Performance of Iron(II)-Sulphate-Treated Norway Spruce and Siberian Larch in Laboratory and Outdoor Tests

Round 1

Reviewer 1 Report

Dear Authors.

Your study evaluates the performance of Iron(II) Sulphate treated Norway Spruce and larch in the laboratory and outdoor tests. In general, the manuscript is interesting, very well-written, structured, and informative.

I have these comments:

The main part of the experiments was carried out on Norway spruce wood. Only a closed group of the tests (solution uptake and outdoor exposure test) was carried out on larch wood. I also consider the explanation of the differences in this part between the tested wood species to be insufficient. In my opinion, this manuscript could be to deal only with Norway spruce wood.

On the other hand, overall, the abstract and the keywords correspond to the aims and objectives of the manuscript. The abstract in this form is too informative. Please, present the main findings of the article in more detail.

Lines 28,29: please change “boron” to “boric acid” and add also “quarterly ammonium compounds”.

Lines 68,69: please use concise abbreviations – e.g., “B” for boric acid and “Q” for quaternary ammonium compounds.

Lines 75-88: Explain why only a concentration of 5% was chosen for the tests with biocides.

Line 79: Table 1 (line 110) should be placed in the main text near to the first time they are cited.

Line 110: in Table 1, it is advisable to choose the order of concentration from lowest to highest. Please use abbreviations that better express the concentration used, the number 2 is used for two different concentrations – better is 2.5 instead of 2, 0.2 instead of 2, and others. The number is more suitable to be given as a subscript (for example Fe₅ B₂).

Line: 120-124: Because the short-term uptake was measured through axial surfaces, my question is, if samples were specially treated e.g., were sealed before the test for eliminating uptake through transverse direction? A graphical representation of the test would also be appropriate.

Lines 225-228: please add a new subsubsection “Statistical evaluation”.

Line 232: Please “10 seconds“ mentioned in this section and „10 minutes“ mentioned in line 85 is same?

Table 2: in table missing statistical evaluation; although it is mentioned in the text, e.g., lines 300 -310.

Table 3: in the title use “cylindrical samples “, and correct „kg/m³“.

Line 231-244: In my opinion, retention of the used solution in the case of Norway spruce wood should not be such a significant difference between rectangular and cylindrical samples. Please explain how the ratio of axial surfaces was calculated:
A/ Rectangular samples: axial surface is [(15+25)*2] * 50 = 8000 mm2, however the solution uptake is 32 kg/m3(for example for Fe – 2%)

B/ Cylindrical samples: axial surface I do not know (missing the dimension of cylindrical samples in the axial direction) however the solution uptake is 90 kg/m3 (same concentration of solution).

Lines 266-268: I recommend replacing the overview Reference 26 with the research work of sane authors Reinprecht, L., Pánek, M. (2007): Fungicide efficacy of boron in the wood preservative containing ammonium salts. Acta Facultatis Xylologiae TU Zvolen, XLIX(2): 53-62. In a discussion about change also needs to be considered the compatibility between Iron(II) sulphate and two used biocides and the effect of biocides against wood-destroying fungi due to their method of application. It is documented that the differences are when a biocide is applied as a mixture with another substance or the solution itself.  Similarly, the author addressed one in the important IRG conference paper and other works.

Lines 276-286: please discuss why the contact angle decreases with increasing iron (II) sulphate concentration. There is a lack of critical discussion about what is more suitable for the durability of wood with given substances from the point of view of the contact angle.

Lines 368-441: are missing the evaluation of the total colour difference ΔE.

 Lines 442-456: more importantly, please address more clearly the novelty and importance of the research. So that readers will know how your conclusions of the water performance studies contribute to the understanding of the durability test and weathering test (with monitoring colour changes and blue stain fungi).

References - 7 from 32 presented references were written by authors. Please, in the discussion parts of the manuscript add other research articles of other authors.

 I recommend this manuscript can be accepted for publication in the Forests Journal after a major correction.

