Review Reports

Round 1

Reviewer 1 Report

Dear authors,

Please, take care of the language. The abstract and the introduction up to line 61 is very difficult to read because of the language. From line 61, the text is a whole different thing. Furthermore, some elements from the first part are also in the second part, but way-way better written. For example, the abbreviation of EDX is wrongly stated in the abstract, the same in FTIR (transformed).

Apart from the language, the results and discussion section is very confusing. Text that can be related to introduction or discussion is fully provided, with a minor amount of results. Three different painting layers are under examination. What is the stratigraphy? What are the detected layers? What are these layers composed to? What does the analysis of the superficial layers show? Metallic soaps? How are these distributed? This is a logical sequence, that leads to the main object of this work, which is the study of degradation products. It is very confusing to state -from the beginning- that you have zinc carboxylates. One might attribute this to assumptions. The same applies to the identification of the materials/pigments present, such as Prussian blue, viridian, azurite, ultramarine-lapis, emerald green, Cr2O3-Fe3O4, ZnO/ZnS, malachite. These pigments can be easily molecularly identified (FTIR of Raman). The authors might be accused of assumptions if they are only based in elemental analysis. Finally, check the use of ZnO to drying oils.

 Some points to be taken care of.

Line 47: Sorry, maybe I haven’t heard this before, but what is hardwood (lime)?

Line 90: as it is mentioned/as we mention (this manuscript has 6 co-authors)

Line 90: red ocher is iron oxide, yellow ocher is iron oxide-hydroxide.

Lines 135-136: Please, rephrase.

Figure 2 caption: “with detached and not useful pieces used for sampling” please, rephrase

Lines 141-145: As long as the FTIR spectra were collected in transmittance mode, why are ATR and DRIFT accessories mentioned? Where the samples analyzed with the KBr technique?

Lines 158-167 & Table 1, regarding the chromatic parameters: Chromatic parameters differences are used to compare changes/color alterations. In this case, as long as the “after” of each examined area is the sample in its present state, how was the “before” calculated? In the case that these data refer to single measurements performed on the samples, L*, a* & b* are the correct expressions. In this case, the total chromatic difference ΔΕ cannot be calculated (it is a difference).

Table 1: Please, take care of the arrows and their description. I.e, in the first image, is this a green? In the second image, the right arrow points to the name of the painting with a description of “red robes”

Results and discussion section. The presentation is a little bit confusing. For example, in lines 194-210. This section better belongs in the introduction, OR after presenting some results it can be characterized as “discussion”.

Figure 3 and relative text. I am somehow confused regarding the images. Are they of the same blue sample, with different angles? I can observe a black painting layer over a white ground, am I missing something? Citation 45 that is used in line 219 doesn’t refer to OM identification of metallic soaps. In the following, lines 221-236 act again as a description of metal soaps’ appearing.

Figure 4 and related text. On what data is ImageJ manipulation based? The OM image should be also present. But in this case, how about the z-axis? How was depth measured (dimensions are missing in the image, a scale bar would be ok). “the case of the pigment is presented blue”, what about the other colors of this 3d-mapping? “It can be observed that the metallic layer of soap is lifted over the support, being detached from the main pictorial layer and is mixed with the intermediate layers” I assume tha the soap layer is under magenta/red color. How do the authors support its detachment from the painting layer?

Figure 5. Are the images collected with transmitted light? No transparency is visible.

Line 261. Is citation 49 correct? The authors present a SEM applications review for paintings, nothing regarding nucleation process in different areas is referred.

Line 261. Until now, in the results section, it is stated that there is a superficial layer. How can this layer be attributed to carboxylates, and especially zinc carboxylates at this point, if elemental and FTIR analyzes are not yet presented?

Figure 7. As long as the next table (please renumber it to “table 2”) exists, these EDS images do not add something extra to the manuscript, and the elements and the elemental analysis are too small to be comprehended.

Page 10, elemental analysis table. No description is presented in the manuscript. What are the pigments under consideration? Where do the authors attribute the presence of zinc and Ba? P is associated with bone black.

Figure 9. Please present the x-axis from 4000 to 400 cm−1, this is the most usual way for FTI spectra presentation. How were the spectra collected? The small bands at 2400-1900 cm-1 are usually present in diamond-ATR measurements. If this is the case, why were the spectra transformed to T? Is T in %? The maximum intensity is of ~1.0. All three spectra present extremely identical characteristics. Please, check for calcite (1440, 875, 712 cm−1). XRF?

Lines 333-341. The characteristic bands of hematite should be annotated in the spectrum. The referred “tarigrad pigment”, natural earth pigments such as ochres do contain aluminosilicates. Any silicate or aluminosilicate detection in the FTIR spectra?

Lines 342-344. Both ultramarine and lazurite can be identified through FTIR analysis. Its too bad that micro-FTIR could not be applied, to scan single pigment grains. Again, where do the authors attribute the presence of ZnO? And how can they be sure that this is ZnO and not ZnS?

Lines 345-351. Celadonite and glauconite can be detected also through FTIR. Nevertheless, the elemental analysis shows this direction. The rest of the proposed pigments cannot be stated with this kind of certainty.

