Disclosing Colors and Pigments on Archaeological Objects from the Aga Khan Necropolis (West Aswan Egypt) through On-Site Analytical Methods: Preliminary Results

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper is an interesting application of two spectroscopic techniques in situ, in an Egyptian archaeological site on materials used for mummification purpose. It would benefit the readers to have a more structured presentation of results, to have all tables in 1 or 2 ) like separately for first 3 cartonnages and for the other 1, as the analytical techniques are different. And the tables reporting ATR-FTIR results should include separately also the absorption peaks and the attributed compounds.

it is not clear what are the compounds identified for cartonnage AGH026-B41, the reflectance spectra and their PCA analysis only report colors for the points analyzed. The authors should explain better what the identification results are, as it seems that is not possible to correlate or compare these data with the data obtained from the other 3 cartonnages...it would make sense that this part is taken out and only the first 3 cartonnage data remains. The abstract claims that the cartonnages palette has been investigated, but the data from 4th one is not comparable and does not add much to the results of the 3 cartonnages analyzed with ATR-FTIR.

A suggestion would be to group the 4th cartonnage with the pottery and explain better why this investigation with Vis-RS was important and to which extent adds knowledge on the materials present in these objects.

Also please specify how was done the investigation with a USB microscope and what kind of microscope (a video one, or something different)? in the experimental part - check figure 4 for this.

At page 11, line 321 multispectral analysis from a campaign in 2021 is cited but no reference is given, if anything is available as report or publication.

Please check the line 216 (page 7) for a cm-1 error in writing the -1 (it has to be put up).

It woudl be nice to have a picture of the entrance to the tomb or an overal view of the necropolis.

After revision the paper can be recommended for publication.

Author Response

Answers to reviewer 1

The authors would like to thank the reviewer for the helpfull suggestions. Hereafter the responses to the various issues that have been raised are reported. The text has been modified accordingly.

The paper is an interesting application of two spectroscopic techniques in situ, in an Egyptian archaeological site on materials used for mummification purpose. It would benefit the readers to have a more structured presentation of results, to have all tables in 1 or 2 ) like separately for first 3 cartonnages and for the other 1, as the analytical techniques are different.

Precisely because the techniques are different, the last cartonnage was kept separate from the previous ones

 And the tables reporting ATR-FTIR results should include separately also the absorption peaks and the attributed compounds.

We may not have clearly understood what the reviewer means but the tables already contain the absorption peaks and the species to which the signals are ascribed. In any case the tables have been slightly modified also in accordance with the suggestions of the other reviewers.

it is not clear what are the compounds identified for cartonnage AGH026-B41, the reflectance spectra and their PCA analysis only report colors for the points analyzed.

The observation made by the reviewer is absolutely correct. First of all it is important to underline that unfortunately it was not possible to transport the fourth cartonnage to the magazine (where the other cartonnages were stored) due to permit issues (it has not been given permission to transport the cartonnage by the responsible authorities). As a consequence in this case it was possible only to acquire vis-RS measurements on some selected points.

The authors should explain better what the identification results are, as it seems that is not possible to correlate or compare these data with the data obtained from the other 3 cartonnages...

it would make sense that this part is taken out and only the first 3 cartonnage data remains.

In fact the technique employed is different and, as stated before, this was due to the impossibility of carrying the FTIR spectrophotometer directly on the excavation and,  on the other hand, to transport the cartonnage AGH026-B41 to the magazine.

The following sentence has been added in the text: Unfortunately, it was not possible to transport the fourth cartonnage to the magazine (where the other cartonnages were stored) due to permit issues. Despite this we feel it is important to emphasize that in this case the only technique that was transportable on the excavation, i.e. vis-RS, was used.”

In our opinion it was important to show how  under difficult and challenging working conditions, it is anyway possible to gather information on the chemical nature of the pigments used even though this information is certainly imcomplete. We have underlined this aspect in the text.

 The abstract claims that the cartonnages palette has been investigated, but the data from 4th one is not comparable and does not add much to the results of the 3 cartonnages analyzed with ATR-FTIR.

The abstract has been corrected from this point of view.

A suggestion would be to group the 4th cartonnage with the pottery and explain better why this investigation with Vis-RS was important and to which extent adds knowledge on the materials present in these objects.

At this purpose see the answer to the previous point.

Also please specify how was done the investigation with a USB microscope and what kind of microscope (a video one, or something different)? in the experimental part - check figure 4 for this.

