Laboratory Assessment of Selected Protective Coatings Applied on Two Sandstone Types
Round 1
Reviewer 1 Report
Dear Authors,
The topic about the use of hydrophobic coatings in the preserving integrity and beauties of historical buildings is much relevant and interesting.
In this contest the manuscript, dealing with the proposal to apply hydrophobic commercial coatings to reduce the water absorption of stones, seems interesting.
However, in my opinion the manuscript could be improved. In the following the suggested revisions.
Introduction: Please add in the introduction main results from cited references, most of all for references using common solutions as protective treatments of historical buildings.
Materials: please add a samples’ legend to use in the whole document.
Methods: please add all needed details about the employed commercial products, i.e., name, main characteristic, chemical nature, etc. The readers should be able to reproduce the experiments reported in the manuscript.
Line 122: the authors wrote: “do not form any film on the surface”: this means that the coatings are only absorbed or the surfaces are able to react with the coating, or both? Please explain in the text.
Please specify how many samples were tested for each type of coating.
Graphs in Figure 3 and in Figure 5 are not clear:
1. For each graph, it is not clear what the curves refer to. Why for each type, there are many curves? Please add legend and description in the test.
2. Which curve for each set of data is compared in the comparative graph? Please explain in the text.
3. Please compare results with the state of the art
Discussion: please add a clear comparison between the main results of this manuscript and the state of the art. The comparison must be done among the solutions adopted by the authors and similar solution found in literature. The main compared results must be then discussed. Essentially, the manuscript appears as a technical report, and it is not clear which is the progress of the present manuscript with respect the state of the art. Therefore, please explain the scientific progress of this work with respect the state of the art.
Conclusions: please report here only the main conclusions, without repeat all concepts already discussed in the “Discussion” paragraph.
A revision of the font uniformity and most of all of English are required.
Author Response
Response to Reviewer 1 Comments
Point 1: Introduction: Please add in the introduction main results from cited references, most of all for references using common solutions as protective treatments of historical buildings.
Response: Thank you, we added some main results from cited references.
Point 2: Materials: please add a samples’ legend to use in the whole document.
Response: Thank you for your recommendation. We added samples’ legend to tables and text, MS for the sandstone from Malé Skalky and HS for the Hořice sandstone and use it in the whole text and tables.
Point 3: Methods: please add all needed details about the employed commercial products, i.e., name, main characteristic, chemical nature, etc. The readers should be able to reproduce the experiments reported in the manuscript.
Response: Yes, we are aware of this slightly problematic point. But, in the interests of fairness and to avoid any complains of the manufacturers about misadvertising products indicating lower effectivity, we prefer not to provide specific product names. However, interested readers received a general information about the chemical nature in the text which allows them to find the used product on the webpage of the producer, if they really want.
Point 4: Line 122: the authors wrote: “do not form any film on the surface”: this means that the coatings are only absorbed or the surfaces are able to react with the coating, or both? Please explain in the text.
Response: Thank you for your remark, the text was replaced by following more descriptive text: “The coating is absorbed and not visible on the surface, it does not significantly change color, so do not form any film on the surface.”
In this study, we did not investigate any potential chemical reaction between paint and stone.
Point 5: Graphs in Figure 3 and in Figure 5 are not clear:
- For each graph, it is not clear what the curves refer to. Why for each type, there are many curves? Please add legend and description in the test.
- Which curve for each set of data is compared in the comparative graph? Please explain in the text.
Response: Following explanation was added directly into the text: The first four graphs in fig. 3 show the number of samples tested with one type of coating, i.e. one curve for each sample. There were different numbers of samples in each group. The last graph compares the mean, i. e. representative curves from those four sample groups, it means, it compares the different coatings.
- Please compare results with the state of the art
Response: Answer to this question is included in the response to the point 6.
