Enhanced Properties of Cryptomeria japonica (Thunb ex L.f.) D.Don from the Azores Through Heat-Treatment†
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsDear authors, please find the attached document.
Comments for author File: 
Comments.pdf
Author Response
The submitted paper „Enhanced Properties of Cryptomeria japonica from the Azores through Heat-treatment“ discuss and investigates the chemical, physical, mechanical and biological properties of thermally treated wood at 212 °C for 2 hours according to Thermo D class protocol.
The article meets the requirements of the journal in terms of both thematic and content. The research is systematic, the measured values of the investigated parameters are beneficial for the given research area, and the linguistic quality of the work is very good. However, before publication, it is necessary to correct some inaccuracies and expand or explain certain parts.
Dear authors, I present my suggestions in the following points:
- Cryptomeria japonica - the Latin name of the tree species should be written in italics in the title and throughout the text.
R: Done as suggested.
- Abstract: There is mention that „ Heat-treated wood demonstrated reduced water absorption and increased density, enhancing its suitability for applications requiring dimensional stability.“ I disagree with the claim that the density increases, because it is generally known that the density of thermally treated wood usually decreases by 5 - 15% depending on the treatment method and temperature, as water evaporates, volatile products are lost, hemicelluloses are degraded, etc. Please study the relevant literature and correct it.
R: Indeed we agree with the reviewer. This was corrected throughout the text.
- Keywords: Remove keywords (Cryptomeria japonica, Heat-treatment) that are already in the title and use a wider range of words to make your work more searchable. E.g. Thermal modification insted of Heat-treatment etc.
R: Done as suggested.
- Introduction: This part should also introduce the main objectives of the research, the purpose of the work, and its significance or use. Please add and complete.
R: Done as suggested
- Materials and Methods: The wood must be more specified in the material section. From how many trees were the samples taken? At what height of the tree? How long after felling was the wood modified and how were the samples dried, or at what moisture content of the material was the modification carried out? All this can have an impact on the monitored properties. Please describe the Thermo D modification method a little more in the methodology section.
R: All the available information about the wood was included and the Thermo D Modification has been described.
- Materials and Methods – Physical and Mechanical Properties - Density: It is stated that the density of the samples was determined. However, I still lack these results... Please complete and monitor whether the density increases or decreases (see note to the abstract).
R: This part has been removed.
- Materials and Methods – Physical and Mechanical Properties – Dimensional stability: 3 cycles are mentioned. Please specify whether it was a soaking in water, how long each cycle lasted, how long the drying took, etc. Describe the method in a way that it can be repeated.
R: Done as suggested.
- Materials and Methods – Physical and Mechanical Properties – Surface properties: Were the samples conditioned before measuring color? What was their moisture content?
R: The information was added has suggested
- Results and Discussion: Please use throughout the text more accurate term „ethanol soluble extractives“ instead of „etanol extractives“, „water soluble extractives“ instead of „water extractives“ and „dichloromethane soluble extractives“ instead of „dichloromethane extractives“.
R: Done as suggested
- Table 1: It is not possible to add up the contents of individual extracts in different solvents. Some of the solvents may extract the same substances. Delete the last column "Total". The issue of wood extraction can be found, for example, here: (Jurczyková, T., Šárovec, O., Kačík, F., Hájková, K., Jurczyk, T., & Hrčka, R. (2023). Chromophores’ Contribution to Color Changes of Thermally Modified Tropical Wood Species. Polymers, 15(19), 4000.): „Some of the most volatile compounds produced during the thermal modification of wood are released, e.g., fats, waxes, furfural, and hydroxymethylfurfural [63], and on the contrary, new extractive substances are created by the degradation of the main componente of wood, e.g., dehydration and degradation products of polysaccharides and phenolic compounds like catechol, vanillin, vanillic acid, 3-vanillyl propanol, and coniferyl aldehyde, probably resulting from lignin or phenolic extractives [64]. These remaining substances in the wood can be extracted by several solvents. Polar solvents penetrate well into the cell wall, due to which the cell wall partially swells. Organic salts, oligosaccharides, and carbohydrates can be specifically extracted from wood by water (hot or cold). Ethanol removes the tannins, dyes, or glucosides. Acetone extracts mainly the fatty and resinous acids and sterols. Non-polar solvents (e.g., benzene, petroleum ether, ether, and toluene) extract the fats, fatty acids, and their esters, resins and resin acids, waxes, and sterols from wood. The advantage of using an ethanol–toluene mixture is its non-carcinogenicity compared to benzene. Using this mixture, it is possible to extract well from the wood most phenolic substances (lignin fraction, sterol, tannin, and plobaphen), some organic acids (resin acid, amino acid, vanillic acid, and syringic acid), and other substances such as pigments and syringaldehyde [65,66].”
