Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper is devoted to analysis of sinopia and tesserae of Byzantine-age mosaic of Armenian Chapel in Jerusalem. Authors use an extensive array of complementary methods. Identification of paint pigments and analysis of mineral composition of tesserae is carried out. An interesting result is correlation of carbon black and gypsym content - which may be useful for reconstruction of paint recipe.

In my opinion, the manuscript requires only minor revision, see detailed comments below.

 

Line 110 - Fig 1. A scale should be added to part f (stratigraphy scheme).

Line 124 - abbreviation TL-OM is not explained.

L 153 - comments should be added to explain why 1 gr of sample is required

L 177 - consider moving Table 1 to supplementary section

L 190-194. Table 2 and Fig 3 provide the same information. Consider removing one of them.

L 206. "red colorants in the tesserae are materials with different atomic structure". "Atomic" should be repalced with "crystal" or "molecular".

L 227 - "with low aliquot of quartz". Better is "with low quartz content"

L 234. Table 3 caption should include units (mass percent ?) of provided values

L 240. "The painted sinopia is composed mainly of Ca..." - better: "Elemental composition of sample is dominated by Ca..." - because sinopia is composed of calcium compounds, not pure calcium.

Comments on the Quality of English Language

Some minor language editing should be carried out, see e.g. L112 "thickness", L 129 "thorough", L 227 "aliquot".

Author Response

REVIEWER 1

 

In my opinion, the manuscript requires only minor revision, see detailed comments below.

 

Line 110 - Fig 1. A scale should be added to part f (stratigraphy scheme).

Text has been added to the legend: “Fig 1F. Each square is 1cm for scale.”

Line 124 - abbreviation TL-OM is not explained.

The text in row 124 has been amended to: “…transmitted-light optical microscope (TL-OM)”.

L 153 - comments should be added to explain why 1 gr of sample is required

Text has been added “ for homogenization”

L 177 - consider moving Table 1 to supplementary section

We think showing the analytical techniques used on the different samples is important

L 190-194. Table 2 and Fig 3 provide the same information. Consider removing one of them.

Table 2 has been removed

L 206. "red colorants in the tesserae are materials with different atomic structure". "Atomic" should be repalced with "crystal" or "molecular".

The word Atomic was replaced with the word molecular

L 227 - "with low aliquot of quartz". Better is "with low quartz content"

The text was replaced to “with low quartz content”

L 234. Table 3 caption should include units (mass percent ?) of provided values

The word percentages was added

L 240. "The painted sinopia is composed mainly of Ca..." - better: "Elemental composition of sample is dominated by Ca..." - because sinopia is composed of calcium compounds, not pure calcium.

The text has been amended to : “Ca-based materials”

 

Comments on the Quality of English Language

Some minor language editing should be carried out, see e.g. L112 "thickness", L 129 "thorough", L 227 "aliquot".

All these words were amended.

 

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

See attached file

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Minor editing

Author Response

Revision manuscript “Heritage-3101179”

Title:“Mosaic technology in the Armenian Chapel Bird Mosaic, Jerusalem: characterizing the polychrome hidden

sinopia”

Authors: Yotam Asscher *, Giulia Ricci, Michela Reato, Abraham Leviant, Ilana Peters, Jacques Neguer, Mark Avrahami, Gilberto Artioli.

 

 

The authors propose a very interesting archaeometric study about the polychromatic synopia and black and red tesserae of the “Birds Mosaic” in the Armenian Chapel, Jerusalem. The study takes into account samples of synopia mortar (red-black, red-white, black-white) and black and red tesserae, chosen as representative of the mosaic, and used all the most relevant analytical techniques to get information about the chemical compounds used in the mosaic production. I think that the work is relevant, well written and discussed, and suitable for publication on Heritage, apart from minor revisions and some points to be made cleare. I make some general comments and propose some minor revisions.

 

General comments:

 

• Since the authors cross XRD, Raman, FTIR, polarized TL-OM, and SEM-EDS analysis, which can provide details practically on any material of the taken samples, I wonder why they apply also FORS and XRF, which are non-invasive, but relatively less informative techniques. Is it carried out in view of a possible, future, non-invasive characterization of other points on the sinopia? If it is so, I can understand the point, but maybe the authors could explain this in a short sentence.