Point 6: Discussion: please add a clear comparison between the main results of this manuscript and the state of the art. The comparison must be done among the solutions adopted by the authors and similar solution found in literature. The main compared results must be then discussed. Essentially, the manuscript appears as a technical report, and it is not clear which is the progress of the present manuscript with respect the state of the art. Therefore, please explain the scientific progress of this work with respect the state of the art.
Response: We are thankful for all constructive remarks. We added to discussion: “The state of the art in this field is, that there are many different hydrophobic products available on the market that can be applied to natural stones and are used in research reports applying very different test conditions and materials for the treatment ( Soulios et al., 2020, Bao et al. 2020, Hansen et al., 2018, Zhao a Meissener, 2017). Already the curing time is different. Therefore, the results are very difficult to compare to published papers due to the number of coats and also the diversity of stones. Our current research shows that the curring time of the coating is the main impact factor of the coatings´ effectiveness. In the presented research, a curing time of 2 days was chosen to find out how the coating behaves after such a short time and if it is sufficient. So, the results cannot be compared to works where authors used curing time of 2 weeks or longer. ” We also tried to explain this fact in the discussion text: “Good absorption and sufficient hardening time are crucial for the efficiency and longevity of the coating. None of the producers gives strict advices about the necessary hardening time. Producer of coating F recommends 5 h of hardening with rain disclosure to reach the optimum impregnation. Experience of paper authors proved this is too short. On the other hand, Soulios et al. (2020) reported 2 weeks are necessary for hardening. In the practice, it is impossible to control the occurrence of rain, and such a long dry period is a question of luck. Two days of hardening were chosen for the laboratory tests as a compromise. However, deducing from the high water absorption by the impregnated MS, even 48 h of hardening are insufficient. Though laboratory samples can be much better impregnated than real buildings and laboratory based applications produce generally better, more reproducible results than field based studies (Young et al., 2003), laboratory experiments with 2 days of hardening did not perform high efficiency. ”
Point 7: Conclusions: please report here only the main conclusions, without repeat all concepts already discussed in the “Discussion” paragraph.
Response: Thank you for you recommendation. We changed the conclusion and did not repeat the information addressed in the discussion.
Point 8: A revision of the font uniformity and most of all of English are required.
Response 8: We revised the font uniformity and corrected the English grammar.
Many thanks for the reviewer’s suggestions.
Reviewer 2 Report
The reviewer thanks the authors and editors for the opportunity to review the manuscript.
This article discusses issues with protecting rock from water using hydrophobic substances. This is an important issue and aims to protect the stone from early deterioration.
General remark: only 2 sandstones and 3 preparations were analysed in this study. It should be emphasised that the structure and composition of the rock also have a significant influence on the range of effect of the preparations (apart from the chemical components of the preparations). Therefore, the results obtained in the present article may not necessarily be reflected in other types of stone. It should be emphasised in the paper that this is preliminary research and further extensive studies should be conducted using a larger set of rocks.
Detailed comments:
Table 1: The authors could add pictures of the tested stones to the table.
Lines 223-225: Are the impregnated stone samples characterised by different UCS? Why was the USC not determined before freeze-thaw cycles?
Table 5: Why did the authors not examine the UCS before and after impregnation, and why did they not mark the UCS after freeze-thaw cycles?
Abstract and conclusions: In abstract and conclusions, the practical aspect of the study should be clearly emphasised.
The reviewer accepts and recommends the article for publication after minor revisions.
Author Response
Response to Reviewer 2 Comments
General remark: only 2 sandstones and 3 preparations were analysed in this study. It should be emphasised that the structure and composition of the rock also have a significant influence on the range of effect of the preparations (apart from the chemical components of the preparations). Therefore, the results obtained in the present article may not necessarily be reflected in other types of stone. It should be emphasised in the paper that this is preliminary research and further extensive studies should be conducted using a larger set of rocks.
Response: Thank you for your remark. This was a pilotresearch that will continue later on bigger sample tests. We added this information at the end of the introduction. We also added these sentences into the Conclusions: “The findings of this pilot research are necessary to optimize the future more extensive research. It should be done on more samples in particular sets, but also on other types of stones, because the structure and composition of the rock also have a significant influence on the test results. Presented data are applicable only for similar sandstones under similar test conditions.”
