Assessment of Various Iron Extraction Treatments on Waterlogged Archaeological Oak
, Lorena Sozzi 2, Elodie Guilminot 1, Gwenaël Lemoine 1, Benedetto Pizzo 2, Jean Yves Mevellec 3, Elisa Pecoraro 2 and Mathilde Monachon 4Round 1
Reviewer 1 Report
Authors provided the information on various iron extraction treatments in waterlogged archaeological oak. However, it’s somewhat hard to find the significance and/or novelty in this manuscript, when compared to the previous works in this area. Furthermore, which treatment would be recommendable is not clearly specified, in terms of efficacy, treatment time, color changes and degree of damages to the wood components. Last but not least, rewording of contents is necessary to enhance the readability of the manuscript.
1.Introduction
It is desirable to clarify the (specific) purpose(s) of the investigation in Introduction.
2. Materials and Methods
2-1. It is wondering why authors applied qualitative index (= method of pin test) to evaluate the degradation rate for your samples, instead of quantitative methods to evaluate the degradation rate in waterlogged archaeological woods, such as maximum water content, density etc.
2-2. It is necessary to be informed what reliability and/or advantage of ATR to conventional FT-IR is for the evaluation of chemical characteristics in waterlogged archaeological woods.
2-3. The authors have to mention why FR-IR values were rechecked after 6 months and what for (Line 173).
2-4. “In hardwoods xylems only fibers…”(Line 207). This kind of generalization is hard to be accepted. How about vessel?
3. Results
3-1. Table 4: delta in the caption and table would be better to replace as “Δ”, which was already used in
3-1. Is there any correlation between iron extraction and colorimetric values? Did you have any attempt to make XY coordinates between iron extraction and L*, a*, b* and E*? In addition, is there any relationship between colorimetric values and extraction of corrosive products in waterlogged archaeological woods (refers to L. 439-441 in Discussion).
3-2. Anatomical characteristics in 3.2.2.
3-2-1. Authors mentioned “most of fiber cell walls were decayed, the S2 layer of secondary wall was often … middle lamella”. However, it is hard to observe such characteristics in the micrographs. Authors have to provide the suitable microphotographs showing their description. Otherwise, such anatomical characteristics can be noted as arrow and arrowhead in the micrographs to support their claims. In addition, it would be desirable to mention, what would be the main agent(s) of degradation (bacteria, fungi or abiotic agents) in this sample.
3-2-2. Polyphenolics (such as tannin) in parenchyma and vessels in oakwood would react closely with iron compounds. Extraction of polyphenolics in those tissues would be varied by chemicals. However, this study did not provide such information. Much more clear images showing the differences of iron extraction in the difference cell types are to be highly appreciated. Furthermore, any influence of tyloses in the vessel on extraction of iron is to be discussed.
3-2-3. Full and detailed information should be provided in caption of every Figures (Figs. 4-9) to enhance the readability of the contents.
3-3. Chemical characteristics in 3.2.3.
3-3-1. “more spongy” would not be a suitable scientific term to describe the degree of degradation.
3-3-2. Authors have to explain and discuss why different values of cellulose to lignin in wood samples were observed after 6 months.
4. Discussion
Which type of iron (Fe++ or Fe+++) or which components is mainly extracted by diverse treatment?
Color in wood samples was changed after 6 months or retained its original colorimetric values.
L.520. Literature should be added.
Table 5 shows that smile tag is in the order of oxalic acid (5) > citric acid (4) > EDTA & DTPA (2), whereas angry tags in the order of DTPA (3) > citric acid (2) > EDTA (1). How can the orders of smile and angry tags be explained for the efficacy of various treatments? To increase the significance and/or novelty of the manuscript, the efficacy of treatment methods is to be clearly and specifically explained for readers, when compared to previous works (literatures).
5. Conclusion
Conclusion should be concise and propose the further studies. In addition, some part (the first paragraph) can be moved to Discussion.
6. Miscellaneous
L.15. organic objects: what does it mean? Organic chemicals or organic materials?
L.18. were selected (for what?)
L.24 organic matter: what does it mean?
L.41 impregnating: what does it mean; impregnated or to be impregnating?
