Non-Destructive and Micro-Invasive Techniques for Characterizing the Ancient Roman Mosaic Fragments

Round 1

Reviewer 1 Report

I found this article very interesting and important. They convincingly present their methods and results. The article focus on the technical aspects but I would urge the authors to elaborate on the implications of their finds in the study of ancient mosaics. For example - what type of tesserae were use in the mosaic, are they all locally quarried or imported from elsewhere? DO the different shades come from one stone or from different geological form?  

Author Response

In Introduction section was inserted the paragraph:

“A mosaic is a pictorial work elaborated with a set of tesserae joined between them by lime [16] or other binders to form geometric or figurative decorative compositions. Tessera is an individual piece of cubic form, made of calcareous rocks, glass or ceramic material [17]. In Ancient Rome the used tesserae were made of calcareous rocks obtained from local sources of natural stone, with additions of crushed brick, tile and pottery in order to create some colored shades: black, red, white, blue and yellow [18].”

Author Response File: Author Response.docx

Reviewer 2 Report

Non-Destructive and Micro-Invasive Techniques for 2 Characterizing the Ancient Roman Mosaic Fragments

 

The paper by Ion et al reports on the chemical characterisation of Roman mosaic fragments by a wide range, and impressive, techniques, namely: chromatic analysis, neutron diffraction, neutron tomography, optical microscopy, X-ray diffraction,  scanning electron microscopy - Energy Dispersive X-ray spectroscopy and Raman spectroscopy. The paper summarises the key results from these techniques and reports the chemical composition of different mosaics. The paper is well written and very clear and easy to follow, however, before being able to recommend publication I recommend the following amendments:

The larger amendments are as follows:

• I feel a discussion section is missing that brings the results together. This would make it easier for the reader to obtain the key results. Also, in this section, the implication of the results is needed. What does this mean for cultural heritage? Does it tell us anything about the environment these mosaics were created (social, techniques, technologies, etc)? This is suggested in the conclusion but I think it needs to be expanded on
• There is a considerable amount of techniques used and this should be commended. However, this also requires more information on the results. For example, some techniques are surface, some are near-surface and others are bulk (I’m thinking of the neutron techniques here). Therefore, this should be explained in some detail. Perhaps this can be included in the discussion section.
• Some results report the errors in the measurements very nicely whilst for others it is missing. This information is key when reporting on a range of techniques and comparing. In particular, neutron diffraction phases 45:55 (p12). Also, it should be included that this is mass or chemical %. Table 2 also requires errors. The authors should go through the paper and amend it as appropriate.

Smaller

• Figures 2 and 3 could be improved by showing the differences between X-ray/EDS spectra.
• Figure 4 could be improved by labeling the tentative identification
• Table 4: I am worried about the tentative assignments. Why is it tentative?
• Line 238: Does pure carbon always imply soot is used as a colorant? A citation here would be useful. Could there have been a ‘sooty environment’?
• Line 254: The most mosaic fragments needs rephrasing, probably Most mosaic fragments
• Why does the calcite have different lattice parameters? Comment here would be useful for the reader.
• Neutron diffraction: Can more information on the clays be obtained from the amorphous background?

In summary, a nice paper but I believe if the above amendments are made then it would be suitable for publication.

 

Author Response

1. I feel a discussion section is missing that brings the results together. This would make it easier for the reader to obtain the key results. Also, in this section, the implication of the results is needed. What does this mean for cultural heritage? Does it tell us anything about the environment these mosaics were created (social, techniques, technologies, etc)? This is suggested in the conclusion but I think it needs to be expanded on.

 

We included in the manuscript a short history of Roman Mosaic from Constanta, mentioning all the data that we found about the materials and possible technology to prepare the mosaic. Unfortunately, there are not so many literature references about this mosaic, so was not so easy to justify all the requested aspects.

 

2. There is a considerable amount of techniques used and this should be commended. However, this also requires more information on the results. For example, some techniques are surface, some are near-surface and others are bulk (I’m thinking of the neutron techniques here). Therefore, this should be explained in some detail. Perhaps this can be included in the discussion section.

 

In the Results and discussion section, the following paragraphs were added:

“For this research, quite complex objects of cultural heritage as the fragments of ancient mosaics were studied. The samples contain the main components, such as calcite and quartz, the colorant phases, the phases of decorative elements, the phases of clay, etc. For a comprehensive analysis of the samples, various methods were used. For color characteristics - spectroscopy, for phase analysis attracted X-ray diffraction. It is known, the experimental data on the chemical and mineral composition obtained from the surface of the massive objects may differ dramatically from the distribution of chemical components in its volume. In this case, the use of non-destructive methods with high penetration into the bulk objects looks justified. Neutron diffraction method provides information about the phase composition of the studied object and neutron radiography and tomography allow obtaining the pattern of the spatial distribution of internal components. The fundamental difference in the nature of neutron interactions with matter compared to X-rays provides additional benefits including sensitivity to light elements, a notable difference in contrast between neighboring elements. All these features make neutron methods a highly growing tool in archaeology science applications.