Point 1: Table 1: The authors could add pictures of the tested stones to the table.
Response: Done. We added pictures of the sandstones into the table.
Point 2: Lines 223-225: Are the impregnated stone samples characterised by different UCS? Why was the UCS not determined before freeze-thaw cycles?
Response: UCS for untreated samples before freeze-thaw cycles was 29.9 MPa for Hořice sandstone. We dit not test impregnated stone before freeze-thaw cycles in this research, because UCS is a destructive method that cannot be applied on the same samples before the freeze-thaw cycling and we did not expect any significant changes of UCS due to coating.
Point 3: Table 5: Why did the authors not examine the UCS before and after impregnation, and why did they not mark the UCS after freeze-thaw cycles?
Response 3: As already explained higher, impact of the coating upon UCS was not a point of interest in this study, but we have done what where it was possible. Because of a small amount of the Male Skalky sandstone, it was impossible to do these destructive tests, as we would not have enough samples for the freeze-thaw tests which were to major point of interest.
Point 4: Abstract and conclusions: In abstract and conclusions, the practical aspect of the study should be clearly emphasised.
Response 4: Thank you for your remark. Done. We added the practical aspect of the study to abstract and conclusion.
Many thanks for the reviewer’s suggestion.
Reviewer 3 Report
Lucia Dunčková et al. have tested the efficiency of three commercial hydrophobization/impregnation coatings applied on two sandstone types. Both of them are commonly building stones, which exhibit good practical application. It is novel and interest to the researchers in the related areas. I would consider the paper for publication after minor revisions are made according to the following specific comments:
- The scale bar should be given in Fig. 1,2,4,6.
- In Fig. 3, the error bar should be given.
- The test of the impregnation penetration depth are exhibited in Fig. 4, it is better to show the dynamic process for impregnation penetration. Please refer to Nano-Micro Lett. 14,97,2022
- For detail evaluating the Hydrophobic ability in Fig. 6, the corresponding water contact angle should be tested.
- For the study of wettability and its applications, the authors may refer this recent paper: Nanoscale, 2021, 13 (4), 2209-2226
- For more perfection, several language mistakes could be revised.
Author Response
Response to Reviewer 3 Comments
Point 1: The scale bar should be given in Fig. 1,2,4,6.
Response: Thank you for your remark. We added the scale into Fig. 1,2,4 and 6.
Point 2: In Fig. 3, the error bar should be given.
Response: Done. We added error bars into Fig. 3 and 5.
Point 3: The test of the impregnation penetration depth are exhibited in Fig. 4, it is better to show the dynamic process for impregnation penetration. Please refer to Nano-Micro Lett. 14,97,2022
Response 3: Thank you for your recommendation. We tried to use the simplest method for the determination of impregnation penetration depth. This pilot research is at the end now, all sandstone samples were spent, but we will be inspired by the provided article in Nano-Micro Lett. for the future, more extensive research.
Point 4: For detail evaluating the Hydrophobic ability in Fig. 6, the corresponding water contact angle should be tested.
Response: Unfortunately, we do not have the necessary equipment, a high-definition camera and relevant software, to be able to measure the contact angle. In Fig.6, we only wanted to illustrate that a drop of water does not soak into the water-repellent treated rock.
Point 5: For the study of wettability and its applications, the authors may refer this recent paper: Nanoscale, 2021, 13 (4), 2209-2226
Response: Thank you for your advice. We added the article to the Discussion and we will use it in the future research, as well.
Point 6: For more perfection, several language mistakes could be revised.
Response: Thank you for your remark. Language mistakes were corrected.
Many thanks for the reviewer’s careful check and suggestions.
Round 2
Reviewer 1 Report
Dear Authors,
thank you for having revised your manuscript according to the suggested items. In my opinion, the paper can be published.
