Review Reports - “A Woman Clothed with the Sun”: The Diagnostic Study and Testing of Enzyme-Based Green Products for the Restoration of an Early 17th Century Wall Painting in the Palazzo Gallo in Bagnaia (Italy)

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

- This is an interesting case study about an 17th century wall painting, investigations techniques (traditional and modern) and restoration interventions.

Comments for author File: Comments.pdf

Author Response

Reply to reviewer #1

Dear reviewer thank you so much for the revision work.

I checked the figures and I corrected according to your indication.

301 finishing layer: corrected

400 to precise here the chemical composition of Dowanol PM: I added the information about Dowanol PM and also a reference explaining better the characteristics of this solvent, thank you for the comment

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article entitled "A woman clothed with the sun": diagnostic study and texting of enzyme-based green products for the restoration of an early 17th century wall painting of Palazzo Gallo in Bagnaia (Italy), presents the attempt to recover this mural painting which was previously intervened in a very inappropriate manner. In a first phase of the work, the original materials and those used for its restoration were identified using optical microscopy on micro-stratigraphic sections, X-ray fluorescence spectroscopy and Fourier transform infrared spectroscopy. In the second phase, an attempt was made to eliminate the remains of the consolidating materials used in the restorations using enzyme-based green products.

The article assesses the suitability of the products according to the state of conservation of each of the areas of the mural painting.

The topic is of great interest. The use of gels and enzymes for cleaning mural painting is a topic of great interest for study due to the possibilities it offers. This is a still new field where restorers need scientific evaluations of the actions.

Some improvements that the authors could include in the manuscript are the following:

-Figure 2. The font size of the legend text is very small and of low quality. It is recommended to improve it. Grouting type 1, 2, 3 and 4 must be defined in the text.

-Figure 3. Point 6 is missing. Point 8 is duplicated.

-Table 2. In the table, the elements identified as majority must be marked.

- Points X10, X11 and X18 "red": Pb has been identified. How is the presence of this element justified? Could it be minium red + cinnabar ?

Author Response

Authors reply: dear reviewer, thank you so much for your positive evaluation of our paper and for the punctual comments about the various parts of the manuscript.

References 16 has been corrected, according to the indication.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors The authors focused on a 17th-century mural painting of the Virgin between two saints from the Renaissance palace Palazzo Gallo in Bagnaia (Viterbo, Italy), which was restored in 2021. It was scientifically investigated with techniques traditional characterization methods (optical microscopy on micro-stratigraphic sections, X-ray fluorescence spectroscopy and Fourier transform infrared spectroscopy) which allowed the identification of both the original pictorial materials and those used in the restoration. Also by fluorescence in ultraviolet and micro-mapping through the hypercolorimetric multispectral imaging technique (HMI) allowed the assessment of the state of conservation, the localization of restoration interventions and supporting the monitoring of the cleaning interventions of the protective layer based on Paraloid, applied in the early 2000s, which over time affected the iconographic system , making it unreadable. Based on this data, a restoration protocol based on environmental sustainability and green was made chemistry, enzyme-based gels that have been tested in various paintwork cleaning protocols. Although some results were interesting, a reduced efficiency of enzymatic cleaning was observed in comparison with traditional chemical solvents, such as Dowanol PM (methoxy-propanol) and benzyl alcohol.

The subject is interesting, the border is original.

I am very pleased with the value of the work, which I find attractive for the journal.

The specialized literature was well selected, and the critical analysis of the 36 references (of which 23 can be found in the analysis of the current state of knowledge presented in the Introduction) it is well done.

Materials for experiments and work methods are rigorously selected from the group of modern working techniques.

The figures/graphs and tables are very well done.

The interpretation of the experimental results corresponds to the agreed level of the journal.

As for the conclusions of the work, they are well developed, being representative.

The bibliographic references (36) are rigorously selected from the current specialized literature.