This information has been added to the text.

At page 11, line 321 multispectral analysis from a campaign in 2021 is cited but no reference is given, if anything is available as report or publication.

The reviewer is right because  and in fact the text was unclear. The 2021 measurement campaign is that one during which the measurements presented in this article were performed (as it is explained in the introduction). Subsequently, additional measurements were performed on other cartonnages, by multi-spectral analysis (data not presented ni this paper) in the spring  2023.

 

Please check the line 216 (page 7) for a cm-1 error in writing the -1 (it has to be put up).

It woudl be nice to have a picture of the entrance to the tomb or an overal view of the necropolis.

This picture has been added in figure 1.

After revision the paper can be recommended for publication.

Reviewer 2 Report

Comments and Suggestions for Authors

Overall, the text would benefit from being more concise and the results of the FTIR analysis better presented (many repetitions). A table showing the main bands and their assignment would be better than a descriptive and repetitive text.
We are often reminded of the analyses that could not be carried out because sampling was impossible. It would be better to put this in the conclusion as a perspective, without including it in the results section.

Some particular remarks :

l.34 – replace « characterization chemical-physical » by « physico-chemical characterization »

l.49 « An extensive use of color has been made is cartonnages » sentence to check – « that has been made » ?

l.58 – correct « have put into » - « has highlighted » instead ?

l. 90 – replace « in other to » by « in order to »

l.195 to 201 – repetition with previous statement. « Nevertheless a laborious and careful preparation for the Italy-Egypt was necessary. » what do you mean by « for the Italy-Egypt » ?

l.332 – « that » two times, to correct

Comments on the Quality of English Language

It would be a good idea to review the English language, including punctuation
sentences often appear too long

Author Response

Answers  to reviewer 2

The authors would like to thank the reviewer for the helpfull suggestions. Hereafter the responses to the various issues that have been raised are reported. The text has been modified accordingly.

Overall, the text would benefit from being more concise and the results of the FTIR analysis better presented (many repetitions). A table showing the main bands and their assignment would be better than a descriptive and repetitive text.

The part of the results related to infrared spectroscopy has been revised and some repetitions removed trying to make the text more concise. particularly many band assignments that were repetitive were removed from the text and left only in the tables.

We are often reminded of the analyses that could not be carried out because sampling was impossible. It would be better to put this in the conclusion as a perspective, without including it in the results section.

The text has been modified accordingly.

Some particular remarks :

l.34 – replace « characterization chemical-physical » by « physico-chemical characterization »

it has been corrected

l.49 « An extensive use of color has been made is cartonnages » sentence to check – « that has been made » ?

the sentence has been modified

l.58 – correct « have put into » - « has highlighted » instead ?

it has been corrected

1. 90 – replace « in other to » by « in order to »

it has been corrected

l.195 to 201 – repetition with previous statement. « Nevertheless a laborious and careful preparation for the Italy-Egypt was necessary. » what do you mean by « for the Italy-Egypt » ?

the sentence has been modified; Italy-Egypt has been delated but this referred to the fact that the project is a collaboration between Italy and Egypt.

l.332 – « that » two times, to correct

the sentence has been corrected

 

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors. Thank you for your very interesting and unique work. The problem of instrument transport to Egypt is understandable and that nothing more could be done regarding this; to some, this work will seem as incomplete, but very useful results came up by just the FTIR analysis. I have issues with the interpretation of the FTIR spectra in some cases, I have issues with the necessity of presenting the spectrophotometric investigation, and, finally, check your whole manuscript for some language issues, I have pointed out some in the following. I strongly believe that the manuscript should be considered for publication, after revision.

 

I have some major issues regarding the attribution of some of the FTIR bands. To be precise, (everything is explained in the following), the direct attribution of “kaolinite” is a big no, consider replacing it with the general group ok kaolin. There is calcium oxalate and gypsum present.

 

Regarding the spectrophotometric results. I believe that this analysis, and the PCA analysis does nothing to enrich the manuscript. For example, the red painting layer is identified as of red color by Vis, and clustered as red by PCA. I don’t see any point in this, but please, let’s have the editor decide.

 

Issues

·         Figure 3. I don’t like the 1600 cm-1 band’s attribution to just water. This particular band is so intense only in the case of aqueous samples. Check if you have something (wide and less intense band or just a shoulder) at ~1320 cm-1. If this is the case, there are carboxylates (most probably calcium carboxylate) present. Its presence is justified by the degradation of something organic, like binder. Additionally, check reference spectra like gum Arabic. Check reference spectra of gypsum, maybe it is present but- of course- with very small participation.  

