Quality Control of Thermally Modified Timber Using Dynamic Vapor Sorption (DVS) Analysis

Round 1

Reviewer 1 Report

P1, Is it possible to strictly say that correlation works for all processes as correlations in table 3 does not specify whether it is the Silvapro process or what process the data is taken from? 

L36 processes?

P2 L 56-57 I miss superheated steam is one of the most common such as thermowood 

L 75 Following ref. should be included  "Industrial Validation of the Relationship between Color Parameters in Thermally Modified Spruce and Pine, Petteri Torniainen, Diego Elustondo, Ola Dagbro, Vol 11, No 1 (2016) Bioresources"

L 85 This is of interest since it is reported that some reduced sorption is lost after soaking of TMT in water. Could that be commented?

P3 L97 How were these samples taken from the log, were they dried before TMT to what MC?

L102 "All specimens were from the same material" sounds strange...  

L105-106 Mininmize is it correct word? I think decrease could be more appropriate but has this method been shown to decrease oxidation or is it just a suggestion? It could also be that evaporation is slowed down and that degradation and/or condensation product formation is increased. In L1175 condensation is proposed to explain the results.

L115 Willems (2009) what kind of reference is that? Is this performed in small or big autoclave?

L123 Envelope density, what density is it? What was the size of sand grain, do they penetrate into wood?

L138 The whole board was scanned? both dimensions o2 12x12x30mm3?

L161 How many scans per min is better to say.

L168 Material from closed process was used as comparison. The reason for using such kind of material as reference should be motivated. Furthermore, Is this really a reference material I think it presented more like another type of TMT. Explain more!

L179 The sentence is written like pH was meassured but where could I find the data on pH of the TMT specimens in the paper?

L188-189 Klason lignin (it is not native lignin!) should be used instead of lignin as it was used to compare colour differences upon thermal treatments. 

L222 Was crystallinity of wood measured?

L255 which subchapters?

L257 But lightness in this study increases with treatment temperature. See table 1 ! maybe correlation to mass loss but that was not written here.

L259 What about the influence of TM treatment method. Are the calculations based on all these methods together?

L261 should be -0.88 and -0.90 

L262 it was not shown that L* could be used for weathered wood, this is only a speculation.

L264 How do we know that the natural variability on wood density was the the most influential?

L275 To study the applicability of the developed method,....

L277 the reference 15 is hard to find and ref. 42 is only about open system TMT

L275 Influence of planing depth was not investigated or discussed so this conclusion is little bit too much.

So what about the influence of foil was it better or not I think that should be commented. What about the silvapro process and such correlations should also be answered.

Author Response

Response to reviewer 1

Dear editors. Thank you very much for your mail regarding the manuscript. We appreciate the efforts of the reviewers to improve the manuscript. We have tried to consider the comments fully. Response to the respective comments is resolved below and indicated in the text. We have tried our best to address all of the comments. In case of any issues or misunderstandings, do not hesitate to contact me.

Comment: P1, Is it possible to strictly say that correlation works for all processes as correlations in table 3 does not specify whether it is the Silvapro process or what process the data is taken from?

Response: Thank you for your respective comment. The correlation works for several modification processes, but extrapolation to all of the thermal modification processes would be too ambitious without scientific proof.

Comment: L36 processes?

Response: Comment was fully considered. The text was changed as suggested 

Comment: P2 L 56-57 I miss superheated steam is one of the most common such as thermowood

Response: Comment was fully considered. The text was changed as suggested 

Comment: L 75 Following ref. should be included  "Industrial Validation of the Relationship between Color Parameters in Thermally Modified Spruce and Pine, Petteri Torniainen, Diego Elustondo, Ola Dagbro, Vol 11, No 1 (2016) Bioresources"

Response: Comment was fully considered. Reference was added. Change in the text is not highlighted.

Comment: L 85 This is of interest since it is reported that some reduced sorption is lost after soaking of TMT in water. Could that be commented?

Response: Constant sorption properties were proved at wood exposed in use classes 2 and 3.1. The text was changed to clarify this statement.

Comment: P3 L97 How were these samples taken from the log, were they dried before TMT to what MC?

Response: Comment was fully considered. Additional text was provided. Drying and samples selection was provided.

Comment: L102 "All specimens were from the same material" sounds strange... 

Response: Comment was fully considered. The text was changed.

Comment: L105-106 Mininmize is it correct word? I think decrease could be more appropriate but has this method been shown to decrease oxidation or is it just a suggestion? It could also be that evaporation is slowed down and that degradation and/or condensation product formation is increased. In L1175 condensation is proposed to explain the results.

Response: Comment was fully considered. Term decrease was used.  As the characteristics of the modification are described further on, we did not want to mix methods with the results. 

Comment: L115 Willems (2009) what kind of reference is that? Is this performed in small or big autoclave?

Response:  Reference formatting was changed. Experimental details were provided. The modification was performed on a laboratory scale.

Comment: L123 Envelope density, what density is it? What was the size of sand grain, do they penetrate into wood?

Response: Reference for envelope density was provided. This term is frequently used in material science. They do not penetrate the wood. Text was changed to clarify this issue.

Comment: L138 The whole board was scanned? both dimensions o2 12x12x30mm3?

Response: Samples were scanned before cutting to smaller sizes. Text was updated to clarify this issue.

Comment: L161 How many scans per min is better to say.

Response: Comment was fully considered. Text was updated.

Comment: L168 Material from closed process was used as comparison. The reason for using such kind of material as reference should be motivated. Furthermore, Is this really a reference material I think it presented more like another type of TMT. Explain more!