R: In this case it was a sequential extraction in the same sample, starting by dichloromethane, ethanol and finally water. Therefore, if a compound was already removed by ethanol cannot be removed again by water and the Total does represent the total extractives. The discussion was improved with the suggested article
- Chemical composition: You present that “A slight reduction in dichloromethane extractives and no change in water extractives were also observed. Nevertheless, it is expected that the composition of heat-treated wood extractives differs from untreated wood.“ Can you explain or justify your findings a little bit more?
R: This part has been clarified.
- Line 252: I recommend adding "lignin increases relatively" instead of "lignin increases".
R: Done as suggested
- Lines 256 – 258: inaccurate statement: „…which can be due to the equilibrium between some degradation of amorphous regions and the higher degradation of hemicelluloses.“ I recommend deleting this part and replacing it. Alpha-cellulose was determined to be predominantly crystalline and does not degrade during thermal modification. On the contrary, amorphous parts of cellulose and hemicellulose degrade. Therefore, there may be a slight apparent increase in this alpha-cellulose. (Please see for example this research: Kačík, F., Kubovský, I., Bouček, J., Hrčka, R., Gaff, M., & Kačíková, D. (2022). C olor and chemical changes of black locust wood during heat treatment. Forests, 14(1), 73.)
R: Done as suggested using the provided reference.
- Figure 2: Edit the x-axis label to English (cycles instead of ciclos); The x-axis range is sufficient from 1 to 3 and 0.5 and 3.5 do not make sense, please delete; figure caption write Cryptomeria wood - with a capital C.
R: Done as suggested
- Line 308: „in“ Table 2 instead of „on“ Table 2.
R: Done as suggested
- Table 2: In my opinion, values rounded to 2 decimal places are sufficient; Is the standard deviation 0.0768 correct? (the others are much higher)
R: Done as suggested. Yes the standard deviation 0.0768 is correct.
- Line 348: please write Cryptomeria wood - with a capital C.
R: Done
- Please discuss and explain more about the changes of mechanical properties. Use multiple sources. e.g.:
Herrera-Builes, J.F.; Sepúlveda-Villarroel, V.; Osorio, J.A.; Salvo-Sepúlveda, L.; Ananías, R.A. Effect of thermal modification treatment on some physical and mechanical properties of Pinus oocarpa wood. Forests 2021, 12, 249.
Kocaefe, D.; Poncsak, S.; Boluk, Y. Effect of thermal treatment on the chemical composition and mechanical properties of birch and aspen. BioResources 2008, 3, 517–537.
Torniainen, P.; Popescu, C.-M.; Jones, D.; Scharf, A.; Sandberg, D. Correlation of Studies between Colour, Structure and Mechanical Properties of Commercially Produced ThermoWood® Treated Norway Spruce and Scots Pine. Forests 2021, 12, 1165.
Etc.
R: This part was revised including this and additional references to the discussion.
- For comparison with other research, I recommend calculating and reporting the total color difference ΔE. Then, using this parameter, compare your results with the thermal modification of other wood species for a broader discussion.
R: Done as suggested.
