Review Reports - Three-Dimensional Digital Reconstruction and Archaeometric Approaches for Hydroxyapatite-Based Restoration of Sacidava Roman Fortress

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript addresses an interesting and timely topic combining digital heritage documentation, archaeometric characterization, and nanomaterial-based conservation for the Sacidava Roman fortress. The integration of 3D reconstruction and hydroxyapatite treatment demonstrates innovation and clear applicability to heritage preservation. The scientific value is high, and the paper fits well within the scope of Coatings. However, some improvements are recommended before acceptance.

While the experimental workflow is generally comprehensive, please provide more detail on sample selection criteria and the replication of measurements (especially for AFM and SEM analyses). Specify the number of samples per tower and the statistical treatment of data.
The Fusion 360 reconstruction is well described, but a schematic workflow figure would enhance readability. Clarify the accuracy of spatial scaling and error estimation between drone, satellite, and historical sources.
Several figures contain dense text or are of relatively low contrast. Please ensure high-resolution images and uniform color scales for consistency across SEM, AFM, and CT visualizations.
The Principal Component Analysis and dendrogram are informative, but explain the variance percentage accounted for by PC1 and PC2, and how these link to environmental parameters (humidity, pH, salts).
In conclusions section, consider summarizing the main findings in bulleted form to highlight the scientific and practical contributions, especially the effect of HAp treatment on roughness reduction and pore sealing.

Comments on the Quality of English Language

The English is comprehensible but needs moderate editing for grammar, tense consistency, and flow. Simplifying long sentences will make the paper more accessible to an international audience.

Author Response

Dear Reviewer,

Answer: Thank you very much for your appreciations and for clarity evaluation.

While the experimental workflow is generally comprehensive, please provide more detail on sample selection criteria and the replication of measurements (especially for AFM and SEM analyses). Specify the number of samples per tower and the statistical treatment of data.

Answer: For answering at your request, we inserted a short sub-chapter „Sample selection, replication, and statistics„, at Experimental Part, at sub-chapter Equipment.

The Fusion 360 reconstruction is well described, but a schematic workflow figure would enhance readability. Clarify the accuracy of spatial scaling and error estimation between drone, satellite, and historical sources.

Answer: We inserted a schematic workflow figure would enhance readability. Also, we clarified the accuracy of spatial scaling and error estimation between drone, satellite, and historical sources. For this purpose, we added some new figures, where we answered at your requests.

Several figures contain dense text or are of relatively low contrast. Please ensure high-resolution images and uniform color scales for consistency across SEM, AFM, and CT visualizations.

Answer: We processed the images, offering them clarity and a better resolution

The Principal Component Analysis and dendrogram are informative, but explain the variance percentage accounted for by PC1 and PC2, and how these link to environmental parameters (humidity, pH, salts).

Answer: We inserted new paragraph in the text, after the PCA diagram

In conclusions section, consider summarizing the main findings in bulleted form to highlight the scientific and practical contributions, especially the effect of HAp treatment on roughness reduction and pore sealing.

Answer: We reorganized the entire chapter Conclusions, taking into account your suggestion.

Comments on the Quality of English Language

The English is comprehensible but needs moderate editing for grammar, tense consistency, and flow. Simplifying long sentences will make the paper more accessible to an international audience.

Answer: We simplify long sentences will make the paper more accessible to an international audience.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

3D Reconstruction and Archaeometric Approaches for Hydroxyapatite-based Restoration of Sacidava Roman Fortress

The paper details an integrated study of the Sacidava Roman fortress in Romania, focusing on its degradation and preservation. The research combines a 3D digital reconstruction of the 4th-century AD fortress, created using Autodesk Fusion 360, with extensive archaeometric analysis of the ancient mortar samples. Various microscopic and analytical techniques were employed to characterise the material’s heterogeneous microstructure, revealing components like phyllosilicates and secondary reaction products. The study evaluates the efficacy of hydroxyapatite nanomaterial coatings in reducing surface roughness and sealing pores for restoration, particularly on towers severely affected by humidity and salt crystallisation from the nearby Danube River. The study correlates chromatic data and environmental factors (pH, salt concentration) with the degradation status, using statistical tools such as PCA and dendrograms to classify the condition of the fortress's towers.

