdf

Comments on the Quality of English Language

English should be improved.

Author Response

Authors’ response:

The authors wish to thank the reviewers for their comments.

The manuscript has been revised according to the reviewers’ suggestions, and it has been enriched with several major changes and data additions, critical discussion of results with extensive comparisons. The delay of submission allowed the authors to provide deeper data analyses in order to accomplish a more complete discussion and integration of the results, as requested by the reviewers.

 

 

General remark about the paper: Could the authors elaborate on why they believe their approach is more sustainable compared to more common methods aimed at hypogea preservation? The term “sustainable” is frequently used, and it would be helpful if the authors could clarify the specific sustainable features of their protocol and explain the reasons behind their claims. Since “sustainability” can encompass various meanings and objectives, it is important to better clarify this aspect to align the paper with the journal’s scope.

Authors’ response: the “sustainable” features of the work has been highlighted in several parts, mainly in introduction and conclusions, also following some points of the Special Issue vision.

 

• Lines 115-123: This section could potentially be omitted for brevity and clarity.

Authors’ responses: the section has been reduced and rephrased.

• Line 149: Please add a reference, as currently only brackets are present.

Authors’ responses: the reference [21] has been added.

• Line 183: It would be clearer to refer to figures as “…Area A1(Figure 8a)”. Kindly remove “,evidenced in the figure 8a)”.

Authors’ responses: the sentence has been rephrased as suggested.

 

• Line 193: A colon should be placed after “colour”: and the comma should be removed.

Authors’ responses: element added.

 

• Line 198: Please specify that the NMR signal is proportional to 1H (Proton), thus making it easily linked to the presence of water.

Authors’ responses: this concept was explained in the text and the reference of paper where the proportionality between water content and NMR signal is reported. A sentence has been rephrased and added at the beginning of paragraph 3.2 (Lines 190-193)

 

• Lines 265-274: Indicate that fluorescence is emitted by the superficial material, and

therefore, this technique cannot be used to study what lies beneath.

Authors’ responses: in order to address the reviewer comment, this feature has been highlighted in the text (lines 290-296) and a short explanation has been given.

 

• Line 356: Please clarify which technique requires excess energy to achieve the same goal.

Authors’ responses: the sentence has been removed because not coherent with the text.

 

• Lines 405-407: Have you identified the actual reason? Are there water infiltrations?

Authors’ responses: The catacombs of Priscilla are located below the road level and the above embankment is rich in vegetation that with rains can be a vehicle for water infiltration (geographic coordinates 41°55'51"N 12°30'29"E). The variations of the humidity content, revealed by the NMR, ranging from 12% to 20%, may be attributed to infiltration caused by the vegetation above the catacombs. This element has been added to the text (lines 132-138). Further insight into this complex topic, regarding the specific identification of water sources within such a complex site, is beyond the scope of the present work.

 

• Lines 444-463: This section should be moved to the “Materials and Methods” section.

Lines 473-483: This part should also be moved to the “Materials and Methods” section. Lines 528-541: This part should be moved to the “Materials and Methods” section.

Lines 511-525: This section belongs in the “Materials and Methods” section.

Authors’ responses: the sections have been moved in section “3.Methods”

 

• Lines 563-565: These considerations should be included in the “Discussion” section.

Authors’ responses: the text has been moved to enrich the “Discussion” section.

 

• Conclusions: The conclusions seem to reiterate the points made in the “results” section, which also requires improvement as much of the content needs to be moved to the “Materials and Methods” section. The conclusions should provide a more comprehensive synthesis of the findings.

Authors’ responses: the conclusion has been synthetized, providing hypotheses on the discussed results and prospective for future research.

 

Discussion section: why there is not a “discussion” section? I think it’s fundamental to add one. As it currently stands, the article appears to be a case study rather than research suitable for publication in Sustainability. This is due to the lack of fulfilment of actual sustainability goals and the absence of innovation in the field. To enhance its suitability for publication, the article would benefit from including a “discussion” section where the authors explain the impact of their research on the field (e.g., the combined use of unconventional techniques, the reasons for recommending these specific techniques, the advantages their combined use can bring, and how this was demonstrated in your work).

Authors’ responses: the “discussion” section has been added to integrate the findings from the different methodologies, attempting innovative ways of data-fusion in order to highlight their complementary information. This allows a better understanding of the significance of the outcomes.

 

 

Final general remarks:

At present, the paper comprises a series of considerations that are not connected to real elements (for example, the mention of possible infiltrations in areas A1 and B1 seems to be an assumption without supporting evidence). Additionally, it is not clear how your work contributes to the improved conservation of the hypogeum. If you have used various techniques to highlight areas with higher moisture that varies seasonally, I believe it is not enough for publication. It would be beneficial to explain how this information will facilitate appropriate conservation measures (e.g., what measures do you recommend?). Clarifying the types of precautionary measures needed to enhance the conservation conditions of the hypogeum will underscore the importance and necessity of using these techniques.

