Papier-Mâché Puppets’ Characterization by Infrared Imaging Techniques

Round 1

Reviewer 1 Report

The proposed article presents good results of the applicability of two innovative techniques for the study of cultural heritage objets. The article also discusses the restoration procedures based on the results obtained. .

Author Response

Thank you for the revision

Author Response File: Author Response.docx

Reviewer 2 Report

Manuscript ID: heritage-1776605

Type of manuscript: Article

Title: Papier-mâché puppets characterization by Infrared Imaging techniques

1. Recommendation:

Reconsider after major revisions

2. Comments to the authors:

2.1 Overview and general recommendation

The paper "Papier-mâché puppets characterization by Infrared Imaging techniques" presents an interesting technique that allows monitoring the extension of insect galleries and evaluating the consolidation treatments in paper-based objects. Even though this work presents a specific case of study (puppets), papier-mâché was employed in the manufacture of many other artefacts, and it is related to other similar techniques (e.g., Italian cartapesta), for this reason, the results present in this work could be of interest of different audiences.

However, the work requires further improvements regarding the quality of the images and highlighting the main advantages of the methods presented.

I am confident that if the authors are willing to complement the information presented, the work will improve considerably. For this reason, I recommend to reconsider the paper after major revisions. I explain my concerns in detail below.  

2.2 Major comments

I find two main issues that require attention. The first one is related to the comparison of the MWIR and PT results with other conventional imaging techniques commonly used by the Heritage Science field (e.g., TAC, radiography, and UV imaging). Some of the features shown in this paper may be identified by other techniques, for example, previous conservation treatment by simple using UV-induced fluorescence imaging. Also, it could be interesting to support or compare the hypothesis done based on the MWIR and PT images with other traditional technique (i.e., TAC or radiography), particularly regarding the extension of the insect galleries, or evaluate the result agreement with the measurements from other techniques. This issue needs to be addressed by the authors, highlighting the advantages of MWIR and PT in comparison with other methods widely used by the Heritage community.

The second concern regards the image quality; many of the images are of poor quality and some of them are out of focus, this should be improved.

Finally, I would suggest reorganizing sections 4.2.1 and 4.2.2 by joining them since both are related to the conservation treatments and their evaluation using the two techniques. This is an interesting result from the research and should be highlighted since few methods allow for monitoring the efficacy of consolidation treatments in a fast way. Moreover, consider modifying the title since the technique does not offer a characterization – in terms of material identification – but a study, in particular, of the degradation, previous treatments and an evaluation of conservation treatments.

2.3 Minor comments

Page 2. Line 56. There is a red point after reference 15.

Page 2 Line 72. The plural of "codex" is "codices", please substitute it.

Fig. 1. The images are out of focus, please provide images of better quality.

Page 4. Line 131. There is a blue number 2.

Page 7 Line 202. "correspond to larger amounts of IR radiation" do you mean reflected? Please specify. Also, "amount" is a non-countable word thus it should be substituted by "amount."

Page 7 Line 214. There is a repetition of "(red arrows)" and a point in the middle of a phrase.

Fig. 6 The position of the image in visible light, which is also out of focus, does not correspond to the reflectogram and thermograms, which complicates the comparison. If possible, it could be better to substitute the image with a photograph of better quality and in a position similar to the one recorded in the reflectogram and thermograms. Another solution could be to associate a number to the arrows and mark the same areas also in the visible light image to make easier the association of the features highlighted.

Also in Fig. 6, caption. The decimals are divided by "," (comma), please substitute it with a decimal point. This problem appears in other sections of the paper. Besides, probably the correct term for insect's walkways is "galleries" while for the holes "exit holes."

Fig. 7 This figure is hard to interpret alone, it could be better to present it together with the visible light image and probably mark or indicate the same features in both images to facilitate the association.

Fig. 8, caption. Please revise the decimal point and the term walkways.

Page 10 Line 254. "ather" should be substituted with "other."

Page 10 Line 256. Consider substituting entomological "pathways" with "galleries."

Page 11 Line 276. Please substitute the comma with a decimal point.

Figure 12. In some areas, the thermograms show some white areas associated with insect galleries, even though the effect is reduced after the treatment, in some cases (e.g., the cheek at the right) it remains, is this associated with a partial consolidation? Please elaborate further on this respect and how this information helps conservators to evaluate the efficacy of the treatments applied.

Author Response

- I find two main issues that require attention. The first one is related to the comparison of the MWIR and PT results with other conventional imaging techniques commonly used by the Heritage Science field (e.g., TAC, radiography, and UV imaging). Some of the features shown in this paper may be identified by other techniques, for example, previous conservation treatment by simple using UV-induced fluorescence imaging. Also, it could be interesting to support or compare the hypothesis done based on the MWIR and PT images with other traditional technique (i.e., TAC or radiography), particularly regarding the extension of the insect galleries, or evaluate the result agreement with the measurements from other techniques. This issue needs to be addressed by the authors, highlighting the advantages of MWIR and PT in comparison with other methods widely used by the Heritage community.