However, it seems that the main value of this study was precisely in the coordinated diverse research of the mosaic fragments. Also, the capabilities of various methods were demonstrated and these will provide a basis for future work on the classification and notification of numerous mosaics remains from other cultural centers.”

 

3. Some results report the errors in the measurements very nicely whilst for others, it is missing. This information is key when reporting on a range of techniques and comparing. In particular, neutron diffraction phases 45:55 (p12). Also, it should be included that this is mass or chemical %.

 

It is a volume fraction. We need accurate data for density for a mass calculation.

 

4. Table 2 also requires errors. The authors should go through the paper and amend it as appropriate.

 

In Table 2 the S.D.% values were inserted

 

5. Figures 2 and 3 could be improved by showing the differences between X-ray/EDS spectra.

 

XRD spectra are difficult to be overlapped, but from EDS spectra, the figure from Supplementary Material was drawn.  

 

6. Figure 4 could be improved by labeling the tentative identification

 

Figure 4 was replaced.

 

7. Table 4: I am worried about the tentative assignments. Why is it tentative?

 

The “tentative assignments” is widely used in the terminology of Raman spectroscopy.

8. Line 238: Does pure carbon always imply soot is used as a colorant? A citation here would be useful. Could there have been a ‘sooty environment’?

 

The phrase was rewritten and a citation was inserted.

 

9. Line 254: The most mosaic fragments needs rephrasing, probably Most mosaic fragments

 

The sentence was rewritten.

 

10. Why does the calcite have different lattice parameters? Comment here would be useful for the reader.

 

It can be seen that the parameters “a” for calcite phases are the same within the experimental errors. The smaller difference of the c parameters is explained by the presence of a very small number of impurities in such natural materials as a mosaic rock. The averaged bulk character of the neutron diffraction data, the presence of impurity phases and their small content cannot serve as a basis for making any assumptions or explaining the origin of the mosaic fragments, or the processes occurring in them.

The following sentence was inserted in the manuscript:

“A small difference in the c parameters of the unit cell of the calcite phases can be explained by the presence of a small amount of impurities in the rock samples of the studied mosaic fragments.”

 

11. Neutron diffraction: Can more information on the clays be obtained from the amorphous background?

 

It is very difficult to obtain results about the amorphous phase from neutron diffraction data. Only the fraction of the amorphous phase can be roughly estimated in comparison to samples without amorphous phases.

Author Response File: Author Response.docx

Reviewer 3 Report

The authors have applied a huge variety of scientific measurements on pieces of an ancient Roman mosaic. Measurement details were given for all methods, so they can be reproduced, but it is my regret that very few conclusions were drawn from the measurements - they were mostly presented 'as-is'.

I belive that this publication may serve as a good database for scientists doing more research into mosaics, concerning their making and their future restoration, with identical materials from the same materials and/or origin, and also as an example what choice of methods may be applied.

As a standalone publication, the interest to a general audience may be somewhat limited, since no interesting conclusions were drawn, e.g. whether materials are natural, or specifically made, of what origin...

The text needs several minor grammatical corrections. I have inserted as comments what corrections I found in the attached file.

 

Comments for author File: Comments.pdf

Author Response

1. As a standalone publication, the interest to a general audience may be somewhat limited, since no interesting conclusions were drawn, e.g. whether materials are natural, or specifically made, of what origin...

 

The materials used at the Roman Mosaic are marble and natural stone, of different colors. We included in the manuscript a short history of Roman Mosaic from Constanta, mentioning all the data that we found about the materials and possible technology to prepare the mosaic. Unfortunately, there are not so many literature references about this mosaic, so was not so easy to justify all the requested aspects.

 

2. The text needs several minor grammatical corrections. I have inserted as comments what corrections I found in the attached file.

 

All suggested corrections were done.

Author Response File: Author Response.docx

Reviewer 4 Report

This paper described different techniques to characterize ancient Roman mosaic fragments. Techniques were clearly explained with a long list of references for each then results of experiments were shown. It was interesting to see all those techniques working in parallel to confirm the results found. The authors took the time to show the data for each technique with simple and easy to read table/graph. I appreciate the fact that they do not fall in the mistake of just showing data and data without the real meaning behind it. 

I would have just a few minor changes and suggestions for the authors:

• Abstract: nicely written but I would insist a little bit more about why the ready should keep reading the paper. Why spend all this time on this sample behind just finding the composition. they are so many applications such as allowing those data to be used as a reference to other sample found in order to authenticate them, or at least make sure they are coming from the same part of the world, etc. (such as what you listed in line 67)
• In the abstract, you are listing the techniques used to study but it seems like you add one more that is not listed in the abstract, "wavelength dispersion x-ray fluorescence".
• Line 51: A nice explanation of the word "mosaic" but what is the meaning of "Muza"?
• line 60: I didn't get the meaning of the sentence. Can you double check the english? (... "be taken into consideration"? Maybe use ... "was taken into consideration" instead)
• Please add a scale to figure 1
• Figure 2: You can easily reduce the size of those plots but please provide better quality plots.
• line 199: I think you meant "it should be noted..."
• table 3: I think ND means no data but still, define it in the legend.
• line 237: line 4, 5 and table 4 (comma is missing)
• table 5: make sure the full table (header and contains) ends up int he same page for readability. 
• line 246: what exactly are H*, C*...... maybe Hx?