- Line 387: „…it does not significantly reduce the wood's durability against termites.“ 1. Remove the word „significantly“ unless it is statistically supported. 2. Can you support this claim with the results of some other studies that looked at the resistance of thermowood to termites? Please provide sources.
R: Done as suggested.
- Table 5: Heat-treated wood is reported to have a higher moisture content than untreated samples. How is this possible? Even on line 442 in the conclusion it is stated that "heat treatment improves dimensional stability and reduces water absorption..." This needs to be clarified.
R: This column was removed to avoid confusion; this is not actually the moisture content of wood is and average of the moisture in each colony.
22. Conclusions: Line 405: please add „…degradation of amorphous fractions of cellulose…“
R: Done as suggested
Reviewer 2 Report
Comments and Suggestions for Authors1. The authors have provided the temperature and duration for thermal modification of wood, and it should be added whether the duration refers to the heating time after the core layer of wood reaches the target temperature. At the same time, the thickness of the wood and other dimensions need to be explained, the atmosphere environment also need to be added, such as the use of vacuum, nitrogen, air, or saturated water vapor and so on.
2, The chemical composition of the part of the test is too large, it is recommended that appropriate reduction.
3, Wood density, dimensional stability and water absorption test, it is recommended to add the appropriate standards and other bases.
4. Lines 353-362, changes in mechanical properties of wood, need to provide analysis and discussion of mechanisms, such as changes in chemical components, changes in moisture content, changes in wood cellulose crystallinity, etc., with specific recommendations to https://doi.org/10.1016/j.indcrop.2023.116612, https://doi .org/10.1007/s10086-006-0841-0, https://doi.org/10.1016/j.conbuildmat.2009. 08.003.
5. In order to understand the research results more intuitively, it is recommended to supplement the physical drawings of the color change of wood before and after the high temperature modification, as well as the pictures of the damage of wood specimens in the bending test.
Author Response
- The authors have provided the temperature and duration for thermal modification of wood, and it should be added whether the duration refers to the heating time after the core layer of wood reaches the target temperature. At the same time, the thickness of the wood and other dimensions need to be explained, the atmosphere environment also need to be added, such as the use of vacuum, nitrogen, air, or saturated water vapor and so on.
R: A better explanation of the Thermowood process was added in the material and methods section and the dimension of the samples was also added.
2, The chemical composition of the part of the test is too large, it is recommended that appropriate reduction.
R: Done according to the suggested
3, Wood density, dimensional stability and water absorption test, it is recommended to add the appropriate standards and other bases.
R: The used standards were added.
- Lines 353-362, changes in mechanical properties of wood, need to provide analysis and discussion of mechanisms, such as changes in chemical components, changes in moisture content, changes in wood cellulose crystallinity, etc., with specific recommendations to https://doi.org/10.1016/j.indcrop.2023.116612, https://doi .org/10.1007/s10086-006-0841-0, https://doi.org/10.1016/j.conbuildmat.2009. 08.003 .
R: The discussion was revised accordingly and the suggested articles were included with the exception of the third one that must have a different Doi since this one was not found.
- In order to understand the research results more intuitively, it is recommended to supplement the physical drawings of the color change of wood before and after the high temperature modification, as well as the pictures of the damage of wood specimens in the bending test.
R: A picture of the damage of bending test was added, where the colour changes can be also seen.
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsDear authors, thank you for your additions and corrections, now I can fully agree with publishing.
Nevertheless, please check once again all the Latin names of the tree species you are studying (Cryptomeria japonica), that it is written in italics. (I.e. these lines require correction: 2, 396, 400, 452, 457, 459, 464, 467, 469, 472, 484, 492, 508, 528.) = MINOR REVISIONS.
Thank you and good luck with your further research!
Author Response
Dear Reviewer,
Thank you for your comments that certainly enriched the paper. All the species have now the Latin name. The confusion was that in Portuguese the common name for Japanese cedar is Criptomeria.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe author has responded to every review comment, and the quality of the article has significantly improved. It is recommended for publication.
Author Response
Dear Reviewer,
Thank you for your comments that certainly enriched the paper.