The non-invasive characterization will be published in another publication that is being prepared. New text was added to the materials and methods section to explain this:

“Non-invasive characterization was performed prior to well-established techniques that require sampling (the significance of the non-invasive approach will be discussed in future work).”

• Instead, the authors apply Raman to the synopia mortars but not to the tesserae, why? Fluorescence problems? The authors should make this point clearer.

Raman analysis on the tesserae did not produce good results, and yes, fluorescence was an issue that made the analysis difficult.

• In the discussion, the authors conclude that “the analysed tesserae (black and red) are both composed by a calcite-based matrix with no trace of hematite nor carbon black pigments” (line 336). Although the evidence from XRD supports the absence of hematite, as well FTIR (no Fe-O bands) and SEM-EDS (no Fe peak in T_R) in both the red and black tesserae, it is not clear to me which experimental evidence suggests the absence of amorphous carbon in the black tesserae. This is related also to the previous point, concerning Raman investigations: if the authors were unable to get Raman peaks related to carbon black or amorphous carbon on the black tesserae, this would probably support partially the

As Raman did not produce meaningful results on the black tesserae, we did perform dissolution of the black stones and run FTIR on the insoluble fraction, the results show that the molecular structure of the insoluble fraction is similar to that of bitumen. We added new text in the Results section (row 276): “The black tesserae were dissolved, and the insoluble fraction was analysed using FTIR. The spectra are similar to that of bitumen, containing vibrational bands of C-H organic compounds at 2852 and 2923 cm-1, that could derive from degradation of biogenic products and be responsible to the black color of the stones”.

 

And new text in the discussion section (row 353): “and the presence of C-H organic compounds in FTIR vibrational bands”

• The authors associate the black tesserae to the Hatrurim Formation, enriched in organic material, due to the presence of sulfur and biogenic nodules. My question is: where the black colour comes from? Were the FTIR spectra of black tesserae observed also in the 4000-2000 cm^-1 region? Did the authors observe peaks around 3000 cm^-1, where CH stretching from organic compounds are expected? The presence of peaks like those could be related to the presence of carbonaceous compounds deriving from biogenic origin, and supporting the black coloration (as normal for degradation by-products from bio-organic materials).

Yes, as explained above, the FTIR spectra of the insoluble fraction is similar to that of Bitumen (see below), with peaks in 2852 and 2923 cm^-1, that might be responsible for the black color of the stone.

 

• Line 264-265. The sentence is not clear to me. The authors should explain better the concept, since Heritage has a broad audience, and the relationship between FTIR and lattice disorder in calcium carbonate is not so straightforward. E.g., I propose to re-formulate the sentence as follows: “FTIR analysis of the tesserae, supporting mortar and painted mortars (sinopia), shows that they are based on calcite with different degree of atomic disorder. Indeed, the different relative heights of the peaks at about 870 cm^-1 (v2, out-of-plane carbonate bending) and about 710 cm^-1(v4, in-plane carbonate bending) in the IR spectra of calcite polymorphs have been related to atomic disorder in the lattice structure of calcium carbonate and can provide information on the type of calcium carbonate (plaster, chalk, lime). Following Regev et al. [32], in Figure 7, panel B, we plot the relative heights of v2 vs. v4 peaks in a graph with the expected trend lines for plaster, chalk, and lime.”

