Principal Component Analysis (PCA) Combined with Naturally Occurring Crystallization Inhibitors: An Integrated Strategy for a more Sustainable Control of Salt Decay in Built Heritage

Round 1

Reviewer 1 Report

The topic is very interesting and the research carried out is precise and rigorous.

However, as it is evident that this paper is only a part of the whole work, the structure needs to major revision. The reader should be able to understand the scientific materials and methods employed clearly. The use of PCA is the main aim in this paper but the explanation of this metod is in the introduction and not in a dedicated caption.

The title: “An Integrated “Clean” Strategy for Salt-Induced Decay Control in Built Heritage Based on Naturally Occurring Crystallization Inhibitors” is not the main focus of this paper. In this paper you don’t’ speak about the real results obtained using Naturally Occurring Crystallization Inhibitors but you analyse with statistical method (PCA) the data of literature. I think that the title must be change.

 

Line 28 -31 Simplify the sentence

Line 31- 37 divide the period: ”Salt decay is generally understood as a temperature/humidity dependent weathering process arising from the presence of salt crystals on the surface of porous materials including natural stone, which generally results in in aesthetic rather than mechanical damage (i.e. efflorescence) in aesthetic damage  in little damage, though is often impressive and highly visible, or from mechanical stresses introduced by salt crystals deposited within the material pores (i.e. subflorescence or cryptoflorescence), which may ultimately endanger the structural safety of the materials as well as cause widespread loss of (sometimes precious) surface.

Line 50: “thus keeping salt precipitation far from occurring” simplify with “therefore salt precipitation”

Line 53, 56, 69, 74 and 75  The text needs to be objective and in third person. To achieve this it needs to be avoided using personal pronouns. The same for all other sentences in the paper (i.e. line 116 etc.)

Figure 2 is not necessary is not a result of work, it is literature data

Line 115 This is Material and Methods caption is necessary move here the samples used and also the Introduction of PCA approach that you use in the data analysis. Remove the parts with such arguments from the introduction and leave in the latter only the main summary of the paper.

Line 116 not necessary introduce that in this caption the authors will be explain the work, it is already the Material and Methods caption

Line 117 How many blank samples?

Line 118 – 123 It is not clear, in this caption is necessary introduce the materials (That you have explain in introduction but not here) and also method: “aqueous solution of the inhibitors in question” Which? Insert also in the text or insert refer to the table. “eventually using different application methods” Which? Is not clear.

“Following the above procedure” the capillarity in a controlled environment? so the method is only one?

Line 132 (∆?⁄? in g/cm2, see above) where? There is the data? what are the other variables?  

Line 144 -146 Why?  “according to their somewhat different features”  which? describe the samples? i.e. their porosity, their chemical composition….. the samples are limestone.

Line 147- 148 the same as above, the samples are not described, for the reader is impossible to understand why there are differences.

Line 166-168 explain better

Figure 7 in the caption explain 1-2-3-4 areas

 

Author Response

The authors thank the reviewer for the suggestions for improving the comprehention of the paper.
All points have been clarified and expressed in more detail. In particular, more descriptions have been included on the Materials and Method, describing the variables, the types of samples and the conditions of their treatment. The Discussion has also been expanded and detailed to better clarify the interpretation. The title has been changed as required.
All fixes can be seen in the revised paper. 

Author Response File: Author Response.docx

Reviewer 2 Report

An interesting approach to use statistics/math for evaluation of complex data and finding explanations/directions which is clearly written and explained. The example of choice as shown in figure 8 obviously reflects the analysis of one crystallisation test, I am wondering why not all 4 selected tests from figure 7 score plot were analysed. Also, I am not convinced that, the full volume of the information of the test was analysed/used, in figure 8 two trends of the points obtained at different time intervals can be seen, namely a quickly movement along the PC1 axis and at the same time a movement along the PC 2 axis from positive to negative values (data points 1- 7). On the other side, with progressing time the last dependency (movement) seems to reverse, so I do not agree with the authors that the significant phases of each experiment are the start and the end times. I like to see a deeper reflection of these trends and possible explanations as well as a analysis of all 4 in score plot 7 selected tests.

Author Response

The authors thank the reviewer for the suggestions for improving the comprehention of the paper.
All points have been clarified and expressed in more detail. In particular, more descriptions have been included on the Materials and Method, describing the variables, the types of samples and the conditions of their treatment. The Discussion has also been expanded and detailed to better clarify the interpretation. Also the title has been changed for more specificiation.
All fixes can be seen in the revised paper. 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Dear Authors, 

Insert the caption to the Table 2

Correct in the test Figure 6 with Figure 7 

The caption of Figure 8 is wrong:"Figure 87. Loading Plot of the independent variables."

There are some points where the punctuation at the end of the paragraph is reversed. To check. 

 

Author Response

Thank you for your suggestion. All correction were done