Aesthetic Effects on Granite of Adding Nanoparticle TiO₂ to Si-Based Consolidants (Ethyl Silicate or Nano-Sized Silica)

Round 1

Reviewer 1 Report

The paper reports an interesting experimental work on the compatibility of two commercial silicone treatments (Estel 100 and Nano Estel) doped with titania nano particles used for the conservation of granite surfaces. The research focuses on the esthetical variation of granite comparing the chromatic alteration of the stone surfaces and its morphology before and after the treatment. The paper is well written; however, some major revisions could improve the scientific relevance of the work.

My general comments on the paper of J. Santiago Pozo-Antonio et al. are reported in the following:

INTRODUCTION:

Line 37: the aim of consolidation treatments is not well explained. The application of a consolidant is due to improve the cohesion of a stone surface, slow down its natural deterioration […] and not only to diminish the effects of deterioration agents. The latest could be also confuse with the goal of the application of a protective product.

Please, improve your explanation.

From 44 to 48: The authors limit the causes of cracking phenomenon of silicone resin to the result of the high capillary pressure in the gel during the drying. However, from the literature, it is well known that the cracking is also due to the evaporation of the solvent upon the gelification process, or in the case of products based on TEOS, to the TEOS/organometallic catalyst ratio. Please, explain better and add proper references. Lines 49-50: In which way nanoparticles should avoid cracking? Line 92: Please, correct TiO₂

MATERIALS AND METHODS:

Line 106: Since the authors applied a nanoparticles consolidant, the average pores radius and pores distribution of Rodas granite should be reported, in order to evaluate the possible penetration of the consolidant in the stone. Lines 142, 154: pay attention to the text formatting Line 145: the verb in the principal sentence is missing: Estel 1000 is composed of … From line 178 to line 181: this sentence is redundant at this point of the paper. This concept could be explained eventually in the introduction. Have the colour measurements been acquired in the same point before and after the treatments?

RESULTS:

In general, the evaluation of stone modification due to the application of the conservative treatment is limited to the aesthetical point of view. More analytical tests could improve the scientific value of the paper giving fundamental information for a scientifically-guided conservation treatment. In particular, the authors could better clarify the effectiveness of the consolidation treatments in terms of penetration depth for example. Moreover, the authors could enhance the capacity of water absorption on the samples before and after the application of the treatments, in order to monitor eventual variation.

The superficial patina is due to an excessive amount of products applied or to a failed penetration of the products in the stone? Figure 6 shows a worse micro-craking on the sample surfaces treated with Nano Estel than Estel 1000. This is not in line with Mosquera et al [4], Zendri et al. [7]. The authors should explain better this point. Line 294: Please, correct the capital letter at the beginning of the sentence

DISCUSSION:

Line 386: please correct the word consolidantes in consolidants.

CONCLUSIONS:

Line 404: Please, correct TiO₂

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

See attached review report

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors made efforts to address the remarks previously reported. However, I suggest to rewiev English language and style.

Reviewer 2 Report

Comments to reviewed report

Aesthetical effects on granite of adding nanoparticle TiO₂ to Si-based consolidants (ethyl silicate or nano-sized silica)

The comments in the review report have been incorporated into the text by the authors with particular carefulness. Especially positive to note is the fact that additional specimen preparations (polished cross sections) of the treated specimens and their SEM results were included in the work!

With regard to point 12) of the review report, there was obviously a misunderstanding: this refers to the observation of the penetration behavior and curing rates of the consolidants and not of ethanol. This could possibly be included in future research by visual observations and gravimetric measurements.