Author Response

1. In the abstract, you are listing the techniques used to study but it seems like you add one more that is not listed in the abstract, "wavelength dispersion x-ray fluorescence".

 

In the abstract was inserted the “wavelength dispersion x-ray fluorescence” technique.

 

2. Line 51: A nice explanation of the word "mosaic" but what is the meaning of "Muza"?

 

“Muza” was replaced with “the muse”.

 

3. Line 60: I didn't get the meaning of the sentence. Can you double check the english? (... "be taken into consideration"? Maybe use ... "was taken into consideration" instead)

 

The phrase was rewritten.

 

4. Please add a scale to figure 1

 

The Figure 1 is a photo taken by one of the authors and it was not made perpendicularly on the mosaic to allow the insertion of the scale. Authors complete the Figure 1 caption with details regarding the surface presented in this photo (2 x 3.5 m²).

 

5. Figure 2: You can easily reduce the size of those plots but please provide better quality plots.

 

Figure 2 was replaced.

 

6. Line 199: I think you meant "it should be noted..."

 

The suggested correction was made.

 

7. Table 3: I think ND means no data but still, define it in the legend.

 

“nd” was defined in the legend of Table 3.

 

8. Line 237: line 4, 5 and table 4 (comma is missing)

 

The correction was made.

 

9. Table 5: make sure the full table (header and contains) ends up in the same page for readability.

 

The correction was made.

 

10. Line 246: what exactly are H*, C*...... maybe Hx?

 

The corrections were made.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

I wish to thank the authors for their improvements to the paper. This, I believe, has significantly improved the results. However, I think it would be good to have as part of the conclusion of what these results together mean for these mosaics and its historical context. Does it tell us anything about the people, construction methods etc. In addition, it would be good to add what voxel is being examined by each technique, i.e. surface? At what depth etc.  

 

Author Response

I wish to thank the authors for their improvements to the paper. This, I believe, has significantly improved the results.

1. However, I think it would be good to have as part of the conclusion of what these results together mean for these mosaics and its historical context.

The Conclusions section was improved by:

“It is for the first time when this historical edifice built in 4^th Century AD is studied through some representative fragments (i.e., tesserae).”

In Conclusions section is mentioned that “The comprehensive studies of cultural heritage items (i.e., tesserae) can demonstrate the possibilities of joint non-destructive control examination, both in terms of historical restoring the manufacturing technology of ancient Roman and Byzantine mosaics and the effects of structural and chemical degradation of valuable materials”.

2. Does it tell us anything about the people, construction methods etc.

The article does not aim to study people’s community or construction methods. The study does not represent a historical incursion in the 4^th Century AD, but, it refers to historical data provided by scientists. The main goal of the article is to characterize the original Roman mosaic fragments as a reference point for funding projects (i.e.  Bilateral  Project  04-4-1121-2015/2020,  between  Valahia  University of  Targoviste and  Joint  Institute for  Nuclear  Research,  Dubna,  Moscow  Region;  Protocol  4755-4-2018/2020 “Microstructural and compositional characterization of supports and coating layers on different substrates applied in biomaterials, photoelectrochemicals catalysis, and cultural heritage and by the project 51PCCDI/2018, financed by Romanian National Authority for Scientific Research (UEFISCDI) “New diagnosis and treatment technologies for the preservation and revitalization of archaeological components of the national cultural heritage”).

3. In addition, it would be good to add what voxel is being examined by each technique, i.e. surface? At what depth etc.

The concept of a voxel refers exclusively to the method of neutron tomography. A voxel is a three-dimensional pixel or minimum point in space from which we get information about the attenuation coefficient of a neutron beam. At this point (voxel), the data about the elements or density of the studied material is extracted. The voxel size in our work is 52x52x52 microns. In the neutron tomography method, we obtain a three-dimensional model of the studied object consisting entirely of voxels. Typically, an object model consists of tens of millions of voxels. We do not consider surface effects in neutron tomography, but volume effects. Therefore, the neutron tomography method is a unique method for studying internal or bulk structures. It should be noted that neutron scattering methods have very high penetrating abilities: neutrons can penetrate into a stone object up to tens of centimeters. For a more explanation of the principles and features of neutron related methods, we provide the appropriate overview references in the paper, for example – [Treimer, W. Neutron Tomography. In Bilheux, H.Z.; McGreevy, R.; Anderson, I.S. (Eds.) Neutron Imaging and Applications; Springer-Verlag: Boston, MA, United States of America, 2009; pp. 81-108.] and [Kardjilov, N.; Festa, G. (Eds.) Neutron Methods for Archaeology and Cultural Heritage; Springer International Publishing: Switzerland, 2016, pp. 350].

Author Response File: Author Response.pdf