Research on the Dyeing Properties of Chinese Fir Using Ultrasonic-Assisted Mulberry Pigment Dyeing
Round 1
Reviewer 1 Report
The manuscript deals with a research study of optimization of a dyeing process of Chinese Fir by using an ultrasonic device. The study is interesting for different stakeholder, but the current presentation is not suitable for the Journal Forests.
The results are not inline with the material and methods used (e.g. dye concentrations, temperature, …). Therefore, the reader cannot follow the results and understand the differences between the used methods and the results. The description of the methods (e.g. single factor test and orthogonal test factors) are not clear.
Further comments:
Line 40: “… often exhibits defects such as poor dimensional stability, ...” Are these poor material properties really defects? The topic here is the expectations of the material properties and also the application of such materials. Not every material can be used for every application (e.g. outdoor). Therefore, this sentence should be changed.
Line 162: “… with NaOH were immersed …” Which concentrations had the NaOH? Within the conclusion section the authors mentioned the degradation of cellulose, hemicellulose and lignin due to the ultrasonic process. However, which influence did the NaOH treatment has?
Table 1 and Table 2 present different parameters of the study (e.g. Table 1: Temperature: 30, 50, 70, and 90 °C as well as Table 2: Temperature 50, 65, and 80 °C). Also, within the subsection 2.2.2. Optimization experiment of ultrasound-assisted mulberry dyeing process on Chinese fir wood was given the temperature 50, 70 and 90 °C. Why is there a difference?
Determination of colour differences: Please mention the used standard illuminant and observer for this method;
Fourier transform infrared analysis: Which data pre-treatment (e.g. basisline correction, normalizations) of the FT-IR spectra were used?
Which unit (NBS) did you use for the results of the color difference? Normally, the values of the CIELab colour space have not unit.
Please mention the missing data for the Figures 3, 4, 5, and 6 (e.g. power, dye concentration, time, temperature). The reader cannot understand if you do not write the missing data. For example – Figure 3: The results were given depending on the power (W) of the ultrasonic impregnation process. However, which temperature, dye concentration and processing time were used?
Figure 5: Which unit was used for the time? Is % the correct unit?
Figure 7: What did the authors mean with “sequence”? Is “sequences” equal with “serial numbers”?
Section 3.9 and Figure 10: Please add also the IR-Spectrum of the mulberry pigment extract. It would be very helpful for the description of the results. I guess that also mulberry pigment extract has unsaturated functional groups (e.g. phenylpropanoid-based) and has probably an absorbance around 1600 - 1500 cm-1.
Author Response
Dear reviewer,
Thank you very much for your comments and professional advice. These opinions help to improve academic rigor of our article. Based on your suggestion and request, we have made corrected modifications-on the revised manuscript. We hope that our work can be improved again. Furthermore, we would like to show the details as follows:
Line 40: “… often exhibits defects such as poor dimensional stability, ...” Are these poor material properties really defects? The topic here is the expectations of the material properties and also the application of such materials. Not every material can be used for every application (e.g. outdoor). Therefore, this sentence should be changed.
Reply：
We’ve changed [However, wood, especially fast-growing wood, often exhibits defects such as poor dimensional stability, low physical and mechanical strength, and uneven coloration] to [However, wood, especially fast-growing wood, often exhibits the problem of uneven timber color and single timber color] (line 41-42)
Line 162: “… with NaOH were immersed …” Which concentrations had the NaOH? Within the conclusion section the authors mentioned the degradation of cellulose, hemicellulose and lignin due to the ultrasonic process. However, which influence did the NaOH treatment has?
Reply：
The use of sodium hydroxide (NaOH) immersion for pretreating Chinese fir was described in Section 2.1.1, with a NaOH concentration of 1.2%. According to our previous research and literature review, NaOH treatment partially degrades cellulose and hemicellulose in the wood. The NaOH pretreatment enhances the permeability of the wood, facilitating the diffusion and penetration of dyes during the wood dyeing process.
Table 1 and Table 2 present different parameters of the study (e.g. Table 1: Temperature: 30, 50, 70, and 90 °C as well as Table 2: Temperature 50, 65, and 80 °C). Also, within the subsection 2.2.2. Optimization experiment of ultrasound-assisted mulberry dyeing process on Chinese fir wood was given the temperature 50, 70 and 90 °C. Why is there a difference?
Reply：
We apologize for our error，due to inadvertent writing errors in the table, the temperature settings in the orthogonal experiment section should follow the temperatures listed in the text, which are 50, 70, and 90°C. The temperatures for the orthogonal experiment were determined based on the single-factor experiments.