L.49. impact (to what?)
L.104-195: after dry overnight at RT, how about the moisture content of wood samples?
L.121: “in low depths” should be referred as arithmetic values.
L. 491: sur-face → surface
All the “quotation marks” in References should be deleted and “Pp” should be changes into “pp”.
L.587. Delete “In”, and “vol”
L.580. “et” → “and”
L. 603. Delete “The Japan Wood Research Society”
L.604, L.606, L.612 and L.625: How many authors can be allowed in citing the literature in case of “et al”? Please refer to the editorial guide line of in this journal Forests.
L.614 pHD → Ph.D.
L.615 and L. 633. Capital letters should be corrected.
L. 616. Delete “(luglio)”
7. References
Recently many papers in waterlogged archaeological woods were emerged from China. The authors have to pay attention to those literatures and other papers as well.
Broda M, CAS Hill. 2021. Conservation of Waterlogged Wood …, Forests 12(9):1193.
Gelbrich J et al. 2012. Evaluation of bacterial wood degradation by FTIR measurements. J. Cultural Heritage. 13(3):S135-S138.
High KE and K E. H. Penkman. 2020. A review of analytical methods for assessing preservation in waterlogged archaeological wood and their application in practice. Heritage Sci. 8:83
Pelé C et al., 2015. Iron removal from waterlogged wood… , Studies in Conservation 60(3):155-171.
Traoré M., et al. 2016., Application of FTIR spectroscopy to the characterization of archeological wood, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 153: 63-70
Wang Y et al. 2023. A New Bio-oxidation Method for Removing Iron Deposits from Waterlogged Wood of Nanhai I shipwreck, Guangdong, China. Engineering Microbiology 2023. Available online.
Zhang H et al. 2022. Characterization of degradation and iron deposits of the wood of Nanhai I shipwreck, Heritage Science 10:202.
Generally, the language could be checked throughout the manuscript, also e.g. the use of brackets and symbols should be consistent (for example considering the style of the references presented).
Author Response
Comments and Suggestions for Authors
Authors provided the information on various iron extraction treatments in waterlogged archaeological oak. However, it’s somewhat hard to find the significance and/or novelty in this manuscript, when compared to the previous works in this area. Furthermore, which treatment would be recommendable is not clearly specified, in terms of efficacy, treatment time, color changes and degree of damages to the wood components. Last but not least, rewording of contents is necessary to enhance the readability of the manuscript.
First of all, we'd like to thank you sincerely for taking the time to review this article and for your comments, which have helped us to improve it. We've tried to take them all into account and hope you'll be satisfied.
1.Introduction
It is desirable to clarify the (specific) purpose(s) of the investigation in Introduction.
- Materials and Methods
2-1. It is wondering why authors applied qualitative index (= method of pin test) to evaluate the degradation rate for your samples, instead of quantitative methods to evaluate the degradation rate in waterlogged archaeological woods, such as maximum water content, density etc.
The aim was to identify samples that were similar in terms of degradation and, above all, that came from the same archaeological object, in order to limit the known heterogeneity of archaeological samples. The needle test was therefore a quick and easy way of selecting similar samples, and it is representative of tests usually carried out in conservation laboratories, where not always MWC is measured. Moreover, we were not able to carry out MWC measurements on all the samples due to lack of enough sacrificial material.
2-2. It is necessary to be informed what reliability and/or advantage of ATR to conventional FT-IR is for the evaluation of chemical characteristics in waterlogged archaeological woods.
The attenuated total reflectance (ATR) device in IR analysis shows several advantages in comparison with the more traditional IR technique making use of KBr pellets, considering that it virtually allows acquiring spectra without any wood pretreatment. Only preliminary milling of wood is needed to obtain robust and reliable values but solely in dry matter, mainly because of the quality of the contact between meal and crystal. In contrast, working with wet wood allows for a better contact and higher signals, thus eliminating the need for any milling. This information is taken from Pizzo et al. (2013) "A New Method to Quantitatively Evaluate the Chemical Composition of Waterlogged Wood by Means of Attenuated Total Reflectance Fourier Transform Infrared (ATR FT-IR) Measurements Carried Out on Wet Material", which has been also quoted in the paper. Similar observations were also added to the text.
