Scientific Study of the Origin of the Painting from the Early 20th Century Leads to Pablo Picasso

Round 1

Reviewer 1 Report

The manuscript titled “Multidisciplinary study of the origin of the painting from the early 20th century leads to Picasso” presents a clear and detailed discussion on the origin and chemical analysis of the Red Guitar painting. Through a series of historical evidence with regards to the history of the work of art, followed by the application of several important analytical methods such as X-ray radiography, X-ray fluorescence spectroscopy, FTIR and raman spectroscopy. The scientific evidence is carefully analysed and compared to literature studies or information from crucial databases with regards to Picasso’s earlier works. Finally, a conclusion is postulated, suggesting that the Red Guitar work of art is indeed an original work and not a copy of another, similar, work by Picasso.

The manuscript is generally well written, aside from some grammatical incorrect sentences that could do with revision. The work is well-structured and well-argumented. The figures could do with some enhancement, particularly the XRF spectra axis and peak labels are consistently illegible when observing them at the  intended manuscript size.

As such, I strongly encourage the publication of this manuscript, provided some minor corrections or alterations as indicated below:

Title: “ Multidisciplinary study of the origin of the painting from the early 20th century leads to Picasso” -> It is at this stage rather unclear to the unfamiliar reader what the importance of Olga Picasso’s biography is to the red guitar painting, and may even confuse the reader to think that the red guitar painting was painted by Olga instead of Pablo. Consider revising.

Abstract: 2^nd sentence: “Furthremore” -> Furthermore (in light of previous comment, it may be advised to replace Furthermore by ‘Additionally’, which conveys better what the authors probably intended.)

Keywords: ‘Red Guitar’ and ‘Picasso’ are not listed as keywords, even though these would be quite clear search terms when looking for this manuscript (or any information on this work of art in general). Perhaps it can be considered to add these keywords, perhaps in exchange for perhaps less specific keywords such as ‘colorants’ or ‘nitrocellulose’

P3, 2^nd paragraph: “NIkolaj” -> Nikolaj

P3, 2^nd paragraph: “a painting changing hands from Picasso to Hadzic family” -> (…) to the Hadzic family.

P3 2^nd paragraph: “Red Guitar waspart of this particular event” -> was (a) part of

P5 1^st paragraph: Font size suddenly appears significantly larger than surrounding front. Is this one purpose or a stylistic oversight?

P5 2^nd paragraph: “the X radiography” -> X-ray radiography

P5 2^nd paragraph: “The digital X-ray images are formed on the principle that a low density area experience higher radiation exposure and, therefore, produce darker shades, while more dense areas are less exposed and pro-duce lighter shades on the images.” -> this is not entirely true. The difference is shading is not caused by differences in exposure (or at least, it shouldn’t be caused by this). The difference originates from the low density regions absorbing less X-ray photons (for a given unit of depth or sample volume) compared to the high density regions, which absorb more photons. The exposure on each region should be identical, or if this is not the case the acquired transmission signal should be corrected for the appropriate photon exposure.

P5 2^nd paragraph: “200S (SPPED” -> is the 200S short for 200 seconds? If yes, the s should be lower case. Additionally, SPPED is not a familiar acronym for a wide public and thus should be written in full at first usage of the term.

P5 section 2.2: “Furrier-transform” -> Fourier-transform

P5 section 2.2: “4000–225 cm–” -> cm^-1

P5 section 2.3: “Technique simultaneously detects C, H, N, and S” -> This technique (…)

P5 section 2.4: “micro x ray tube” -> X-ray

P5 section 2.4: “Silicon Diode Detector(SSD).” -> The acronym is probably SDD, which stands for Silicon Drift Detector (not diode, although it is a type of diode as well of course)

P6 section 2.4: “It was operated at 45 keV and 30 μA using a red filter (Ti, Al, Cu) without vacuum” -> in XRF it is not particularly important which colour a filter has, as X-rays are of a different wavelength than optical light and thus are not absorbed or reflected based on (optical) colour. More interesting would be to provide a filter thickness, and weight fractions of the mentioned elements contained within the filter material.

P6 section 2.4: “the signal to nose ratio” -> signal to noise

P6 section 2.5: “with LabRAM” -> with a LabRAM (…)

P6 section 2.5: “Nd:Yagr” -> is the ‘r’ here on purpose? What does it indicate? Additionally, YAG is an acronym and thus should be written in capitals (Nd:YAG)

P6 section 2.5: “with a spectral resolution 4 cm^-1.” -> resolution of 4 cm^-1.