The sections and subsections should be enumerated to aid comprehension of the paper hierarchy.

Line 381 'Equipments' -> Equipment. Also consider using the term 'Methods and Materials'. AFM, CLSM, SEM and the rest mentioned in this subsection are methods, not pieces of equipment. You should, of course, report on the particular equipment (e.g. model, type, etc) used, which I understand was part of the intention and is a good practice for repeatability.

Line 651 '3D reconstruction'. The most appropriate term is '3D modelling', not reconstruction. In the literature, the reconstruction term usually denotes a 3D scan or its processing. Of course, you do explain what you did in 652-655, so this comment is optional. Moreover, this 3D modelling should be near the end, because after that, you continue with further material studies.

The paper applies the methods correctly and provides a thorough documentation of the materials of the monument. However, the paper does not provide a review of relevant literature or background. This is essential to comprehend the originality of the proposed work, beyond the documentation of the particular monument.

Moreover, besides the thorough documentation that it offers, the paper does not provide a methodology for other scientists to replicate. Indeed, the study is valuable on its own as the documentation of the particular monument. However, to go beyond reporting the particular effort and provide a methodological exemplar, some guiding insights and an operational protocol should be discussed at the end of the paper.

Author Response

Dear Reviewer,

Answer: Many thanks for your nice words. A summary of the changes in the manuscript and the point-to-point responses to all the comments and suggestions are given below. We have tried our best to ensure that the answers are reasonable enough. However, if the answers don’t meet your demands, we are willing to revise the manuscript according to your comments in a further version.

The sections and subsections should be enumerated to aid comprehension of the paper hierarchy.

Answer: We did the corrections

Line 381 'Equipments' -> Equipment.

Answer: We did the correction.

Also consider using the term 'Methods and Materials'. AFM, CLSM, SEM and the rest mentioned in this subsection are methods, not pieces of equipment. You should, of course, report on the particular equipment (e.g. model, type, etc) used, which I understand was part of the intention and is a good practice for repeatability.

Answer: We changed the title of this chapter, after your suggestion, and we inserted all the details suggested by you. They are important and useful, indeed. Thank you!

Answer:

Thank you for your suggestion. We agree with your suggestion to replace in the title 3D reconstruction.

But, based on other literature reports, we suggest to replace 3D reconstruction with 3D Digital reconstruction as a multidisciplinary and interpretative process that integrates 3D modelling and reconstruction with historical, environmental, and scientific data to recreate the full context, function, and temporal evolution of cultural heritage assets.

3D Digital reconstruction combines the precision of 3D reconstruction with the interpretative depth of archaeology, science, and storytelling, creating a tridimesional model.

We took into evidence the definition of these terms, as follows:

3D Digital Reconstruction is the most comprehensive definition, because it includes both 3D Modelling and 3D Reconstruction as part of its process, it can integrate archaeometric data (e.g., SEM–EDS, CT, FTIR, so on), historical archives, weather simulations, or digital storytelling, and not in the last time, it serves multiple purposes — documentation, research, education, and public engagement — while 3D modelling or reconstruction usually focus on visualization and measurement.

We would appreciate your final decision on this last title proposal for our paper. Thank you!

Also, we excluded the comment from 652-655, which is optional, indeed.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Please see the attachment.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

The approach developed in this article is resolutely multidisciplinary, exploring several very different aspects related to the enhancement and preservation of an archaeological site, such as 3D reconstruction, the study of erosion and bio-colonization factors affecting archaeological remains, the contribution of colorimetric analysis and its correlation with physical parameters, as well as the chemical and structural analysis of mortars and the study of the influence of restoration techniques.

This approach is both very interesting and a little unsettling, as some aspects are addressed in less depth than others.