Author Response

Dear editor and reviewer,

Thank you very much for your positive response. We appreciate the efforts of the reviewers.

We have tried to consider all the comments. However, detailed response to the reviewers is resolved below. We hope, that the reviewers will agree that the manuscript is now significantly improved, and as such suitable for publication in your respective journal. 

Reviewer #1:

Dear Authors.

Your study evaluates the performance of Iron(II) Sulphate treated Norway Spruce and larch in the laboratory and outdoor tests. In general, the manuscript is interesting, very well-written, structured, and informative.

Response: Thank you for the comment and all suggestions which helped to improve manuscript.

I have these comments:

The main part of the experiments was carried out on Norway spruce wood. Only a closed group of the tests (solution uptake and outdoor exposure test) was carried out on larch wood. I also consider the explanation of the differences in this part between the tested wood species to be insufficient. In my opinion, this manuscript could be to deal only with Norway spruce wood.

Response: All laboratory experiments were performed with was carried out on Norway spruce wood, and Siberian larch was also used for the field experiments. Siberian larch was used as a reference. Siberian larch was used because it is often used for cladding or similar purposes. In the practise we can see a lot of Siberian larch claddings whit uneven colour changes. Whit our proposed treatment new claddings can be treated. In our opinion, the use of Siberian larch in our research adds value to the manuscript. Therefore, the results of our research will be of interest not only to researchers, but also to architects, planners, and designers.

At the suggestion of another reviewer, I have added further explanation to the manuscript as to which species of wood was used for each experiment or method.

On the other hand, overall, the abstract and the keywords correspond to the aims and objectives of the manuscript. The abstract in this form is too informative. Please, present the main findings of the article in more detail.

Response: The abstract was changed according to suggestions.

Lines 28,29: please change “boron” to “boric acid” and add also “quarterly ammonium compounds”.

Response: Keywords corrected

Lines 68,69: please use concise abbreviations – e.g., “B” for boric acid and “Q” for quaternary ammonium compounds.

Response: Corrected in whole manuscript

Lines 75-88: Explain why only a concentration of 5% was chosen for the tests with biocides.

Response: Explanation was added to the text:  Only 5% of iron(II) sulphate was used in combination whit biocids. The concentration was chosen based on preliminary research, where we found that 5% iron(II) sulphate concentration optimal for the speed of colour change, final aperance of the wood and the price (data were not published).

Line 79: Table 1 (line 110) should be placed in the main text near to the first time they are cited.

Response: Table 1 was moved closer to the main text near to the first time they are cited

Line 110: in Table 1, it is advisable to choose the order of concentration from lowest to highest. Please use abbreviations that better express the concentration used, the number 2 is used for two different concentrations – better is 2.5 instead of 2, 0.2 instead of 2, and others. The number is more suitable to be given as a subscript (for example Fe₅ B₂).

Response: Table 1 corrected. We did not provide numbers as a subscript since we need the same markers in tables and graphs. Our program do not allow as to use subscript for legends.

Line: 120-124: Because the short-term uptake was measured through axial surfaces, my question is, if samples were specially treated e.g., were sealed before the test for eliminating uptake through transverse direction? A graphical representation of the test would also be appropriate.

Response: The samples were not special treated the end grains were not sealed before treatment. Explanation was added to the manuscript.  

Lines 225-228: please add a new subsubsection “Statistical evaluation”.

Response: Subsubsection added

Line 232: Please “10 seconds“ mentioned in this section and „10 minutes“ mentioned in line 85 is same?

Response: corrected in line 232 right is 10 minutes.

Table 2: in table missing statistical evaluation; although it is mentioned in the text, e.g., lines 300 -310.

Response: to the Table 2 and Table 3 statistical evaluation was added

Table 3: in the title use “cylindrical samples “, and correct „kg/m³“.