P6 section 2.5: “The recorder spectra” -> recorded

P6 last paragraph: “The bottom area of the X-ray image is white and not very informative (Suppl. Fig. 5S).” Can the authors provide an explanation as to why the bottom area is less informative? Were higher density pigments used in painting this part of the painting? Or are the painting layers thicker in this region? Or was there another, perhaps instrumental, reason why the bottom of the painting provided lesser results?

Figure 4: The peak  and axis labels in figures a and d are hardly legible. Please enlarge the respective fonts to allow for more straightforward comparison of the spectra.

P7 last paragraph: “Although the FTIR spectrum of the leaked white paint was over-whelmed with calcium carbonate (Fig. 4c)” -> The sentence refers to the FTIR spectrum, which is displayed in figure 4b

P9 top paragraph: “If something had been subsequently changed, the XRF analysis would show differences in paint composition in altered and original areas” -> It should be noted that XRF spectroscopy only has a limited depth from which information can be obtained. As such, it is not entirely impossible that a sub-surface layer consists of different elemental composition, yet when covered by another compositional layer the resulting XRF spectrum may represent only or mainly the top layer. For absolute certainty on the statement made, the authors should in principle have removed the top layer of the painting to uncover the initial drawing and investigated this layer alone, or could have made use of a so-called confocal detection scheme where information from the subsurface is analysed selectively. Perhaps the authors can rephrase their conclusion to incorporate this uncertainty?

Figure 5: The peak  and axis labels in figures a and d are hardly legible. Please enlarge the respective fonts to allow for more straightforward comparison of the spectra.

Figure 5 caption: “The spectra were shown as semi-log plots of counts vs. energy. Various spots were represented in different colors.” -> semi-log is not a commonly used expression. Additionally, the tick marks on the y-axis of the plot make it clear that an (appropriate) log scale was used. Additionally, the last sentence should be rewritten to something along the lines of “Various spots were investigated to represent each color.” To better bring across the authors’ intent in a grammatically appropriate way.

Figure 6: Again, the figure’s peak labels are illegible. Similarly, the photograph’s scale bars are not legible either.

Figure 8: Please enhance the XRF curves to increase the legibility of the peak and axes labels.

Figure 8 caption: the caption text appears to run over into the manuscript text (probably an issue arose due to the insertion of the url link within the caption)

Figure 9: as in other figures, please enhance the peak and axes labels

P14 1^st paragraph: “Additional two signals” -> Additionally, two signals (…)

P15 1^st sentence: “showing a different product process” -> production process

Figure 10, 11: similar as for other figures.

P17 1^st paragraph: “was widely used at the end of 19th and early 20th century” -> (…) at the end of the 19^th and early 20^th century.

P18 last paragraph: “it has been applied alone or in a mixture with calcium carbonate in the surface layer where provided a ‘milky’ effect around the main composition.” -> (…) surface layer, resulting in a ‘milky effect’ (…)

P20 conclusion, final sentence: “Therefore, the multidisci-plinary approach to the analysis of Red Guitar gathered sufficient evidence and arguments to prove that this painting is Picasso’s original.” -> Although the presented scientific evidence is indeed sound, it is perhaps more prudent to not state without uncertainty that this painting is an original work by Pablo Picasso. This sentence could easily be modified to introduce a certain degree of uncertainty, which is always present in these kinds of work: “”(…) evidence and arguments to prove that this painting is likely a Picasso’s original.”

Author Response

Response to Reviewer 1

Thank you so much for your advice and comments.

We accepted your constructive criticism and made corrections as per your suggestions.

1. We adopted a new title: “Scientific study of the origin of the painting from the early 20^th century leads to Pablo Picasso”
2. We prepared new XRF spectra and figures
3. We added new keywords: Red Guitar and Pablo Picasso
4. P3, 2^nd paragraph is corrected
5. P5 1^st paragraph is corrected
6. P5 and P6: 2.2.-2.5, P7
7. All typing errors were corrected.
8. The acronym “SPPED” is deleted- since we could not find more information about it.
9. The explanation for the use of the word ‘red’ XRF filter could not be found and likely only represents the filter label. The word ‘red’ is now deleted. We could not find additional technical information about the XRF filters.
10. P6 last paragraph:

To clarify that the bottom  X-ray area is  less artistically  informative ( Suppl Fig 5), we changed the sentence to:

 ‘The bottom area of the X-ray image did not show significant compositional changes (Suppl. Figure 5S)” . to clarify that there were no technical /instrumental reasons involved.