It is clear that substantial fieldwork has been conducted. However, both Results and Conclusions need to be more robust to support an article worthy of publication in this journal, especially considering that some content from the “results” section should be moved to “materials and methods”. I encourage the authors to reconsider the article by focusing on the motivations for combining the various techniques, the concrete advantages of this protocol compared to other approaches (rather than discussing sustainability in general terms). By doing so, the article would better align with the journal’s objectives and provide a stronger contribution to the field.

Authors’ responses: results, discussion and conclusions have been revised in order to better contextualize the contributions and the motivations of the presented work.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The article includes a description of a number of non-destructive techniques for the study of the conservation conditions and possible moisture problems in hypogeum environments. However, their usefulness has not been sufficiently demonstrated. Although the application of these techniques can be potentially interesting, their use is complex and time-consuming and is not justified as the authors do not demonstrate that they have been able to extract information of interest that could not be obtained by organoleptic examination. Only the detection of anomalous moisture levels could justify the use of NMR together with IR thermography, but in this case they have not been done at the same time, so the results would not be useful to diagnose possible future preservation problems.

The authors did not explain on what criteria the measurement areas were chosen and if any additional alterations were observed on those areas prior to their selection. 

In the discussion of the results obtained by IR thermography, it is stated that in the analysis area C1, there is an area that has undergone a previous restoration in the upper part and some areas with detachment in the central part, however, from the acoustic images, previous restorations in other different areas are identified. 

Only the use of NMR would be justified to observe differences in the water content that can be related to possible conservation issues, but in the shown images the variations are not large and the trends seem to be different in area C1 than in A1 and B1. In areas A and B it is said that the humidity decreases in March 23rd compared to July 22nd due to water infiltration from aquifers, would these aquifers have dried up? Perhaps it would be necessary to make more measurements over time to see these trends.

An extensive description of the LIF measurements and data treatment, but they don’t seem to give any results. The absence of chlorophyll, presence of calcite and areas with detachment must be discussed.

Author Response

Reviewer #2

 

Authors’ general comments:

The authors wish to thank the reviewers for their comments.

The manuscript has been revised according to the reviewers’ suggestions, and it has been enriched with several major changes and data additions, critical discussion of results with extensive comparisons. The delay of submission allowed the authors to provide deeper data analyses in order to accomplish a more complete discussion and integration of the results, as requested by the reviewers.

 

The article includes a description of a number of non-destructive techniques for the study of the conservation conditions and possible moisture problems in hypogeum environments. However, their usefulness has not been sufficiently demonstrated. Although the application of these techniques can be potentially interesting, their use is complex and time-consuming and is not justified as the authors do not demonstrate that they have been able to extract information of interest that could not be obtained by organoleptic examination. Only the detection of anomalous moisture levels could justify the use of NMR together with IR thermography, but in this case, they have not been done at the same time, so the results would not be useful to diagnose possible future preservation problems.
The authors did not explain on what criteria the measurement areas were chosen and if any additional alterations were observed on those areas prior to their selection. 

Authors’ responses: In principle, all the imaging techniques applied in the heritage site offer wide surface mapping, while the investigations were restricted to some representative areas, in the proximity of some lacunas where severe loss of the painted scene were already occurred. This helped the evaluation of the effectiveness of restauration interventions after some decades. Results, discussion and conclusions have been revised in order to better contextualize the contributions and the motivations of the presented work.

 

In the discussion of the results obtained by IR thermography, it is stated that in the analysis area C1, there is an area that has undergone a previous restoration in the upper part and some areas with detachment in the central part, however, from the acoustic images, previous restorations in other different areas are identified. 

Only the use of NMR would be justified to observe differences in the water content that can be related to possible conservation issues, but in the shown images the variations are not large and the trends seem to be different in area C1 than in A1 and B1. In areas A and B it is said that the humidity decreases in March 23rd compared to July 22nd due to water infiltration from aquifers, would these aquifers have dried up? Perhaps it would be necessary to make more measurements over time to see these trends.

Authors’ responses: The aim of the project was not to monitor the water content over time. NMR measurements highlight the water content in two different moments of the year and they were used as support to other techniques in this multidisciplinary approach. Although two measuring campaigns cannot represent a full dynamics of water migration that should require long-term monitoring, the NMR results clearly suggest a non-steady state. Results have been compared and discussed in a deeper way, also in relation with the previous restored areas.