Response: Comment was fully considered. The text was changed. Term reference was not appropriate and was replaced.

Comment: L179 The sentence is written like pH was meassured but where could I find the data on pH of the TMT specimens in the paper?

Response: There were additional methods applied on the respective materials. All of them are not reported in the respective manuscript, as the manuscript would be too confused and confusing to follow. In the cited reference, there is a master thesis, where pH data can be resolved. Additional text was provided as well. 

Comment: L188-189 Klason lignin (it is not native lignin!) should be used instead of lignin as it was used to compare colour differences upon thermal treatments.

Response:  Comment was fully considered. Term was changed

Comment: L222 Was crystallinity of wood measured?

Response: Cystalinity was not measured, unfortunately.

Comment: L255 which subchapters?

Response: Text was corrected.

Comment: L257 But lightness in this study increases with treatment temperature. See table 1 ! maybe correlation to mass loss but that was not written here.

Response: This part of the text was corrected to resolve this misunderstanding.

Comment: L259 What about the influence of TM treatment method. Are the calculations based on all these methods together?

Response:  For correlations calculations, all date from various treatments were merged.

Comment: L261 should be -0.88 and -0.90

Response: Comment was fully considered

Comment: L262 it was not shown that L* could be used for weathered wood, this is only a speculation.

Response:  Method was not tested on wethered wood. Text was updated to clarify this presumption.

Comment: L264 How do we know that the natural variability on wood density was the the most influential?

Response: Text was updated. Additional comment was provided to discuss this question.

Comment: L275 To study the applicability of the developed method,....

Response: Comment was fully considered.

Comment: L277 the reference 15 is hard to find and ref. 42 is only about open system TMT

Response: I do agree that some of the references are hard to find. However, if urgent potential readers can always contact lead or first author for authors copy. Besides, we have provided additional reference, based on the reviewer comment.

Comment: L275 Influence of planing depth was not investigated or discussed so this conclusion is little bit too much.

Response: Conclusion was changed as suggested.

Comment: So what about the influence of foil was it better or not I think that should be commented. What about the silvapro process and such correlations should also be answered.

Response: Comment was fully considered. Additional conclusions were provided.

Reviewer 2 Report

Please find all my comments in the pdf.

Comments for author File: Comments.pdf

Author Response

Response to reviewer 2

Dear editors. Thank you very much for your mail regarding the manuscript. We appreciate the efforts of the reviewers to improve the manuscript. We have tried to consider the comments fully. Response to the respective comments is resolved below and indicated in the text. We have tried our best to address all of the comments. In case of any issues or misunderstandings, do not hesitate to contact me.

Comment: Authors should consider that quality of treated (TMT) wood is a ratehr complex issue. Especially deformations occured during the treatment, crack (micro, macro) are sever factors, which if not controlled adequately the quality is tending fire wood, however massloss would indicate good durability. Might author change the title to (e.g.) Control of modification's degree....., instead of quality control. At least a paragraph must be incorporated what quality should mean in wood utilisation.

Response: We appreciate the efforts of the reviewer. We agree that the modification is an extremely complex field. This can be evident from the number of publications addressing this question. We tested the meaning of the term Control of modification's degree. However, we believe that the respective title better reflects the manuscript content.

Comment: Authors should explain the indication of 2 different specimen sizes. Why not the same size? Probably RxTxL?

Response: There were different experiments performed. All of them are not reported. This part was revised to make it more clear.

Comment: Authors should consider the effect of the metal foil, might serving as a barrier, thus keeping the degradation products within the wood. If this effect was present authors should write about this.

Response: We appreciate the respective comment. We agree that foil likely affects the modification process. This part is discussed in the results section, as we do not want to mix results with methods.

Comment: Authors choose different temperatures for beech and spruce. Why?

Response: In general hardwoods are modified at lower temperatures than softwoods. This can be evident from thermowood process as well. The additional sentence in the methods was provided to clarify this issue.

Comment; 160°C and 170°C for spruce and beech? Why 2 different peak-temperatures given?

Response: The respective modification was performed on spruce wood only. The text was modified to avoid possible confusions.

Comment: How the surfaces were prepared for the colour measurements? Any sanding applied? Especielly when samples wrapped, condensates can accumulate on the surface.

Response:  Comment was considered. To avoid confusions, we have updated the methodology. The surface of the samples was not sanded or planed before the measurements. There were no condensates determined on the surface, which might affect the colour. Samples were scanned before cutting to smaller sizes.

Comment: If I understood correctly, the colour was not mesured by colorimeter but was digitalized (scanned) firts. How accurate this measurement methos could be? Any own tests conducted? Are there any literatures evaluated thsi?

Response: We are running this type of tests regularly. Measurements have to be performed carefully, and scanning parameters have to be controlled. We have performed a comparison and validate the methodology. To clarify this issue, additional methodological reference was provided.

Comment: What is the physical/chemical background of this uniformity in colour? Can the wrapping serve as a promising technique at industrial scale to acheive uniform colour?

Response: One of the possible reasons could be fact, that Al foil transfers and distributes heat uniformly through the samples.

Comment:  In Tab 1. teher are data presented at higher pressure values (1, 3, 8 bar). I could not find info to this in Matreial and methodes.

Response: Respective data are provided in the material and methods.

Round 2

Reviewer 1 Report

My comments has been considered by the authors and the manuscript has been adjusted in an appropriate way. So I suggest the manuscript is in the condition of being subject for publishing.