11. P9 top paragraph is adapted based on your suggestion:

“….If something had been subsequently changed, the XRF analysis could indicate differences in paint composition in altered and original areas [10]. However, due to a limited depth of XRF detection, it is not entirely impossible that the subsurface layer consists of different composition from the surface layer.”

12. The peak and axis fonts are enlarged in all figures; Figure captions are changed as suggested.
13. P14 1^st paragraph and sentence were corrected as suggested.
14. P17 1^st paragraph, P18 last paragraph, and P20 conclusion-final sentence were corrected as suggested.

Reviewer 2 Report

See file.

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 2

Thank you so much for your comments and suggestions. We now include the changes you suggested:

1. Pigment names are not capitalized.
2. Abstract: the word ‘genuine’ is changed to ‘authentic’
3. The title is changed to “Scientific study of the origin of the painting from the early 20^th century leads to Pablo Picasso”.
4. We separated the XRF elemental analysis from the organic elemental analysis.
5. Generally, based on the type of instrumentation used the spectra were additionally explained in Figure captions and text and have been balanced in an accord with described literature.
6. Conclusion: we added ’provides proof’
7. Page 13 Figure.8 is completed, and Page 18, 20 fonts are corrected.
8. References: they are now according to the journal requirements.
9. Figures 2-5 are all corrected.
10. Sec 3.3. and Sec 3.7 are corrected.

Reviewer 3 Report

I read the paper titled "Multidisciplinary study of the origin of the painting from the early 20th century leads to Picasso"

I found the research interesting, because provide a new opportunity for scientist involved in painting characterization through multi analytical approaches and involves studies on a Picasso painting.

The paper is well written and the goal is focused and well realized by a proper description both of the technique and data interpretation.

The manuscript is potentially interesting for the readers of Heritage. As a reviewer, I still have some comments and suggestions.

1.            Please improve the introduction by explaining the importance of multi analytical approaches for the study of pigments. found some examples in the following papers The emergence of Liu Kang’s new painting style (1950–1958): a multi-analytical approach for the study of the artist’s painting materials and technique, How many secret details could a systematic multi-analytical study reveal about the mysterious fresco trionfo della morte? Authentication of a Painting by Nicolae Grigorescu Using Modern Multi-Analytical Methods Multi‐analytical non‐invasive study of modern yellow paints from postwar Italian paintings from the International Gallery of Modern Art Cà Pesaro, Venice

The identification of all pigments can be supported by the comparison with databases describing the main features for the identification and the best techniques to use, authors should improve the result section by discussing the databases in literature and the approaches for the identification of pigments. I suggest citing the following papers:

Chemometric tools to point out benchmarks and chromophores in pigments through spectroscopic data analyses, Historical pigments: a collection analyzed with X-ray diffraction analysis and X-ray fluorescence analysis in order to create a database, FTIR Spectra Database 2003 / ANALYTICAL CHEMISTRY 215 A, FORS spectral database of historical pigments in different binders, On-line FT-Raman and dispersive Raman spectra database of artists' materials (e-VISART database)

2. Authors should explain the average amount of the sample needed for the measurement and the relative sampling for FTIR measurements

3.            Please improve the quality of the graphs, scales labels are barely legible, and correct the axes label of FTIR measurements (y = transmittance, x = wavenumbers) moreover standardize the text format (in some cases the size change).

4       Please double check the references some names are reduced while others not

Author Response

Thank you very much for your comments and suggestions. We greatly appreciate your time and efforts.

1. Regarding your first suggestion, our Introduction already contained 6 pages. Our main goal was to describe the historic evidence for this previously unknown and uncharacterized painting, and for which we found that the historic evidence is the most important to provide. The Introduction was widely approved by the other two reviewers.

Furthermore, that the identification of pigments can be supported by the comparison with databases is completely accepted. We have indeed used and cited several spectral databases that were the most directly related to our specific information and compounds found, such as Pigment Checker, SOS pigment specific database as well as CAMEO art database. We also used up-to-date specific reference papers for the cellulose and nitrocellulose FTIR since we could not find them of sufficient quality in the art databases. We, however, did not use X-ray diffraction and FORS in our work nor did we use eVISART.

2. Regarding the FTIR sampling, we added the following information: “We analyzed the paint samples as-is without preparation. From the leaked paint and from the back area after the varnish and paint layer were separated, we prepared a minimum of 100 mg of sample to cover a 3-mm circle area and to produce multiple measurements.”
3. We have greatly improved the quality of the graphs and corrected the axes label of FTIR
4. We standardized the text and references as per the publisher’s recommendations