Determination of colour differences: Please mention the used standard illuminant and observer for this method;
Reply：
The light source of the spectrophotometer is a tungsten filament lamp. The spectrophotometer can be used to measure the color parameters of the wood surface and display the measured L, a, b, and other color parameters on the instrument. The experimenters measured the color parameters of the wood before and after dyeing using the spectrophotometer, and then calculated the color difference of the wood after dyeing.
Fourier transform infrared analysis: Which data pre-treatment (e.g. basis line correction, normalizations) of the FT-IR spectra were used?
Reply：
In infrared analysis, we performed baseline correction, smoothing and normalization of the spectra.
Which unit (NBS) did you use for the results of the color difference? Normally, the values of the CIELab colour space have not unit.
Reply：
Thank you for your reminder. We have reconfirmed that color difference indeed has no unit, and it has been removed from the manuscript.
Please mention the missing data for the Figures 3, 4, 5, and 6 (e.g. power, dye concentration, time, temperature). The reader cannot understand if you do not write the missing data. For example – Figure 3: The results were given depending on the power (W) of the ultrasonic impregnation process. However, which temperature, dye concentration and processing time were used?
Reply：
Annotations have been added below Figure 3, Figure 4, Figure 5, and Figure 6, and corresponding explanations have been provided in the main text regarding temperature, dye concentration, and treatment time.（line296, line319, line322, line336, line339, line361, line364, line 384）
Figure 5: Which unit was used for the time? Is % the correct unit?
Reply：
Thank you for your reminder. Due to an oversight, the units were written incorrectly. The units have now been changed to hours (h).(line359)
Figure 7: What did the authors mean with “sequence”? Is “sequences” equal with “serial numbers”?
Reply：
the sequence represent the serial numbers of the nine experimental groups in the orthogonal experiment, where each group represents different experimental conditions. Both expressions convey the same meaning, and I have now made the necessary modifications to ensure consistency. (Line 395)
Section 3.9 and Figure 10: Please add also the IR-Spectrum of the mulberry pigment extract. It would be very helpful for the description of the results. I guess that also mulberry pigment extract has unsaturated functional groups (e.g. phenylpropanoid-based) and has probably an absorbance around 1600 - 1500 cm-1.
Reply：
The infrared analysis diagram of mulberry pigment has been added and analyzed in the corresponding part of the paper. Please see lines 509-512, line 516-522.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Title: Research on the Dyeing Properties of Chinese Fir Using Ultrasonic-Assisted Mulberry Pigment Dyeing.
Overall Comments:
The paper discusses the dyeing of softwood using ultrasonication in 80% ethanol as a solvent. The presentation of the paper is inadequate. The main weakness of this paper lies in its lack of detailed scientific explanation and insufficient information in the experimental section. Consequently, the current manuscript is not suitable for publication. The reviewer recommends a "major revision."
Comments on the Title, Abstract, and References:
The title should incorporate the name of the natural dye used.
The abstract is informative and effectively represents the study. However, the authors should include a statement highlighting the novelty of their work.
The chosen keywords are appropriate.
References need to be updated, and irrelevant references should be removed.
Comments on the Introduction:
Lines 45-49: Please include the advantages and disadvantages of the dyeing process.
Lines 74-75: "Furthermore, ultrasound-assisted dyeing significantly reduces dyeing time, conserves dye volume, and minimizes energy consumption." In what context does it reduce energy consumption?
Lines 76-78: The intended meaning is unclear. Why is further research needed for dyeing wood using an ultrasonic approach?
Lines 95-111: This section requires revision as the information provided is irrelevant to this study.
Is this study the first to report the use of mulberry natural pigment?
The objective of this study needs clarification. Please refine it in the introduction.
Comments on Materials and Methods:
Line 126: Change "Water content"
Why is distilled water necessary for this experiment?
Why were the samples treated with NaOH and then dried before dyeing? Please specify the air-drying time and temperature. How was the moisture content percentage measured? Is it assumed that all samples have a 12% moisture content? How many samples were used for these experiments, and how many times were the experiments repeated? Were there any cracks or size deformations due to the NaOH treatment?
Lines 140-141: What filter paper separated the insoluble matter?
Did the filter paper absorb the dye color?
Line 160: What was the temperature of the ultrasonic bath?
Figure 1: The caption is missing.
Line 179: "Each experiment was repeated six times." Please verify this statement.
Please indicate the volume of the ethanolic pigment solutions used for each experiment.
Given that an 80% ethanolic dye solution was used for wood dyeing, how did the authors maintain the dye solution concentration for 7 hours at a temperature of 90 degrees Celsius, considering ethanol's evaporation?
The image of wood samples in a beaker shows them floating on the solvent's surface. Therefore, is it questionable whether the dye color disperses uniformly on the wood surface?
Determination of Dye Uptake:
This test may not have been performed correctly due to difficulty maintaining dye concentration in the solvent. Lines 340-341 state, "As the dye concentration increases, the number of dye molecules per unit volume increases, leading to dye molecule aggregation and hindering diffusion into the wood."