2-3. The authors have to mention why FR-IR values were rechecked after 6 months and what for (Line 173).
This permitted to evaluate the impact of iron extraction treatments time on the main components of wood, i.e. lignin and carbohydrates.
2-4. “In hardwoods xylems only fibers…”(Line 207). This kind of generalization is hard to be accepted. How about vessel?
The cell wall of vessels is thin, while in fibers is quite thick. The S2 layer of fiber cell wall is thick and rich in cellulose. The attack by bacteria is concentrated on cellulose, that’s why the attack is more effective on the cell wall of fibers and it is more visible there compared to vessel.
- Results
3-1. Table 4: delta in the caption and table would be better to replace as “Δ”, which was already used in
done
3-1. Is there any correlation between iron extraction and colorimetric values? Did you have any attempt to make XY coordinates between iron extraction and L*, a*, b* and E*? In addition, is there any relationship between colorimetric values and extraction of corrosive products in waterlogged archaeological woods (refers to L. 439-441 in Discussion).
The main changes concern L* values, which suggest surface lightening on all samples. The a* and b* values do not change significantly, except for the samples treated with oxalic acid, where Δb* increases towards the yellow shades. At this stage, and with this corpus, it doesn't seem relevant to us to interpret further on colorimetric values. On the other hand, it is clear that, depending on the ferrous compounds present on the surface and the chemical interactions with the extraction products, a relationship between colorimetric values and ferrous compounds could be attempted in a subsequent project.
3-2. Anatomical characteristics in 3.2.2.
3-2-1. Authors mentioned “most of fiber cell walls were decayed, the S2 layer of secondary wall was often … middle lamella”. However, it is hard to observe such characteristics in the micrographs. Authors have to provide the suitable microphotographs showing their description. Otherwise, such anatomical characteristics can be noted as arrow and arrowhead in the micrographs to support their claims. In addition, it would be desirable to mention, what would be the main agent(s) of degradation (bacteria, fungi or abiotic agents) in this sample.
We've modified some images and added arrows to focus observations. Captions have also been added to aid reading.
3-2-2. Polyphenolics (such as tannin) in parenchyma and vessels in oakwood would react closely with iron compounds. Extraction of polyphenolics in those tissues would be varied by chemicals. However, this study did not provide such information.
You're right, and we must admit that we've always wondered about this subject in the laboratory. We are familiar with this article, which deals precisely with polyphenols in archaeological wood https:///www.tandfonline.com/doi/pdf/10.1080/00393630.2020.1864895. We've added a sentence in the discussion to list this subject, but we don't have an answer here because it hasn't been studied.
Much more clear images showing the differences of iron extraction in the difference cell types are to be highly appreciated.
done with arrows
Furthermore, any influence of tyloses in the vessel on extraction of iron is to be discussed.
Tyloses have parenchyma walls and, normally, ray walls are more colored. Figure 4#22 shows some very colorful tyloses. The wood used for this work is always the same, and the tyloses (as always in oak heartwood) are clearly present. It seems to us that the extraction of at least the iron is influenced by the chemical used and not by the tyloses.
3-2-3. Full and detailed information should be provided in caption of every Figures (Figs. 4-9) to enhance the readability of the contents.
done
3-3. Chemical characteristics in 3.2.3.
3-3-1. “more spongy” would not be a suitable scientific term to describe the degree of degradation.
It was more to comment on the surface condition of the sample. We have modified and clarified the statement.
3-3-2. Authors have to explain and discuss why different values of cellulose to lignin in wood samples were observed after 6 months.
We have made this clear in the Materials and methods section, following comment 2-3.
- Discussion
Which type of iron (Fe++ or Fe+++) or which components is mainly extracted by diverse treatment?
For each complexing agent, we have indicated the affinities with the type of iron compound (ferrous / ferric).
Color in wood samples was changed after 6 months or retained its original colorimetric values.
The surface color of the samples has changed, but it's hard to say that the wood has regained its original color, which is difficult to identify on archaeological samples. The curator is trying to obtain the color of natural oak, but without too much risk of bleaching. It's more a question of attenuating the orange/black color due to the ferrous compounds.