Response: corrected and statistical evaluation was added

Line 231-244: In my opinion, retention of the used solution in the case of Norway spruce wood should not be such a significant difference between rectangular and cylindrical samples. Please explain how the ratio of axial surfaces was calculated:
A/ Rectangular samples: axial surface is [(15+25)*2] * 50 = 8000 mm2, however the solution uptake is 32 kg/m3(for example for Fe – 2%)

B/ Cylindrical samples: axial surface I do not know (missing the dimension of cylindrical samples in the axial direction) however the solution uptake is 90 kg/m3 (same concentration of solution).

Response: Thank you for your remarks. Cylindrical samples had diameter 3.0 cm and high 3.0 cm Correction was made in Material in methods and in results. We made a mistake for the calculation of the volume of a cylindrical sample. Table 3 corrected. 

Lines 266-268: I recommend replacing the overview Reference 26 with the research work of sane authors Reinprecht, L., Pánek, M. (2007): Fungicide efficacy of boron in the wood preservative containing ammonium salts. Acta Facultatis Xylologiae TU Zvolen, XLIX(2): 53-62. In a discussion about change also needs to be considered the compatibility between Iron(II) sulphate and two used biocides and the effect of biocides against wood-destroying fungi due to their method of application. It is documented that the differences are when a biocide is applied as a mixture with another substance or the solution itself.  Similarly, the author addressed one in the important IRG conference paper and other works.

Response: Suggested reference was changed. Comment was thoroughly considered. Additional discussion was provided as suggested.

Lines 276-286: please discuss why the contact angle decreases with increasing iron (II) sulphate concentration. There is a lack of critical discussion about what is more suitable for the durability of wood with given substances from the point of view of the contact angle.

Response: Discussion are added to manuscript “The goal, then, is to have hydrophobic surface or contact angle on the treated samples higher than on the controls.”

and

 “Samples treated only whit iron(II) sulphate solutions of all concentrations, increase contact angle compared to control samples during 60 s of measurement. Higher contact angle means that less water will be absorbed true exposed surface. But contact angle is a surface phenomena so the data are not in line whit short or long term of water uptake.”

Lines 368-441: are missing the evaluation of the total colour difference ΔE.

Response: Graph and comments are added to the manuscript. “From the 25th week of exposure to the end of the experiment, the total colour change (∆E) was highest in the control samples for boath wood species studied. After 51 months of exposure, there were minor differences in colour between treated and untreated samples.«

 Lines 442-456: more importantly, please address more clearly the novelty and importance of the research. So that readers will know how your conclusions of the water performance studies contribute to the understanding of the durability test and weathering test (with monitoring colour changes and blue stain fungi).

Response: The Conclusions were a bit change to address more clearly the novelty and importance of findings.

References - 7 from 32 presented references were written by authors. Please, in the discussion parts of the manuscript add other research articles of other authors.

Response: Reference no. 32 Humar, M.; Lesar, B. Influence of dipping time on uptake of preservative solution, adsorption, penetration and fixation of copper-ethanolamine based wood preservatives. Eur. J. Wood Wood Prod. 2009, 67, 265–270, doi:10.1007/s00107-009-0317-1. Was changed whit Richardson, H.W. Handbook of Copper Compounds and Applications; 1997; ISBN 0824789989.

New references was added:

29. 29.

Ramos, A.M.; Jorge, F.C.; Botelho, C. Boron fixation in wood: Studies of fixation mechanisms using model compounds and maritime pine. Holz als Roh - und Werkst. 2006, 64, 445–450, doi:10.1007/s00107-006-0139-3.

No. 33

Uzunovic, A.; Byrne, T.; Gignac, M.; Yang, D.Q. Wood discolourations and their prevention with an emphasis on bluestain. Special Publication SP-50. 2008, 5–15.

And No. 34

Krpat, M.; Hubbe, M.A.; Laleicke, F. Natural, Accelerated, and Simulated Weathering of Wood: A Review. Bioresurces 2020, 15, 9998–10062.

 I recommend this manuscript can be accepted for publication in the Forests Journal after a major correction.

The revised document is attached.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear Authors,

It is an interesting and well-planned article. However, some details should be corrected in my opinion.