Answer: A summary of the changes in the manuscript and the point-to-point responses to all the comments and suggestions are given below. We have tried our best to ensure that the answers are reasonable enough. However, if the answers don’t meet your demands, we are willing to revise the manuscript according to your comments in a further version.

Here are a few comments on this article:

Comments on the form of the article:

The structure of the article, and in particular the “Results and Discussion” section, would be clearer if it were divided into distinct sections, each covering one of the article's objectives.

Answer: We divided the “Results and Discussion” section, in:

3D Reconstruction Material Characterisation (SEM-EDS, CLSM, AFM);

Environmental Correlation (CIELAB, PCA);

Conservation Assessment (HAp activity);

3D reconstruction with methodological reproducibility (data resolution, image overlap, software parameters).

I have to mention that this divide is suggested by another reviewer of this paper.

Certain sentences are repeated several times: lines 570-572 and 589-590: 964-967 and 979-981.

Answer: We removed the repeated phrases.

Figure 6: the colors are not explained: please, use the legend from Figure 7

Answer: They are explained at legend. E2 gate (blue), G tower (red) and C lower (green)

Table 2 is not a correlation matrix: it shows values but does not establish correlations between parameters.

Answer: The title of Table 2 has been changed. Also, in the text the corrections have been made.

Figure 8 is not commented on.

Answer: Some paragraph has been added after Figure 8, explaining its significance.

Figure 15 is insufficiently commented on.

Answer: We added new paragraphs.

Figure 21: what does each of the sub-images represent?

Answer: We reorganized the sub-images and retained only one image for every tested towers. The other sub-images have been removed.

Comments on the content of the article:

The section discussing the correlation between weathering and tower color is interesting, but the presentation of the results is not always very clear:

Answer: We rephrased this sib-chapter making it clearer.

In Figures 6 and 7, the pH and humidity values appear to be monthly averages, but over how many years where they measured?

Answer: These parameters have been monitorized 3 three years, but in this paper, we selected the data from one years (July-june).

In Table 2, what do the physical parameter values represent (monthly, annual, multi-year averages)?

Answer: the physical parameter values represent monthly for one year.

What about their variability?

Answer: We added a paragraph referring to Relative humidity, pH and humidity in this area.

Regarding the color measurements, how were they taken (spot measurements or overall measurements, at a single point or several points, etc.)?

Answer: The color measurements, how were they taken as spot measurements, in triplicate in different points.

In general, this article lacks a “methods” section indicating the conditions under which the measurements were taken.

Answer: Some new explanations have been added.

Line 621: you mention the correlation matrix: it would be interesting to present it.

Answer: We inserted a correlation matrix with the corresponding explanation. Thank you for your suggestion!

Figure 8 is interesting but is not commented on.

Answer: We added explanations accordingly.

At the end of this section, there is no explanation proposed for the variations in the physical parameters measured (distance to water, etc.).

Answer: A detailed paragraph are inserted in the paper.

The section on “3D reconstruction is the one that would benefit most from further development. In particular, explanations are needed on the transition from the partial plan (Figure 3) to the overall plan used as the basis for the reconstruction. The choice of textures to be applied should also be discussed, particularly for elements that have not been preserved: what criteria were used to apply the structures to the towers and walls? As the paper title focuses on 3D reconstruction and texture analysis, the choices made for the reconstruction proposal must be commented on and justified.

For a better understanding, towers A to G should be marked on Figure 12.

Finally, from a purely aesthetic point of view, the textures seem to have been created by copying and pasting images of existing buildings, resulting in a horizontal and vertical juxtaposition of identical iron inclusion patterns, which gives to the whole structure a rather unrealistic appearance.

Answer: For a better understanding, we marked the towers A to G on Figure 12.

The textures were not created by copying and pasting images of existing buildings, this texture is included in the soft, and it is an usual option for this soft. We did not choose the option copy-paste. We treated these results with a high responsibility and honesty.

The text does not indicate when the treatment with HAP was carried out: this is important for understanding the analysis performed.