L.520. Literature should be added.
Done
Table 5 shows that smile tag is in the order of oxalic acid (5) > citric acid (4) > EDTA & DTPA (2), whereas angry tags in the order of DTPA (3) > citric acid (2) > EDTA (1). How can the orders of smile and angry tags be explained for the efficacy of various treatments? To increase the significance and/or novelty of the manuscript, the efficacy of treatment methods is to be clearly and specifically explained for readers, when compared to previous works (literatures).
The purpose of the table is to show the effectiveness of the complexing agents, which varies according to the desired result. We couldn't really prioritize these treatments because they depend too much on what is expected. For example: EDTA is very good for extracting iron compounds, but it can take a long time and this could potentially lead to degradation of organic matter, when the time is too long. Oxalic acid can have a high impact on organic matter, but is very effective on the surface, returning a color closer to that of unpolluted wood. The next step would be to compile a list of all the articles and experiments carried out on the different types of wood treated, and to classify them according to criteria linked to the choice of preservatives.
- Conclusion
Conclusion should be concise and propose the further studies. In addition, some part (the first paragraph) can be moved to Discussion.
done
- Miscellaneous
L.15. organic objects: what does it mean? Organic chemicals or organic materials?
done
L.18. were selected (for what?) done
L.24 organic matter: what does it mean? done
L.41 impregnating: what does it mean; impregnated or to be impregnating? done
L.49. impact (to what?) done
L.104-195: after dry overnight at RT, how about the moisture content of wood samples? Monachon et al. 2020 (Microchemical Journal) studied the impact of this protocol on wood (balsa and Neolithic oak). This study demonstrated the feasibility and effectiveness of IP1 in reproducing some of the characteristics of waterlogged degraded wood, and modeling will continue to be improved for wood species frequently encountered in waterlogged wood artifacts, such as oak and pine. This study did not focus on the post-proofing stage.
L.121: “in low depths” should be referred as arithmetic values. done
- 491: sur-face → surface done
All the “quotation marks” in References should be deleted and “Pp” should be changes into “pp”. done
L.587. Delete “In”, and “vol” done
L.580. “et” → “and” done
- 603. Delete “The Japan Wood Research Society” done
L.604, L.606, L.612 and L.625: How many authors can be allowed in citing the literature in case of “et al”? Please refer to the editorial guide line of in this journal Forests. done
L.614 pHD → Ph.D. done
L.615 and L. 633. Capital letters should be corrected. done
- 616. Delete “(luglio)” done
- References
Recently many papers in waterlogged archaeological woods were emerged from China. The authors have to pay attention to those literatures and other papers as well.
CPM : Done we complete the literature according to your propositions, many thanks for that.
Comments on the Quality of English Language
Done, we've had the whole article professionally proofread to improve the language.
Generally, the language could be checked throughout the manuscript, also e.g. the use of brackets and symbols should be consistent (for example considering the style of the references presented).
CPM: done
Author Response File: 
Author Response.docx
Reviewer 2 Report
The article covers the topic of the assessment of various iron extraction treatments on water-logged archaeological oak. In my opinion, article presents valuable content. The subject and the supporting analysis are informative and present added value to the body of knowledge on the subject area. The topic of the article is in scope of journal. The article is clearly written and edited. The assumptions used in the analysis are correct and appropriate at this stage of the analysis. However, I have some critical remarks. The article requires some minor editorial corrections. The citation of literature is different from that used in MDPI publications. Table 1 is placed too far from where it is mentioned in the text.. In the final version, tables 1 and 2 should not be placed directly below one another, table 3 should not be split between the pages. Subsection 2.4.3 is wrongly numbered 4.3.
Author Response
Comments and Suggestions for Authors
The article covers the topic of the assessment of various iron extraction treatments on water-logged archaeological oak. In my opinion, article presents valuable content. The subject and the supporting analysis are informative and present added value to the body of knowledge on the subject area. The topic of the article is in scope of journal. The article is clearly written and edited. The assumptions used in the analysis are correct and appropriate at this stage of the analysis. However, I have some critical remarks. The article requires some minor editorial corrections. The citation of literature is different from that used in MDPI publications. Table 1 is placed too far from where it is mentioned in the text.