I present my comments in synthetic form.

Substantive comments:

Chapter Materials and Methods

At this point, it should be very clearly indicated which tests were used for Norway spruce and for which Siberian larch wood was used. e.g. the durability test against wood–destroying basidiomycetes was carried out only on Norway spruce, e.t.c.  

Chapters: Materials and Methods and Results and Discussions

In these chapters, there is no significant reference to EN 335:2013 Durability of wood and wood-based products - Use classes: definitions, application to solid wood and wood-based products. This should be completed (added) in my opinion.  

Chapter Conclusions

Here, too, it should be clearly indicated which statements apply only to Norway spruce wood and which also to Siberian larch wood.

Minor editing corrections:

Whole manuscript

The full names of the tested wood should be given. The name Norway spruce (Picea abies (L.) Karst) is correct but the name larch (Larix sibirica) should be corrected: Siberian larch (Larix sibirica Ledeb.).
This also applies to the title and I propose to supplement it with the word Siberian. (Line 2)
In order for the name Siberian larch to be unambiguous and not to be confused with the Dahurian larch (Larix gmelinii (Rupr.) Kuzen) which is also called Siberian larch, I suggest supplementing the keywords with the Latin names of the tested species of wood. (Line 28)  
Subsequent corrections in lines: 80, 242, Table 3, 376, 405, 422, 440, 444, and 454  

References
Lines 473 and 474
Bibliographic information is incomplete and should be completed

Line 524
is:
350, E Durability
and it should be:
EN 350 Durability 

Yours sincerely
Reviewer

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Dear authors. 

Thank you for corrections in the text. 

My final comments address the following points: 

1) duration of exposure: "51" weeks is stated in line 215, on the other hand in various places "months" (pay attention to the correct data in lines 228, 402, 408, 445, 456, 467)

2) color parameter symbols used: according to the ISO 7727-3 standard, use L* (instead of L in lines 397, 422, 426) and also add "*" in the equation (line 212)

3) please detail explain "reference color" (line 297)... Did it mean the color before the exposure? The same comments apply to "target color".

4) please correct the reference to figures 7 and 8 (lines 416, 457)

5) please change "QUAT" to "quaternary ammonium compounds" (line 477, 482, table 1)

6) in figures 4,5 is a typo in the word "cpulor" 

7) please fill in additional data for ref 26

Yours sincerely

Reviewer

Author Response

Dear reviewer,

Thank you for your additional comments. We provide answers bellow and correction in to the manuscript.

Regards,

"Dear authors. 

Thank you for corrections in the text. 

My final comments address the following points: "

• duration of exposure: "51" weeks is stated in line 215, on the other hand in various places "months" (pay attention to the correct data in lines 228, 402, 408, 445, 456, 467)

Response: Thank you for your comment. Outdoor exposure began on April 1, 2019, and the last outdoor measurements were taken in July 2022 after 172 weeks. We have corrected the data throughout the document, including Figures 2-6. In the graphs, we now use a logarithmic scale for the x-axis so that the difference between treatments is clearer.

• color parameter symbols used: according to the ISO 7727-3 standard, use L* (instead of L in lines 397, 422, 426) and also add "*" in the equation (line 212)

Response: Corrected L change to L* on throughout the document.

• please detail explain "reference color" (line 297)... Did it mean the color before the exposure? The same comments apply to "target color".

 Response: Explanation added:

reference colour – colour before outdoor exposure

target colour - current colour on the day of measurement

• please correct the reference to figures 7 and 8 (lines 416, 457)

 Response: The references to figures 7 and 8 corrected

 please change "QUAT" to "quaternary ammonium compounds" (line 477, 482, table 1)

Response: Corrected in the text. In table 1 we add a note *QUAT - quaternary ammonium compounds, because in Table 1 is no space for long description

• in figures 4,5 is a typo in the word "cpulor" 

Response: Corrected

• please fill in additional data for ref 26

Response: Additional data added to reference 26