 

 

An extensive description of the LIF measurements and data treatment, but they don’t seem to give any results. The absence of chlorophyll, presence of calcite and areas with detachment must be discussed.

Authors’ responses: after the reviewer comments, the LIF part has been strongly revised after deeper data analysis, especially comparing it with the other techniques (see par.4.4 lines 511-598).

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The article is highly relevant to the field of cultural heritage conservation, especially for the use of advanced technologies in a delicate hypogeum context like the Priscilla catacombs. The multi-technique and non-destructive approach represents a significant and innovative contribution.

The methodology is well described, and the combined use of advanced technologies such as NMR, AF-AI, LIF, IRT, and RGB-ITR is appropriate for the study and conservation of painted surfaces in the catacombs. However, a more detailed description of how each technology was specifically applied could improve readers' understanding.

The article is written clearly and coherently, with well-structured sections. However, It might be interesting to add a graphic image to the "methodology section" that explains all the steps taken in the paper.

The data presented are detailed, and the analysis is thorough. The integration of different imaging techniques and cross-referencing the collected data are well executed. Including visual examples of the results obtained for each applied technique would be useful.

The conclusions are well supported by the results and clearly demonstrate the effectiveness of the multi-technique and sustainable approach. The authors adequately acknowledge the limitations of their study and suggest directions for future research.

Author Response

The article is highly relevant to the field of cultural heritage conservation, especially for the use of advanced technologies in a delicate hypogeum context like the Priscilla catacombs. The multi-technique and non-destructive approach represents a significant and innovative contribution.

The methodology is well described, and the combined use of advanced technologies such as NMR, AF-AI, LIF, IRT, and RGB-ITR is appropriate for the study and conservation of painted surfaces in the catacombs. However, a more detailed description of how each technology was specifically applied could improve readers' understanding.

 

Authors’ responses: The authors wish to thank the reviewers for their comments.

 

 

The article is written clearly and coherently, with well-structured sections. However, It might be interesting to add a graphic image to the "methodology section" that explains all the steps taken in the paper.

Authors’ responses: in order to address the reviewer comment, two images were added to the article that explain the workflow and to sum up the analyses performed within the chapel (Figure18a and 22).

 

The data presented are detailed, and the analysis is thorough. The integration of different imaging techniques and cross-referencing the collected data are well executed. Including visual examples of the results obtained for each applied technique would be useful.

Authors’ responses: The manuscript has been revised according to the reviewers’ suggestions, and it has been enriched with several major changes and data additions, critical discussion of results with extensive comparisons and several additional details on the employment of the technologies within the site (see figures 19-21).

 

 

The conclusions are well supported by the results and clearly demonstrate the effectiveness of the multi-technique and sustainable approach. The authors adequately acknowledge the limitations of their study and suggest directions for future research.

 

 

Reviewer 4 Report

Comments and Suggestions for Authors

Some comments and typos are listed in the attached pdf.

Comments for author File: Comments.pdf

Author Response

The article is comprehensive, well accompanied by bibliographical references and an analysis of the data and materials collected. The strong interdisciplinary nature entails considerable problems of holistic data integration and analysis, which are skilfully resolved in the project through the use of a 3D textured model as the basis of a developing information system. The structure of the paper is well articulated and comprehensive. Although the techniques used are very specific, they are well described in both methodology and results.

 

The introduction should briefly explain the reasons for choosing those specific samples for detailed analysis (e.g. preliminary visual analysis of ongoing degradation phenomena, importance of the pictorial apparatus, vertical and more accessible positioning, etc.).

Authors’ responses: the introduction has been improved.

 

Line 431 refers to the most recent restoration work but does not say when it was carried out or what it consisted of.

Authors’ responses: unfortunately, deeper research on previous restoration works didn’t provide specific details about timing and materials, so the authors preferred to generally cite them (see lines 478-478)

 

The images are consistent with the writing. Some may be larger, but this is probably due to layout requirements. Figure 16 should be replaced with a higher definition one.

Authors’ responses: all the figures have been controlled and replaced where necessary.

 

The bibliography is extensive, with respect to the specific topic, and each part of the text is well justified with references. In the reference list, some references have cited all the authors’ names, while others omit them with the words “et al.”.

Authors’ responses: the references have been properly modified.

 

 

Some typos are listed here:

- Line 125: please, write the full form of ITR;

- Line 126: briefly reference the ENEA (Agenzia nazionale per le nuove tecnologie…)

- Line 149: brackets;

Authors’ responses: the typos have been corrected.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors addresed all the comments.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have significantly improved the article and addressed all the points raised in the revision. I agree with the publication of the manuscript as it is