First of all, we'd like to thank you sincerely for taking the time to review this article and for your comments, which have helped us to improve it. We've tried to take them all into account and hope you'll be satisfied.
In the final version, tables 1 and 2 should not be placed directly below one another, table 3 should not be split between the pages.
We've placed the paintings as close as possible to the corresponding text, thus separating them.
Subsection 2.4.3 is wrongly numbered 4.3. done
Author Response File: Author Response.docx
Reviewer 3 Report
The topic of the study is interesting and important for the researchers working within the fields of wood conservation, chemistry and archaeology. The design of the study is clear and well planned, and the study is very well motivated.
I will just suggest some minor checking and corrections for the manuscript for possible improvements:
Generally, the language could be checked throughout the manuscript, also e.g. the use of brackets and symbols should be consistent (for example considering the style of the references presented).
Further, I would like to suggest following minor changes:
Abstract:
The objective and the main result of the study should be presented more clearly in the abstract.
The objective is given in one sentence (lines 22-26) which is too long, so it could be presented with two shorter and more clear sentences instead.
The same could be checked for the sentence presented in the lines 32-34.
Introduction:
Line 41: could there be given any references to these previous studies mentioned here?
Line 60, 64: please explain the acronyms EDTA, DTPA
Line 78: can any reference be given for the pin test? (Has this test been used in any previous studies published?)
Line 83: measured -> was measured to be
Section 2.2.
Why XRD and FTIR methods are described in “Impregnation process” section; could they be presented within their own subtitle, e.g. “Structural analysis”?
Line 119-120 (and Line 420-421): the identification of goethite and lepidocrocite should be more justified. The figures 2 and 3 do not show these compounds at all?
Lines 120-121: how the figures 2 and 3 should show that these compounds are found more on the surface? I think that this fact is not shown in these figures presented here. So also this fact should be justified for the reader more clearly.
Figure 2: the legend and the axis titles/numbers are difficult to read: they should be printed with a larger font and more clearly. Please check also the figure label (line 123). A note should be stated that the Xray diffraction peaks identified as pyrite are extremely faint (In my opinion, if I checked it correctly, I would not even state that they are present in the figure at all, because the statistics of the diffractogram is so low: only the halo of the amorphous cell wall matrix and the wide peak of the cellulose main reflection are observed.)
Results
Line 255: high variations -> higher variations
Line 260: please check this sentence (remove “such as”?)
Section 3.2.1 and table 4: ‘delta’ could be expressed everywhere with delta-symbol (similarly as in line 266, 267)
Line 342: maintains -> maintained
Line 348: ‘than citric acid alone’ -> ‘than in the sample treated with citric acid alone’
Line 373: in this sentence some expression is missing (probably: ‘which was more spongy..”?)
Line 403-405: please write this sentence more clearly
Figure 10: the various line colors (green/red/black) are difficult to detect. Please indicate the different colors better (the lines could be thicker and the colors more bright)
Discussion
Overall, the discussion should be checked to be a little bit more focused and clear. Now there were a few sentences whose meaning was not very clear. (See further details below)
Line 441: unclear sentence
Lines 448-449: also this one is an unclear sentence (something is maybe missing here?)
Conclusions:
The conclusions gather well the main points of the study, and many important notes are made here. I would suggest that these points (related to the initiation of the further studies/projects) could be mentioned already earlier in the manuscript: e.g. in the end of the Introduction (when the objective and scope of the study are presented for the reader).
The language could be checked by using some language model program and/or professionals, because there were some mistakes and some unclear expressions and sentences in the manuscript.
Author Response
Comments and Suggestions for Authors
The topic of the study is interesting and important for the researchers working within the fields of wood conservation, chemistry and archaeology. The design of the study is clear and well planned, and the study is very well motivated.
First of all, we'd like to thank you sincerely for taking the time to review this article and for your comments, which have helped us to improve it. We've tried to take them all into account and hope you'll be satisfied.