Lines 360-371. This paragraph serves mostly as survey of the manuscript of Meilunas. As long these bands are justified in lines 287-309, what is the scope of this paragraph?

Lines 403-407. The majority of these pigments are firstly referred here. I’m afraid that this is out of context. Maybe something like “their identification is not part of the present work” can be added. Carbon black can be identified via Raman, how about the presence of P?

Author Response

Dear reviewer,

 

Thank you for your comments and suggestions sent in order to improve the quality of this paper.

I will try to answer below at your requests.

Please, take care of the language. The abstract and the introduction up to line 61 is very difficult to read because of the language.

Answer: We rephrased the first paragraph accordingly.

From line 61, the text is a whole different thing. Furthermore, some elements from the first part are also in the second part, but way-way better written. For example, the abbreviation of EDX is wrongly stated in the abstract, the same in FTIR (transformed).

Answer: Corrected

Apart from the language, the results and discussion section is very confusing. Text that can be related to introduction or discussion is fully provided, with a minor amount of results. Three different painting layers are under examination. What is the stratigraphy? What are the detected layers? What are these layers composed to? What does the analysis of the superficial layers show? Metallic soaps? How are these distributed? This is a logical sequence, that leads to the main object of this work, which is the study of degradation products. It is very confusing to state -from the beginning- that you have zinc carboxylates. One might attribute this to assumptions. The same applies to the identification of the materials/pigments present, such as Prussian blue, viridian, azurite, ultramarine-lapis, emerald green, Cr2O3-Fe3O4, ZnO/ZnS, malachite. These pigments can be easily molecularly identified (FTIR of Raman). The authors might be accused of assumptions if they are only based in elemental analysis. Finally, check the use of ZnO to drying oils.

 Answer: The stratigraphy has been done and all the measurements have been repeated. We followed your questions and answered accordingly.

Some points to be taken care of.

Line 47: Sorry, maybe I haven’t heard this before, but what is hardwood (lime)?

Answer: Corrected in lime tree

Line 90: as it is mentioned/as we mention (this manuscript has 6 co-authors)

Answer: Corrected

Line 90: red ocher is iron oxide, yellow ocher is iron oxide-hydroxide.

Answer: Rephrased

Lines 135-136: Please, rephrase.

Answer: Rephrased.

Figure 2 caption: “with detached and not useful pieces used for sampling” please, rephrase

Answer: Rephrased

Lines 141-145: As long as the FTIR spectra were collected in transmittance mode, why are ATR and DRIFT accessories mentioned? Where the samples analyzed with the KBr technique?

Answer: We reconsider all our data and we kept for this paper only ATR data

Lines 158-167 & Table 1, regarding the chromatic parameters: Chromatic parameters differences are used to compare changes/color alterations. In this case, as long as the “after” of each examined area is the sample in its present state, how was the “before” calculated? In the case that these data refer to single measurements performed on the samples, L*, a* & b* are the correct expressions. In this case, the total chromatic difference ΔΕ cannot be calculated (it is a difference).

Answer: We corrected and let the single measurements L*, a* and b*.

Table 1: Please, take care of the arrows and their description. I.e, in the first image, is this a green? In the second image, the right arrow points to the name of the painting with a description of “red robes”

Answer: We reconsidered the names

Results and discussion section. The presentation is a little bit confusing. For example, in lines 194-210. This section better belongs in the introduction, OR after presenting some results it can be characterized as “discussion”.

Answer: We moved this text at Discussion

Figure 3 and relative text. I am somehow confused regarding the images. Are they of the same blue sample, with different angles? I can observe a black painting layer over a white ground, am I missing something? Citation 45 that is used in line 219 doesn’t refer to OM identification of metallic soaps. In the following, lines 221-236 act again as a description of metal soaps’ appearing.

Answer: They are the same blue surface at different positions.We added a new explanatory paragraph in the text.

Figure 4 and related text. On what data is ImageJ manipulation based? The OM image should be also present. But in this case, how about the z-axis? How was depth measured (dimensions are missing in the image, a scale bar would be ok). “the case of the pigment is presented blue”, what about the other colors of this 3d-mapping? “It can be observed that the metallic layer of soap is lifted over the support, being detached from the main pictorial layer and is mixed with the intermediate layers” I assume tha the soap layer is under magenta/red color. How do the authors support its detachment from the painting layer?

Answer: We excluded ImageJ because is not very concludent.

Figure 5. Are the images collected with transmitted light? No transparency is visible.

Answer: We corrected these data.Because the optical microscopy couldn’t be repeated now, we replaced this technique by other techniques.

Line 261. Is citation 49 correct? The authors present a SEM applications review for paintings, nothing regarding nucleation process in different areas is referred.

Answer: We reorganized and replaced the entire list of references.

Line 261. Until now, in the results section, it is stated that there is a superficial layer. How can this layer be attributed to carboxylates, and especially zinc carboxylates at this point, if elemental and FTIR analyzes are not yet presented?

Answer: We added substantially data about FTIR.

Figure 7. As long as the next table (please renumber it to “table 2”) exists, these EDS images do not add something extra to the manuscript, and the elements and the elemental analysis are too small to be comprehended.