Answer: All the measurements and treatment have been applied during the summer and monitorized in time for one year.

Figure 14, included in the “Untreated sample” section, presents examples of treated samples: please review the organization of this section.

Answer: We rephrased the figure legend in order to be clearer.

Lines 855-856, you indicate that the HAP layer preserves the “breathability” of antique mortar: have you been able to test this ability to evacuate moisture, and quantify the difference compared to untreated mortar?

Answer: We added new experiments for breathability, and Capillary Water-Absorption Coefficient (C) data have been inserted in the paper, as one of the most representative parameters fir breathability.

Figures 18 and 19 are neither cited in the text nor commented on.

Answer: Their marks in the text have been inserted.

Lines 907-911, you mention that tower A is more affected by humidity and salts than the other. Unfortunately, this result contradicts what is shown in the first part, particularly Table 2: could you comment on this point?

Answer: It was a writing error. We corrected. Thank you for your observation!

Line 983: error: 79.8% instead of 56.8%.

Answer: It was a writing error. We corrected. Thank you for your observation!

In conclusion, you indicate that your reconstruction will enable orthophotos and photogrammetry to be produced: it is the opposite; orthophotos and photogrammetry should enable 3D reconstruction.

Answer: We corrected the paragraph.

Line 1022, you mention that you were able to visualize structural transformations and vulnerable areas: which ones? You do not present this in the text.

Answer: We added in the text the structural transformations and vulnerable areas

It would also be interesting to discuss the effectiveness of HAp over time.

Answer: A complex and detailed paragraph has been added in the paper. Thank you for your suggestion.

In conclusion, your study is interesting because it addresses a wide range of aspects of building enhancement and preservation, but the analyses presented need to be refined and your conclusions need to be further justified.

Answer: After your precious suggestions, we added new experiments, new data and some text reorganization have been done. Hoping that we solved the inconsistent data.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors This is a review report for the manuscript entitled "3D RECONSTRUCTION AND ARCHAEOMETRIC APPROACHES FOR HYDROXYAPATITE-BASED RESTORATION OF SACIDAVA ROMAN FORTRESS" This manuscript presents an interdisciplinary study combining the 3D reconstruction of the Sacidava Roman fortress, its archaeometric characterisation, and research into nanomaterial-based conservation (hydroxyapatite coatings). It effectively combines digital modelling, microscopy, and environmental analyses to understand material deterioration and propose conservation methods. The subject is relevant to the journal's scope, which focuses on protective coatings, restoration materials, and surface characterisation. However, I believe that the manuscript requires extensive and large-scale revision before it can be accepted due to structural, stylistic and methodological issues. Although scientifically valuable, it needs improvement in terms of clarity, data presentation and depth of discussion. The introduction section is very long and contains excessive historical and general Roman context; is this necessary? It has been determined that it should be shortened to focus on the research gap, objectives, and innovations. The results section mixes explanations, dates, and interpretations without clear subheadings. It is thought that dividing it into sections as follows would be easier for the reader: 3D Reconstruction Material Characterisation (SEM-EDS, CLSM, AFM) Environmental Correlation (CIELAB, PCA) Conservation Assessment (HAp activity) 3D reconstruction lacks methodological reproducibility (data resolution, image overlap, software parameters). The inclusion of this information will improve the quality of the article. Improvements should be made in terms of writing and linguistics. The innovation should be clearly stated: ‘This study presents, for the first time, an archaeometric-3D reconstruction and HAp nanocoating evaluation for a Roman fortress on the banks of the Danube River.’ What is SEM EDS, AFM Analysis? Abstract too long. Keywords can be improved. Introduction is too long and very complicated. I am in lost in the paper. Please summarise abstract and intorduction , it could be very briefly what is topic, related studies, gaps and your innovation. why there is also another title with history in the section? Line 348, which samples? L123, Empire is. In Discussion section, connect findings with relevant literature Some references should be fixed or improved: [47, 58 , etc] Conclusion is also too long, present bullet-style implications and limitations for clarity. Overall, it requires revisions.