Comments on Results and Discussion:
Overall, this section lacks scientific rigor and explanations. Careful explanations are needed for all characterization results (FTIR, XRD, SEM).
Line 451: "Ultrasound's cavitation and thermal effects cause rapid vaporization of moisture in the wood." The authors should provide a detailed explanation.
Is the sample referred to as "undyed" the NaOH-treated sample or an untreated one?
Comments on Conclusion:
What is the conclusion of this study and its limitation and utility?
Author Response
Dear reviewer,
Thank you very much for your comments and professional advice. These opinions help to improve academic rigor of our article. Based on your suggestion and request, we have made corrected modifications-on the revised manuscript. We hope that our work can be improved again. Furthermore, we would like to show the details as follows:
Comments on the Title, Abstract, and References:
The title should incorporate the name of the natural dye used.
Reply：The title already contains the name of the natural dye, and the natural color dye is “Mulberry Dye”.
The abstract is informative and effectively represents the study. However, the authors should include a statement highlighting the novelty of their work.
Reply：
We have revised the text to address your concerns and hope that it is now clearer. Please see lines 26-29.
The chosen keywords are appropriate.
Reply：
Keywords have been modified in the keyword section, please see lines 30-31.
(We’ve changed [ultrasonic-assisted; Mulberry pigment; Chinese fir; Natural pigment; Color fastness; Fuzzy com-prehensive evaluation method] to [However, wood, especially fast-growing wood, often exhibits the problem of uneven timber color and single timber color] )
References need to be updated, and irrelevant references should be removed
Reply：
Some irrelevant literature has been deleted
Comments on the Introduction:
Lines 45-49: Please include the advantages and disadvantages of the dyeing process.
Reply：
The advantage of wood staining is that it achieves deep coloration, and the color of the wood is less likely to fade due to surface abrasion. However, the disadvantage of wood staining lies in the use of multiple reagents and additives in the staining process, difficult treatment of waste liquid, and lower color fastness after wood staining. Modifications have been made in the manuscript, please see lines 50-53.
Lines 74-75: "Furthermore, ultrasound-assisted dyeing significantly reduces dyeing time, conserves dye volume, and minimizes energy consumption." In what context does it reduce energy consumption?
Reply：
Under the assistance of ultrasound, the required staining temperature and time to achieve the same staining effect are reduced.
Lines 76-78: The intended meaning is unclear. Why is further research needed for dyeing wood using an ultrasonic approach?
Reply：
We have revised the text to address your concerns and hope that it is now clearer. Please see lines 80-84.
Lines 95-111: This section requires revision as the information provided is irrelevant to this study.
Reply：
We have revised the text to address your concerns and hope that it is now clearer. Please see lines 100-109.
Is this study the first to report the use of mulberry natural pigment?
Reply：
To be precise, it was probably the first application in wood dyeing
The objective of this study needs clarification. Please refine it in the introduction.
Reply：
We have revised the text to address your concerns and hope that it is now clearer. Please see lines 110-116.
Comments on Materials and Methods:
Line 126: Change "Water content"
Reply：
The “water content“ has been changed to ”moisture content“.
Why is distilled water necessary for this experiment?
Reply：
After NaOH pretreatment and wood staining, it is necessary to rinse the residual NaOH solution and dye liquor from the stained wood using distilled water.
Why were the samples treated with NaOH and then dried before dyeing? Please specify the air-drying time and temperature. How was the moisture content percentage measured? Is it assumed that all samples have a 12% moisture content? How many samples were used for these experiments, and how many times were the experiments repeated? Were there any cracks or size deformations due to the NaOH treatment?
Reply：
NaOH pretreatment is primarily aimed at enhancing wood permeability, which facilitates better penetration and diffusion of mulberry dye into the wood during subsequent coloring processes. In this study, the moisture content of the wood was measured using the weighing method. The calculation formula for wood moisture content is as follows:
Where W is the moisture content, m0 is the absolute dry weight of wood, and m1 is the wet weight of wood. The temperature of wood drying is 25℃, and the drying time is about 7 days. It is not assumed that the moisture content of all samples is 12%, but by drying, the moisture content of the wood is controlled at the same level.
NaOH pretreatment was performed on all dyed and undyed samples, and NaOH pretreatment was performed only once for each sample.
There was no crack in the wood, but there was dimensional deformation, and some specimens were slightly warped after NaOH treatment
Lines 140-141: What filter paper separated the insoluble matter?
Reply：A quantitative filter paper is used
Did the filter paper absorb the dye color?
Reply：
Yes, the filter paper is partially stained.
Line 160: What was the temperature of the ultrasonic bath?