I will just suggest some minor checking and corrections for the manuscript for possible improvements:
Generally, the language could be checked throughout the manuscript, also e.g. the use of brackets and symbols should be consistent (for example considering the style of the references presented).
Done, we've had the whole article professionally proofread to improve the language.
Further, I would like to suggest following minor changes:
Abstract:
The objective and the main result of the study should be presented more clearly in the abstract.
Done
The objective is given in one sentence (lines 22-26) which is too long, so it could be presented with two shorter and more clear sentences instead.
Done
The same could be checked for the sentence presented in the lines 32-34.
Done
Introduction:
Line 41: could there be given any references to these previous studies mentioned here?
Done
Line 60, 64: please explain the acronyms EDTA, DTPA
Done
Line 78: can any reference be given for the pin test? (Has this test been used in any previous studies published?)
Cited in papers but this is a commonly technique used in the conservator area.
Done; the needle test is a test commonly used in conservation laboratories. We have supplemented the article with two references: one that cites this principle and a second that explains the principle of the needle test but via a Pylodin.
Line 83: measured -> was measured to be
Done
Section 2.2.
Why XRD and FTIR methods are described in “Impregnation process” section; could they be presented within their own subtitle, e.g. “Structural analysis”?
We understand this reviewer’s comment. However, considering that the results are directly quoted in the impregnation section and do not concern extraction, we have chosen to leave it in this section.
Line 119-120 (and Line 420-421): the identification of goethite and lepidocrocite should be more justified. The figures 2 and 3 do not show these compounds at all?
Lines 120-121: how the figures 2 and 3 should show that these compounds are found more on the surface? I think that this fact is not shown in these figures presented here. So also this fact should be justified for the reader more clearly.
Figure 2: the legend and the axis titles/numbers are difficult to read: they should be printed with a larger font and more clearly. Please check also the figure label (line 123). A note should be stated that the Xray diffraction peaks identified as pyrite are extremely faint (In my opinion, if I checked it correctly, I would not even state that they are present in the figure at all, because the statistics of the diffractogram is so low: only the halo of the amorphous cell wall matrix and the wide peak of the cellulose main reflection are observed.)
We have selected the most obvious figures, as they are limited. We have, however, reduced the diffractograms, which are confusing and detract from the presentation. It is through the reproducibility of the spectra that we have been able to identify pyrite by XRD and iron compounds by Raman. But pyrite and ferrous compounds make Raman fluoresce a lot, which sometimes makes it difficult to read the spectra. What's more, the spectra come out of a software package that we don't have in the lab, which prevented us from redrawing the figure correctly to improve readability.
Results
Line 255: high variations -> higher variations
done
Line 260: please check this sentence (remove “such as”?)
done
Section 3.2.1 and table 4: ‘delta’ could be expressed everywhere with delta-symbol (similarly as in line 266, 267)
done
Line 342: maintains -> maintained
done
Line 348: ‘than citric acid alone’ -> ‘than in the sample treated with citric acid alone’
done
Line 373: in this sentence some expression is missing (probably: ‘which was more spongy..”?)
done
Line 403-405: please write this sentence more clearly
done
Figure 10: the various line colors (green/red/black) are difficult to detect. Please indicate the different colors better (the lines could be thicker and the colors more bright)
We have captioned the samples on the spectrum.
Discussion
Overall, the discussion should be checked to be a little bit more focused and clear. Now there were a few sentences whose meaning was not very clear. (See further details below)
done
Line 441: unclear sentence
done
Lines 448-449: also this one is an unclear sentence (something is maybe missing here?)
done
Conclusions:
The conclusions gather well the main points of the study, and many important notes are made here. I would suggest that these points (related to the initiation of the further studies/projects) could be mentioned already earlier in the manuscript: e.g. in the end of the Introduction (when the objective and scope of the study are presented for the reader).
This is absolutely true. However, we would like to keep this general part in the conclusion, to make sure that the context is well remembered. In fact, conclusions is sometimes the only part that gets read and remembered in an article.
Comments on the Quality of English Language
The language could be checked by using some language model program and/or professionals, because there were some mistakes and some unclear expressions and sentences in the manuscript.
Done, we've had the whole article professionally proofread to improve the language.
Author Response File: Author Response.docx
