Novel Adhesive Film for Glyoxal-Dehydrated Lacquerware: Composite Modification of Natural Lacquer with Soy Protein Isolate and Nano-SiO2
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe study addresses a critical challenge in the conservation of cultural heritage: the bonding failure of lacquerware treated with glyoxal dehydration. The authors developed a multi-component composite adhesive by modifying natural lacquer with Tween-20, soy protein isolate (SPI), and nano-filler. However, the revisions are required to make this manuscript suitable for publication.
- The title of the manuscript contains a minor typographical error.
- The Introduction is well-structured but requires minor revisions to strengthen the justification for Tween-20 and address international conservation ethics regarding reversibility.
- The author should present the full results of all experimental runs rather than focusing only on the optimized formulation. Providing only selective data not only leads to reader confusion but also prevents a rigorous academic analysis of how different factors and their specific levels influence the adhesive's performance. A complete data disclosure is essential for evaluating the sensitivity of each variable and confirming the scientific validity of the optimization process.
- Since this study involves four distinct factors, the experimental results should be explained and discussed by analyzing each factor individually. This approach is necessary to identify the most significant variables clearly and to understand how each specific component influences the overall properties of the adhesive.
- In materials and methods, to ensure full reproducibility, the authors should provide more details on the control of bondline thickness and the initial moisture content/surface preparation of the fir wood. Additionally, for the XPS analysis, please clarify the specific procedure used to prepare the interface samples to ensure that the detected Si-O-C bonds accurately represent the wood-lacquer interaction rather than surface contamination. Moreover, the authors should ensure that the brand names, model numbers, and manufacturers' locations for all analytical instruments are provided consistently throughout the Materials and Methods section.
- Abbreviations like HLB, SPI, and RH are listed in the appendix but should be consistently defined upon their first mention in the main text to assist readers who may not refer to the back of the paper.
- The Title and Headers: A significant spelling error occurs
Author Response
Comment 1：The title contains a minor typographical error.
Response1：:Corrected. The missing initial letter has been restored.
Revised: “Novel Adhesive Film for Glyoxal-Dehydrated Lacquerware”.
Comment 2：Strengthen the justification for Tween-20 selection.
Response2：We have expanded Section 1.2.4 to explain the physicochemical rationale for selecting Tween-20, including its high HLB value, improved wetting ability, and chemical compatibility with urushiol systems. This clarifies why Tween-20 is particularly suitable for conservation use rather than alternative surfactants.
Comment 3:：Address international conservation ethics regarding reversibility.
Response：A new paragraph has been added in the Introduction discussing compatibility and retreatability in lacquer conservation. We clarify that although complete reversibility is limited for lacquer-based systems, chemically compatible materials are traditionally preferred in lacquer restoration practice. This contextualizes the material choice within accepted conservation ethics.
Comment 4：Present the full results of all experimental runs.
Response 4：:We fully agree. A new section (Section 3.1) and Table 3 have been added presenting the complete dataset of all nine orthogonal runs (A–I), including shear strength and moisture resistance results (mean ± SD, n = 5). This ensures full transparency and allows readers to evaluate factor sensitivity and the scientific validity of the optimization process.
Comment 5：Provide more methodological details to ensure reproducibility.
Response 5：:Additional experimental details have been included:
1、 bondline thickness control (80 ± 10 μm)
2、 wood moisture content conditioning (10 ± 1%)
3、 surface preparation protocol
4、 cryo-fracture preparation for XPS interfaces
5、 full instrument brand/model/location information
These additions ensure reproducibility.
Comment 6：Define abbreviations at first mention and improve English language.
Response 6：:All abbreviations (SPI, RH, HLB) are now defined upon first appearance. The manuscript has been thoroughly proofread, and grammar, spacing, and terminology have been corrected throughout.
Reviewer 2 Report
Comments and Suggestions for AuthorsGeneral comments:
It describes a materials-science-based conservation study that creates and validates a high-performance, compatible adhesive for the restoration of ancient lacquerware, combining traditional materials with nanotechnology to achieve stronger, more stable, and visually acceptable repairs. I recommend it for this journal.
Supplement this table caption with info if these are model samples or real samples
I know in table to for mold growth there is only 2 cases: tehre is mold and tehre is no mold and results are presented in this table 2 , however in this case you must include 2 figures one showing on model samples with mold and the other one without mold. Othervise this evaluation is just to subbjective as no microbiological quantification is given. Methodological transparency is lacking in the microbiological assessment (how “mold growth” was evaluated). It has to be written more precise and has to be extended or mold assesment has to be removed completely from manuescript.
Although reversibility is discussed conceptually, no experimental tests were performed to assess removability or retreatability of the cured adhesive, which is a core conservation requirement. How do the authors respond to this?
Shift orthogonal design details and Table 1 into Methods. What to move: Full L9(3⁴) design description, level tables, and step‑by‑step mixing parameters. These are experimental details that interrupt the conceptual flow of the Introduction. Keep a short summary of the design in the Introduction (one sentence).