Reply：
Different ultrasonic power settings (0, 100W, 180W, 260W, 340W) were established while keeping the staining temperature (90°C), staining time (7h), and dye concentration (15%) constant.
Figure 1: The caption is missing.
Reply：
A title has been added below Figure 1. Please see line 178.
Line 179: "Each experiment was repeated six times." Please verify this statement.
Reply：
In the "Supplementary Material" file, the “Single factor test” and "Orthogonal Experimental" worksheet section documented six sets of data for each test of each indicator.
Please indicate the volume of the ethanolic pigment solutions used for each experiment.
Reply：
The liquor ratio was 1:40, indicating a ratio of 1 part sample volume to 40 parts dye solution volume. With a sample volume of 9cm3, the volume of dye solution used for each application was 360ml. It has been described in the article, please see line171.
Given that an 80% ethanolic dye solution was used for wood dyeing, how did the authors maintain the dye solution concentration for 7 hours at a temperature of 90 degrees Celsius, considering ethanol's evaporation?
Reply：
The dye does not contain ethanol. In the preparation process of mulberry dye, ethanol is used to wash off the mulberry pigment solution. Then, the solution is concentrated using a rotary evaporator, during which the ethanol solution mostly evaporates, resulting in the enrichment of mulberry pigments. Therefore, the dye used in the subsequent dyeing process does not contain ethanol. Ethanol is only used to wash off the mulberry pigment and is not part of the dye itself.
The image of wood samples in a beaker shows them floating on the solvent's surface. Therefore, is it questionable whether the dye color disperses uniformly on the wood surface?
Reply：
When dyeing, the wood sample is completely immersed in the dye. The flowchart indicates a defect and has been modified. Line 176.
Determination of Dye Uptake:
This test may not have been performed correctly due to difficulty maintaining dye concentration in the solvent. Lines 340-341 state, "As the dye concentration increases, the number of dye molecules per unit volume increases, leading to dye molecule aggregation and hindering diffusion into the wood."
Reply：
Regarding the problem of ethanol in the dye solution, the relevant explanation has been carried out before. In addition, during the experiment, in order to prevent the evaporation of the dye water and affect the concentration of the dye, we used plastic wrap to seal the beaker mouth containing the dye water to reduce the evaporation of water and ensure the accuracy of the dye concentration as much as possible.
Comments on Results and Discussion:
Line 451: "Ultrasound's cavitation and thermal effects cause rapid vaporization of moisture in the wood." The authors should provide a detailed explanation.
Reply：
This process has been supplemented in more detail in the text, please see lines 492-497.
Is the sample referred to as "undyed" the NaOH-treated sample or an untreated one?
Reply：
The samples referred to as "undyed" are the ones that underwent NaOH treatment. In this study, all samples of Chinese fir were pretreated with NaOH (the purpose of NaOH pretreatment was to enhance wood permeability) before staining was conducted. The various indicators and characterizations in the article mainly involve a comparison between the Chinese fir before and after staining.
Comments on Conclusion:
What is the conclusion of this study and its limitation and utility?
Reply：
Conclusion：The experiments showed that ultrasound-assisted treatment improved the dye uptake and color difference of mulberry-dyed Chinese fir. Through characterization, the role of ultrasound in the wood dyeing process was analyzed: electron microscopy analysis revealed that ultrasound increased the cracks in the wood cell walls, providing more attachment sites for dye molecules; infrared analysis showed that under the influence of ultrasound, the degradation degree of the three major constituents of Chinese fir increased, with large wood molecules degrading into smaller ones, facilitating the penetration of dye molecules into the wood; XRD analysis demonstrated that ultrasound reduced the crystallinity of fir wood, further promoting the penetration of dyes into the wood. Additionally, this study obtained the optimal process for ultrasound-assisted mulberry dyeing of Chinese fir through orthogonal experiments and fuzzy comprehensive analysis.
Limitations: The staining performance needs further improvement, especially in terms of color fastness.
utility: Achieving coloring of wood with natural pigments is beneficial for reducing the use of toxic and harmful chemical dyes, providing references for the environmentally friendly and sustainable development of the wood dyeing industry.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors reworked the mansucript. Now, it is easier to read.
They used the CIELab colour space for the analysing, but in the results only the NBS units were used. How were the DE* values convert to the NBS units? Which equation was uesd? Normally, the CIELab values do not have a unit.
Author Response
Dear reviewer,
Thanks for you meaningful comments. Please find a detailed reply in the attachment.
Author Response File: Author Response.docx
Reviewer 2 Report
The authors replied to reviewer comments and improved the manuscript accordingly. The paper could be accepted for publication.
Best wishes!
Author Response
Dear reviewer,
Thank you again for your positive comments and valuable suggestions to improve the quality of our manuscript.