The following sentence has been inserted in the introduction, page 2, lines 84-98: “Such an approach allowed us to obtain valuable information concerning the layered structure of the puppets by revealing structural features (i.e. the insect galleries) buried beneath the visible pictorial layer and by mapping the restorations. It is worth noticing that these aspects can be separately investigated by using different kind of techniques, such as, for instance, X-ray radiography and UV fluorescence for the detection of the insect galleries and of the restored areas, respectively. X-ray radiography enables probing the object to a depth larger than that detectable by PT, but with limitations in performing depth-resolved investigations of the artefact, since it provides a depth integrated image. Moreover, the complexity of the X-ray equipment and the involved safety issues often limit its in situ application. Concerning UV fluorescence, it can be successfully used to investigate the most outer layers of the artefacts to detect and characterize surface features like pictorial retouches and restored areas, but not features located deeper beneath the surface layers. In that regard, the use of MWIR techniques can be very useful since they enable the detection of both sub-surface and invisible surface features.”

-The second concern regards the image quality; many of the images are of poor quality and some of them are out of focus, this should be improved.

The quality of the images has been improved and all the out of focus pictures have been removed.

-Finally, I would suggest reorganizing sections 4.2.1 and 4.2.2 by joining them since both are related to the conservation treatments and their evaluation using the two techniques. This is an interesting result from the research and should be highlighted since few methods allow for monitoring the efficacy of consolidation treatments in a fast way. Moreover, consider modifying the title since the technique does not offer a characterization – in terms of material identification – but a study, in particular, of the degradation, previous treatments and an evaluation of conservation treatments.

Sections 4.2.1 and 4.2.2 have been joined and the title of the section 4.2 has been changed to “Restoration and evaluation of the conservation treatments”

- Fig. 6 The position of the image in visible light, which is also out of focus, does not correspond to the reflectogram and thermograms, which complicates the comparison. If possible, it could be better to substitute the image with a photograph of better quality and in a position similar to the one recorded in the reflectogram and thermograms. Another solution could be to associate a number to the arrows and mark the same areas also in the visible light image to make easier the association of the features highlighted.

The quality of fig. 6 has been improved. In particular, fig. 6a has been substituted.

- Fig. 7 This figure is hard to interpret alone, it could be better to present it together with the visible light image and probably mark or indicate the same features in both images to facilitate the association.

To facilitate the comparison with the thermograms and the photograph Figure 7 became Figure 6e.

-Figure 12. In some areas, the thermograms show some white areas associated with insect galleries, even though the effect is reduced after the treatment, in some cases (e.g., the cheek at the right) it remains, is this associated with a partial consolidation? Please elaborate further on this respect and how this information helps conservators to evaluate the efficacy of the treatments applied.

The following sentence has been added (page 10, line 330-332): “It is worth noticing that the possibility to detect not fully filled areas is of fundamental importance for conservators and restorers to assess the effectiveness of the adopted treatments and to plan further conservation strategies.”

-All typos have been corrected.

Author Response File: Author Response.docx

Reviewer 3 Report

Interesting paper which deserves to be published on Heritage after minor revisions as explained in the following:

- Talking about "historical facades" (to be added), authors should consider these works in the Introduction section:

DOI: 10.3166/qirt.2.5-24

DOI: 10.1080/17686733.2013.865910

- Talking about "bronze", authors should consider this work in the Introduction section:

DOI: 10.1080/17686733.2020.1799304

- Talking about "panel paintings", authors should consider this work in the Introduction section:

DOI: 10.1080/17686733.2021.2019658

- Regarding the novelty of the paper, by reading the abstract section it seems that the technique (i.e., the joint use among PT & MIR) is new ... which is not the case in my humble opinion. It is instead "new" the joint use among PT & MIR when applied to the objects under inspection. Please check and correct the meaning.

- It could be of interest to clarify in the paper the colorimetric role, in the case under analysis, of the colored strip put at the bottom of Figs. 1a, 2a, ....

- It could be of interest to clarify in the paper the precautions taken in the moving of artworks from the "Museo delle Civiltà" to the Laboratory where the IRT inspections were performed.

- Typos are present in the paper, e.g.: "afer 2 s the"; "by the naled eye"; "In tis section"; "Museo delel Civiltà".

- Please specify the "edge detection algorithm" used in the paper.

- Talking about "edge detection algorithms", authors should consider these works in section 4.1:

DOI: 10.1080/17686733.2020.1819707

DOI: 10.1080/17686733.2018.1426137

- In Figs. 9 (c&d) I suggest replacing the solid green arrows with dotted green arrows.

- I suggest replacing Ref. [50] with this one: 

DOI: 10.1080/17686733.2016.1200265

which fits better with the concept expressed by the authors.

Author Response

-  Regarding the novelty of the paper, by reading the abstract section it seems that the technique (i.e., the joint use among PT & MIR) is new ... which is not the case in my humble opinion. It is instead "new" the joint use among PT & MIR when applied to the objects under inspection. Please check and correct the meaning.

The sentence has been changed to: “In this paper, a method based on the combined use of Pulsed Thermography (PT) and Mid Wave Infrared Reflectography (MIR) is, for the first time, proposed for the characterization of papier-mâché artworks.”

- It could be of interest to clarify in the paper the colorimetric role, in the case under analysis, of the colored strip put at the bottom of Figs. 1a, 2a, ....

The colored strips have been removed.

- It could be of interest to clarify in the paper the precautions taken in the moving of artworks from the "Museo delle Civiltà" to the Laboratory where the IRT inspections were performed.

The puppets were transported inside the conservative boxes protected with conservative tissue paper and pluriball.

- Please specify the "edge detection algorithm" used in the paper.

The algorithm is Sobel edge detection of MATLAB2020b suite (page 8, line 242).

-All typos have been corrected.

- All the references indicated by the referee have been added.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The authors have considered all the previous suggestions and modified the manuscripts accordingly, which helped to improve the paper.