 

We thank the reviewer and changed the text according to his suggestions: “FTIR analysis of the tesserae, supporting mortar and painted mortars (sinopia), shows that they are based on calcite with different degree of atomic disorder. Indeed, the dif-ferent relative heights of the peaks at about 870 cm-1 (v2, out-of-plane carbonate bend-ing) and about 710 cm-1(v4, in-plane carbonate bending) in the IR spectra of calcite polymorphs have been related to atomic disorder in the lattice structure of calcium carbonate and can provide information on the type of calcium carbonate (plaster, chalk, lime). Following Regev et al. [32], in Figure 7b, we plot the relative heights of v2 vs. v4 peaks in a graph with the expected trend lines for plaster, chalk, and lime. Results show the mortars are indeed highly disordered, indicating they are well-preserved. The tes-serae have higher disorder values compared to limestone and chalk geological car-bonates, suggesting that the rocks from which the tesserae were quarried underwent processes of diagenesis or heating. In addition, to understand the color in the black tesserae, they were dissolved, and the insoluble fraction was analysed using FTIR. The spectra are similar to that of bitumen, containing vibrational bands of C-H organic compounds at 2852 and 2923 cm-1, that could derive from degradation of biogenic products and be responsible to the black color of the stones”

 

 

Minor revisions:

 

The manuscript title reports “Bird Mosaic”, whereas in the main text it is often (but not always) reported as “Birds Mosaic”. The authors should choose an “official” name.

The title was amended.

 

Line 49: The sentence “The first layer of mortar… acts as a gradient in sequence…with the lower soil and gravel” is not straightforward. I propose to explain the concept better: “A first layer of mortar with… (rudus) is placed above the statumen, and finally a fine upper layer of mortar (sovranucleus) is laid above. The rudus acts as a gradient between the statumen and the sovranucleus.”

The text was amended following the reviewer’s suggestions.

 

Line 57: “allow differentiating” (not “allows differentiating”)

Corrected

 

Line 73-74: “..dated to the fifth and the first half of the sixth…”. Better to say: “…dated between

the fifth and the first half of the sixth..:”

Corrected.

 

Line 98-99: Better to say: “We characterized chemically and structurally…”

The text was amended.

 

Line 117-118: “Samples and location of measurements are shown in fig. 2”. Figure 2 reports the samples, but not the location of measurements.

The text was amended.

 

Line 223: “showing that” and not “showing of”

Corrected.

 

Line 239: “Petrographic analysis of the sinopia shows THAT the substrate…” Corrected

Line 252: “contain”, not “contains”

Corrected

 

Line 282 (Caption fig. 7): I suppose that the correct caption is “…rudus mortars below (A) black and (B) red areas”, not (C) red areas, since (C) is referred shortly after to the red sinopia.

Corrected

 

Figure 8: In the Raman spectrum of S_RB, I would shift the label “Calcite” above the main calcite peak at 1082.

Corrected

Line 307: “showing THAT…”

Corrected

Line 330: “…indication OF the high level…” better than “indication TO”

Corrected

Line 345-351, and figure 9: I do not understand why the authors speak so much about Lod mosaic and its footprints, showing even a figure…I do not see a connection with the present archaeometric study…

Figure 9 was removed. The text explaining the importance of the preserved features in the mortars below the mosaic is in line 378-381: “these underlying contexts may preserve delicate features from chemical alterations and bioturbation, as a protected niche that preserves organic molecules and other information [40], since they are protected by the mosaic stone tesserae.

 

 

Line 355: “that preserveS”

Corrected

 

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

I have read the paper 'Mosaic Technology in the Armenian Chapel Bird Mosaic, Jerusalem: Characterizing the Polychrome Hidden Sinopia' by Yotam Asscher, Giulia Ricci, Michela Reato, Abraham Leviant, Ilana Peters, Jacques Neguer, Mark Avrahami, and Gilberto Artioli. The paper presents compositional data obtained through various methodologies on a polychrome sinopia found beneath a Byzantine mosaic in an Armenian chapel in Jerusalem. Although the research does not introduce particularly original aspects, it can still provide valuable information about the pigments and techniques used during the creation of the mosaic. It is, therefore, a case study that, as stated by the authors, confirms a Vitruvian procedure.

The text needs to be clearer in some parts, as certain concepts are assumed to be understood and require better explanation. I am quite perplexed by the use of various analytical techniques that do not provide additional information (e.g., pXRF). Moreover, some figures are too small to read, and the tables need to be presented more accurately.  I have included some comments in the text and highlighted, as examples, parts that need to be modified or corrected.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The English  needs extensive revision.

Author Response

We thank the reviewer and all of the comments were addressed and accepted in the main revised text