Author Response

Dear Revierwer,

First of all, we want to express our gratitude for taking your time to review our paper, for the professional comments and suggestions on our manuscript. We have revised and improved the manuscript accordingly. A summary of the changes in the manuscript and the point-to-point responses to all the comments and suggestions are given below. We have tried our best to ensure that the answers are reasonable enough. However, if the answers don’t meet your demands, we are willing to revise the manuscript according to your comments in a further version.

This is a review report for the manuscript entitled "3D RECONSTRUCTION AND ARCHAEOMETRIC APPROACHES FOR HYDROXYAPATITE-BASED RESTORATION OF SACIDAVA ROMAN FORTRESS". This manuscript presents an interdisciplinary study combining the 3D reconstruction of the Sacidava Roman fortress, its archaeometric characterisation, and research into nanomaterial-based conservation (hydroxyapatite coatings). It effectively combines digital modelling, microscopy, and environmental analyses to understand material deterioration and propose conservation methods. The subject is relevant to the journal's scope, which focuses on protective coatings, restoration materials, and surface characterisation.

Answer: Thank you for your elaborate presentation.

However, I believe that the manuscript requires extensive and large-scale revision before it can be accepted due to structural, stylistic, and methodological issues. Although scientifically valuable, it needs improvement in terms of clarity, data presentation, and depth of discussion.

Answer: We are receptive to your suggestions and happy to change the paper accordingly.

The introduction section is very long and contains excessive historical and general Roman context; is this necessary? It has been determined that it should be shortened to focus on the research gap, objectives, and innovations.

Answer: The Introduction part has been reduced from 7 pages to 4 pages. We focused on the research gap, objectives, and innovations.

The results section mixes explanations, dates, and interpretations without clear subheadings. It is thought that dividing it into sections as follows would be easier for the reader: 3D Reconstruction Material Characterisation (SEM-EDS, CLSM, AFM), Environmental Correlation (CIELAB, PCA), Conservation Assessment (HAp activity), 3D reconstruction lacks methodological reproducibility (data resolution, image overlap, software parameters). The inclusion of this information will improve the quality of the article. Improvements should be made in terms of writing and linguistics.

Answer: We took into account your suggestions and divided the text into sections, as you mentioned. Thank you!

The innovation should be clearly stated: ‘This study presents, for the first time, an archaeometric-digital reconstruction and HAp nanocoating evaluation for a Roman fortress on the banks of the Danube River.’

Answer: We inserted the suggested phrase in the text. Thank you for your suggestion.

What is SEM EDS, AFM Analysis? Abstract too long.

Answer: We reorganized and shorten the abstract. Also, we inserted the explanation of the microscopic techniques.

Keywords can be improved.

Answer: The existing Keywords have been rephrased and some new ones have been added.

The introduction is too long and very complicated. I am in lost in the paper.

Answer: We reduced the Introduction part from 7 pages to 4 pages.

Please summarise the abstract and introduction, it could be very briefly what topic is, related studies, gaps and your innovation. Why is there also another title with history in the section?

Answer: We took into consideration your suggestions. The sub-chapter about history has been removed.

Line 348, which samples?

Answer: Mortar samples. We corrected and rephrased in the line

L123, Empire is.

Answer: Corrected

In the Discussion section, connect findings with relevant literature

Answer: We added many other reports from the literature

Some references should be fixed or improved: [47, 58 , etc]

Answer: Corrected

Conclusion is also too long; present bullet-style implications and limitations for clarity. Overall, it requires revisions.

Answer: We reconsidered and rephrased the Conclusion chapter.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have duly responded to the reviewers' concerns the paper merits publication.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors took all comments into account and significantly improved the quality of the document by documenting the results and providing arguments for the proposed analyses.

Reviewer 4 Report

Comments and Suggestions for Authors

THe comments answered with revision, only some style things need to be improved. But I believe it is possible to crrect by technical team.