Answer: We deleted EDS images from the text.

Page 10, elemental analysis table. No description is presented in the manuscript. What are the pigments under consideration? Where do the authors attribute the presence of zinc and Ba? P is associated with bone black.

Answer: We included the requested data.

Figure 9. Please present the x-axis from 4000 to 400 cm−1, this is the most usual way for FTI spectra presentation. How were the spectra collected? The small bands at 2400-1900 cm-1 are usually present in diamond-ATR measurements. If this is the case, why were the spectra transformed to T? Is T in %? The maximum intensity is of ~1.0. All three spectra present extremely identical characteristics. Please, check for calcite (1440, 875, 712 cm−1). XRF?

Answer:Yes, calcite has been identified. Either on substrate or in the pigment mixture. Maybe this aspect will be clarified in the next papers.

We modified all the data accrdingly with the last measurements.

Lines 333-341. The characteristic bands of hematite should be annotated in the spectrum. The referred “tarigrad pigment”, natural earth pigments such as ochres do contain aluminosilicates. Any silicate or aluminosilicate detection in the FTIR spectra?

Answer: Yes, lazurite. It was mentioned in the text

Lines 342-344. Both ultramarine and lazurite can be identified through FTIR analysis. Its too bad that micro-FTIR could not be applied, to scan single pigment grains. Again, where do the authors attribute the presence of ZnO? And how can they be sure that this is ZnO and not ZnS?

Answer: From FTIR spectra of all potentially involved, could be observed that the white deposition is ZnO and ZnS.

Lines 345-351. Celadonite and glauconite can be detected also through FTIR. Nevertheless, the elemental analysis shows this direction. The rest of the proposed pigments cannot be stated with this kind of certainty.

Answer: Because the pictural layer is so complex, due to several restoration procedures occured in time, is a little too uncertain to identify celadonite and glauconite only by FTIR. The elemental analysis could complete this statement. The other pigments are not so easy to identify an is not in scope of this paper. We intend to address such complex aspects in our future papers.

Lines 360-371. This paragraph serves mostly as survey of the manuscript of Meilunas. As long these bands are justified in lines 287-309, what is the scope of this paragraph?

Answer: This paragraph has been deleted

Lines 403-407. The majority of these pigments are firstly referred here. I’m afraid that this is out of context. Maybe something like “their identification is not part of the present work” can be added. Carbon black can be identified via Raman, how about the presence of P?

Answer: Added the suggested sentence.

 

Kind regards

Prof. Rodica M.Ion

Author Response File: Author Response.docx

Reviewer 2 Report

Abstract:

Line  21: what authors mean by ‘16th Romanian heritage’?

Line 22: authors mentioned that church dates to 1730, so it is dated back to the 18^th century?

Introduction:

in this section, some literature data and previous analytical studies on similar constructions should be added. 

The church painting Samples:

the approx. size of the studied fragments should be given.

 Results:

Line 364: Why authors refer to malachite since no copper was measured in the EDS analysis?

Line 403: authors sated that pigments of ‘vermilion, azurite, green earth, lime white, smoke black, and red/yellow ochre’ were identified. However for the red pigment for example, EDS analysis did not reveal the detection of mercury ‘Hg’???

The results did not present the possible hypothesis that causes the formation of the metallic soaps and no recommendations for further protection of the paintings from these negative factors.

Author Response

Dear Reviewer,

 

Thanks a lot for your valuable suggestions to improve our paper.

Please find below our answers at your requests.

 

Abstract:

Line  21: what authors mean by ‘16th Romanian heritage’?

Answer: Rephrased snd corrected

 

Line 22: authors mentioned that church dates to 1730, so it is dated back to the 18^th century?

Answer: The 18th century lasted from January 1, 1701 to December 31, 1800. We think that this date is correct.

 

 

Introduction:

in this section, some literature data and previous analytical studies on similar constructions should be added. 

Answer: Done

 

The church painting Samples:

the approx. size of the studied fragments should be given.

Answer: 0.5 – 1 mm. We inserted into the text

 

 Results:

Line 364: Why authors refer to malachite since no copper was measured in the EDS analysis?

Answer: Without many other investigation techniques, which allow the identification of Cu, the pigment Malachite has been excluded from the list.

Line 403: authors stated that pigments of ‘vermilion, azurite, green earth, lime white, smoke black, and red/yellow ochre’ were identified. However for the red pigment for example, EDS analysis did not reveal the detection of mercury ‘Hg’???

Answer: The red color is due to red ochre. No Hg has been identified in our analysis. Vermilion has been excluded.

 

The results did not present the possible hypothesis that causes the formation of the metallic soaps and no recommendations for further protection of the paintings from these negative factors.

Answer:

We added new paragraphs with diagnosis, mechanism, and recommendations, both in the introduction and at the final part of the paper.

Kind regards

Prof. Rodica M.Ion

 

 

 

 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Dear authors,

Thank you for addressing all of my comments. The manuscript -and of course your study- is very interesting to read. Please, check the resolution of Fig. 1. This is a very interesting aspect of the church under investigation.