 

·         Lines 225-226. “like kaolinite (912, 596 and 530 cm-1)[28]. The presence of the latter would also justify the presence of water (3281, 1621 cm-1)[29] in the sample”. This is a strong NO. Check reference spectra of the kaolin group in the book of Chukanov you already use as reference. The kaolin type minerals, kaolinite included, present very very well localized (sharp and intense) hydroxyl bands at 3700-3200 cm-1. You have some indications of such bands in spectra B14, 2-B13 &3-B13, 2-B31 and 3-B31. Even in these cases, the participation of the amuninosilicate is very low to be able to distinguish between the minerals of the kaolin group. Finally, the wide at ~3200 ok, this is about hydroxyls, not water, while the ~1600 one can be attributed to the wide of carboxylates (you clearly have a band at 1320 in spectra 2-B13, and a shoulder in the same place in 3-B13, 3-B31), or to an organic binder. In 1-B31, the ~1600 is not organic. This is connected with a small participation of carboxylates. You have nothing at 3000-2800 of the CH groups. And to close this, check the water attributed bands in 3-B13, 2-B14, 2-B31 and 3-B31. These are connected with hydrous calcium sulfates, probably gypsum (their OH bands at 1680 & 1620 will be probably shown as “shoulders” as they are overlapped by the 1600 of calcium oxalate).

 

·         Whole document. Illite. Its very dangerous to identify it just by one band.

 

 

Minor issues

·         2.2.1 Is this a diamond ATR accessory? And, please revert to 4000-400 cm-1. Why are the spectra presented in T%? How were the grains collected? Were they kept after the analysis?

·         2.2.2. Measurement conditions? In terms of resolution and number of scans. What are the dimensions of the scanning window? Where the authors able to perform the measurements only to the desired painting area by masking, or neighbor areas also interfere?

·         L409. There is no software mentioned in the materials and methods section for performing PCA.

Comments on the Quality of English Language

Please, check the whole manuscript, I have pointed out some issues.

·         L22. the cartonnages’ palette was disclosed

·         L34. The chemical-physical characterization

·         L41. Precisely, in the Egyptian era, there is evidence…

·         L49. Extensive use of color was made in cartonnages

·         L57. “The excavations conducted since 2018 have put into that the necropolis covers a period ranging from the 6th century BC to the 2nd AD (about 800 years).” Please, rephrase.

·         L101. a group of other cartonnages

·         L155-156. (see paragraph 2.2) this can be excluded, as we are in paragraph 2.2.

Author Response

Answers  to reviewer 3

The authors would like to thank the reviewer for the helpfull suggestions. Hereafter the responses to the various issues that have been raised are reported. The text has been modified accordingly.

Comments and Suggestions for Authors

Dear authors. Thank you for your very interesting and unique work. The problem of instrument transport to Egypt is understandable and that nothing more could be done regarding this; to some, this work will seem as incomplete, but very useful results came up by just the FTIR analysis. I have issues with the interpretation of the FTIR spectra in some cases, I have issues with the necessity of presenting the spectrophotometric investigation, and, finally, check your whole manuscript for some language issues, I have pointed out some in the following. I strongly believe that the manuscript should be considered for publication, after revision.

 

I have some major issues regarding the attribution of some of the FTIR bands. To be precise, (everything is explained in the following), the direct attribution of “kaolinite” is a big no, consider replacing it with the general group of kaolin. There is calcium oxalate and gypsum present.

We thank the reviewer for suggestion; we have modified the text and the attribution of the signals accordingly.

Regarding the spectrophotometric results. I believe that this analysis, and the PCA analysis does nothing to enrich the manuscript. For example, the red painting layer is identified as of red color by Vis, and clustered as red by PCA. I don’t see any point in this, but please, let’s have the editor decide.

We would like to emphasize that, in addition to information about the chemical nature of the pigment, which can be attended to in this case by reflectance spectra, PCA allows us to point out differences or similarities between spectra that cannot be picked up simply by a visual comparison of reflectance spectra. While this type of approach is not exhaustive, we nevertheless believe that it can provide useful insights. For this reason we think it is useful to keep this part in the text.