The paper can be published after correcting reference 16. Last author from reference 16 (Pereira, C.; Busani, T.; Branco, L.C.; Joosten, I.; Anca Sandu, I.C. Nondestructive characterization and enzyme cleaning of painted surfaces: assessment from the macro to nano level. Microsc. Microanal. 2013, 19, 1632-1644) is written incorrectly, it should be written: Pereira, C.; Busani, T.; Branco, L.C.; Joosten, I.; Sandu, I.C.A. Nondestructive characterization and enzyme cleaning of painted surfaces: assessment from the macro to nano level. Microsc. Microanal. 2013, 19, 1632-1644.

Author Response

Dear Reviewer,

Thank you so much for your work of revision and for te positive evaluation of our paper.

We replied points by points to your comments and suggestions (see below).

Dear authors,

The manuscript is interesting and well organised however some minor issues are given below:

- In the abstract: please delete the name of the compnies for the restoration prodcuts.

Authors reply: I checked the introduction but I did not find the name of the companies. Probably the reviewer is referring to Paraloid B72, Acryl AC33 and Primal that are the commercial name of the products used in the past restoration and widely in the literature. I changed the text to better highlight this. The company that produced Paraloid and Primal is Rohm and Haas or one of its subsidiaries or affiliates.

- In the introduction section: I prefere to seperate the paragraphs concerning the studied object under a subtitle ' the studied case study'

Authors reply: we divided the Introduction into three sub-paragraphs named: 1.1 The case study; 1.2 The conservative history and 1.3 The aims of the present research.

- please change the word 'mortar' to 'plaster or render layer' in the whole text.

Authors reply: done

- For XRF results, are some elements related to the instrument itself?

Authors reply: no, all elements reported in the Table 1 are detected in the wall paining

- could the detection of cobalt and arsenic in the smalt blue reflect the used cobalt ore in the prodcution process?

Authors reply: The presence of Co, As and Ni is associated to the minerals used for producing blue smalt such as smaltite (in the Middle Ages) and later erythrite and cobaltite (in the seventeenth and eighteenth centuries). According to some authors, the presence of bismuth associated to Co, As and Ni suggests that the minerals came from the Erzgebirge mines in Saxony that can be supposed the origin of the materials used for our smalt.

We added this part in the manuscript and also some references to support our assessment.

- For the green pigment, could it be a mixture of smalt and orpiment? and the same for the yellow pigment a mixture of yellow ochre and orpiment?

Authors reply: according to our opinion this not the case. In the green areas we found iron and also in the yellow ones. The presence of As in correspondence of some green and yellow areas could be traced back to the use of very small amounts of blue smalt blue (in which cobalt, nickel and bismuth would be in quantities lower than the detection limits of the instrument in the configuration adopted), or to an impurity of this element in some earths, or to the use of orpiment and/or realgar. This last hypothesis, however, seems rather unlikely, as the counting rate of the photons relating to the arsenic is so low that it is not sufficient to provide a chromatic contribution to the colour. Arsenic contamination could also be attributable to residues from sanitization treatments of wooden elements, such as those on the ceiling of the room.

- Authors should eliminate the use of compinies name and to use the chemical formulas of prodcuts instead.

Authors reply: the names reported (Paraloid B72 and B44) are not that of the companies but they are the names of the commercial products. These names are well-known and are reported in the literature and in the spectral databases. Anyway, we added the names of the polymers and some references concerning study and characterization of such acrylic resins

-Also, as authors stated that the cleaning products did not give sufient reulst, how they performed the cleaning process succesfully?

Author reply: the cleaning was successfully performed by using benzyl alcohol and Dowanol PM. This last is a low toxicity solvent based on propylene glycol monomethyl ether that revealed effective in removing the surface materials added in the 2003-2004 restoration. We added some information on Dowanol and a reference to support its use and to know its characteristics.

Comments on the Quality of English Language

some grammatical errors should be corrected

Authors reply: English language has been carefully checked and some errors have been corrected. Thank you for the comments

Author Response File: Author Response.pdf

Reviewer 4 Report