 

Issues

• Figure 3. I don’t like the 1600 cm-1 band’s attribution to just water. This particular band is so intense only in the case of aqueous samples. Check if you have something (wide and less intense band or just a shoulder) at ~1320 cm-1. If this is the case, there are carboxylates (most probably calcium carboxylate) present. Its presence is justified by the degradation of something organic, like binder. Additionally, check reference spectra like gum Arabic. Check reference spectra of gypsum, maybe it is present but- of course- with very small participation.  

We thank  the reviewer for the precious observation. In fact, we have now added this hypothesis of attribution in the text. We have checked the reference spectrum of Arabic gum but, because of the other species present in the sample, it is not possible to identify this specie and as a consequence the sentence was delated.

• Lines 225-226. “like kaolinite (912, 596 and 530 cm-1)[28]. The presence of the latter would also justify the presence of water (3281, 1621 cm-1)[29] in the sample”. This is a strong NO. Check reference spectra of the kaolin group in the book of Chukanov you already use as reference. The kaolin type minerals, kaolinite included, present very very well localized (sharp and intense) hydroxyl bands at 3700-3200 cm-1. You have some indications of such bands in spectra B14, 2-B13 &3-B13, 2-B31 and 3-B31.

Thank to the reviewer for suggestion. In fact we have checked and the signals in the range 3700-3200 due to hydroxyl group are present. We have modified accordingly to this the assignments in the table and in the text. The band at 1600 cm-1, when any other signal at 1320 was present, is probably due to some water.

 Even in these cases, the participation of the amuninosilicate (??here is not clear what the reviewer means) is very low to be able to distinguish between the minerals of the kaolin group.

 Finally, the wide at ~3200 ok, this is about hydroxyls, not water, while the ~1600 one can be attributed to the wide of carboxylates (you clearly have a band at 1320 in spectra 2-B13, and a shoulder in the same place in 3-B13, 3-B31), or to an organic binder.

The presence of this signal due to some carboxylate has been highlighted also for these samples.

 In 1-B31, the ~1600 is not organic. This is connected with a small participation of carboxylates. You have nothing at 3000-2800 of the CH groups. And to close this, check the water attributed bands in 3-B13, 2-B14, 2-B31 and 3-B31. These are connected with hydrous calcium sulfates, probably gypsum (their OH bands at 1680 & 1620 will be probably shown as “shoulders” as they are overlapped by the 1600 of calcium oxalate).

In fact in sample 3-B13 gypsum has been highlighted. For the other samples it is not possible clearly identify it. In any case a precise assignment  only on the base of FTIR signals is not possible.

• Whole document. Illite. Its very dangerous to identify it just by one band.

We have delated the assignment.

 

Minor issues

• 2.2.1 Is this a diamond ATR accessory? And, please revert to 4000-400 cm-1. Why are the spectra presented in T%? How were the grains collected? Were they kept after the analysis?

Yes, it was a diamond accessory; the spectra are in transmittance, as reported in all the figures; these details were added in the experimental part.

• 2.2.2. Measurement conditions? In terms of resolution and number of scans. What are the dimensions of the scanning window? Where the authors able to perform the measurements only to the desired painting area by masking, or neighbor areas also interfere?

64 scans were performed, as reported in the text; no masks were employed since the fragments were directly put on the accessory.

• L409. There is no software mentioned in the materials and methods section for performing PCA.

The software employed was Statistica. This detail has been added in the text.

 

Comments on the Quality of English Language

Please, check the whole manuscript, I have pointed out some issues.

• L22. the cartonnages’ palette was disclosed
• L34. The chemical-physical characterization
• L41. Precisely, in the Egyptian era, there is evidence…
• L49. Extensive use of color was made in cartonnages
• L57. “The excavations conducted since 2018 have put into that the necropolis covers a period ranging from the 6th century BC to the 2nd AD (about 800 years).” Please, rephrase.
• L101. a group of other cartonnages
• L155-156. (see paragraph 2.2) this can be excluded, as we are in paragraph 2.2.

All these corrections have been introduced.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I woudl recommend that all corrections are accepted and then another editing is done after as some words are still not properly written, but I suppose it is only a mater of more attention to be paid to the final text.

Comments on the Quality of English Language

See above

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript has been improved according to the first report. It could be made even more concise.

Comments on the Quality of English Language

The quality of english has been improved compared to the first version.

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors,

Thank you for taking into consideration my comments! This is a very interesting work.

Best regards.

Comments on the Quality of English Language

Nothing more to add.