Specific comments:
Better to write: A novel composite adhesive for lacquer film restoration was developed by modifying natural lacquer with Tween-20, soy protein isolate (SPI), and nano-SiO₂ to overcome the bonding limitations of glyoxal-dehydrated lacquerware. [Abstract]
Better to write: The optimal formulation (70% lacquer, 10% Tween-20, 15% SPI, and 5% nano-SiO₂) achieved a shear bond strength of 3.8 ± 0.3 MPa, corresponding to a 58% increase compared with pure lacquer (2.4 ± 0.2 MPa). [Abstract]
Better to write: Residual glyoxal and its degradation products generate a weakly acidic microenvironment (pH ≈ 4–5), which accelerates interfacial degradation and significantly compromises the bonding performance of conventional lacquer-based adhesives. [1.1 Background and Significance]
Better to write: Therefore, the development of adhesives specifically tailored for glyoxal-dehydrated lacquerware is of critical importance for effective conservation. [1.1 Background and Significance]
Better to write: Soy protein isolate (SPI) has received increasing attention as a bio-based adhesive modifier owing to its excellent film-forming capability and abundance of reactive functional groups. [1.2.4 Functional Bio-Based and Nano-Modified Additives]
Better to write: An L9(3⁴) orthogonal experimental design was employed to systematically evaluate four factors at three levels: lacquer content (60%, 70%, 80%), Tween-20 (5%, 10%, 15%), SPI (5%, 10%, 15%), and nano-SiO₂ (3%, 5%, 7%). [2.2 Experimental Design]
Better to write: The optimal formulation (D: 70% lacquer, 10% Tween-20, 15% SPI, and 5% nano-SiO₂; Figure 1) was prepared at pilot scale by first mixing purified lacquer and Tween-20 at 1500 rpm for 10 min, followed by addition of SPI and nano-SiO₂ (pre-dispersed in minimal water) under ultrasonication (20 kHz, 30 min), and subsequent aging for 24 h at 25 °C to remove entrapped air, yielding a final viscosity of 1300 ± 50 mPa·s. [2.3 Adhesive Preparation]
Better to write: After 30 days of immersion in a pH 4.0 solution, formulation D retained 91 ± 3% of its initial shear strength, significantly higher than that of pure lacquer (65 ± 5%, p < 0.001). [3.2 Acid Resistance]
Better to write: Under accelerated aging conditions (50 °C/95% RH), formulation D exhibited minimal weight gain (1.0 ± 0.2%) and no visible mold growth after 30 days, whereas pure lacquer showed greater moisture uptake (3.0 ± 0.4%) accompanied by visible mold formation (p < 0.001). [3.3 Moisture Resistance and Mold Prevention]
Better to write: add reference - Under 50°C/95% RH aging, formulation D showed 1.0 ± 0.2% weight gain with no visible mold after 30 days, compared to pure lacquer (3.0% weight gain with visible mold spots) (p < 0.001). Kosel, et al. Evaluating the xerophilic potential of moulds on selected egg tempera paints on glass and wooden supports using fluorescent microscopy. Journal of Cultural Heritage [3.3 Moisture Resistance and Mold Prevention].
Better to write: XPS analysis of the wood–lacquer interface revealed substantially enhanced interfacial bonding arising from synergistic multi-component interactions. [3.5.1 Interface Chemical Bonding Enhancement]
Better to write: Nano-SiO₂ contributes to covalent interfacial bonding, as surface Si–OH groups condense with cellulose hydroxyls to form Si–O–C linkages, evidenced by XPS Si 2p peaks at 102.4 eV and C–O–Si signals at 286.5 eV. [3.5.1 Interface Chemical Bonding Enhancement]
Better to write: A Warring States period (475–221 BCE) lacquer cup excavated from Yunmeng Shuihudi, Hubei Province, exhibited severe deterioration following glyoxal dehydration, with approximately 30% of the surface area showing detached or curling lacquer films and the remaining fragments reduced to ~0.1 mm thickness with pronounced fragility. [3.6 Case Study]
Author Response
Comment 1：:Supplement this table caption with info if these are model samples or real samples.
Response
Revised：2.4.Characterization Methods explicitly states that all measurements were conducted on laboratory-prepared fir wood model specimens. This clarification avoids misunderstanding that historical artifacts were directly tested.
Comment 2：Mold growth evaluation is subjective and lacks methodological transparency. Include figures or provide more precise methods.
Response 2：We fully agree. To improve objectivity and transparency: 1、 Defined criteria for “visible mold growth”. 2、 Added representative optical micrographs (new Figure 3) showing mold-contaminated and mold-free samples. These additions provide visual and methodological evidence supporting the results.
Comment 3：No experimental tests were performed to assess removability or retreatability.
Response 3：Thank you for raising this important point regarding conservation ethics and material retreatability. We fully agree that reversibility is a key principle in many conservation contexts. However, for traditional East Asian lacquerware conservation, restoration practice typically prioritizes material compatibility and consistency with original techniques rather than complete removability.
In Chinese lacquer conservation, the principle of “repairing the old as the old” emphasizes the use of chemically and technologically compatible materials—namely natural lacquer itself—to maintain historical authenticity and long-term stability. Because cured lacquer forms a crosslinked polymer network similar to the original coating, complete reversibility is generally not achievable or expected, even in traditional practice. Instead, compatibility, stability, and retreatability (i.e., the possibility of partial softening and re-treatment without damaging the artifact) are considered more realistic and appropriate criteria.
Comment 4：: Shift orthogonal design details and Table 1 into Methods.
Response 4：:Completed. All orthogonal design details, factor levels, and preparation steps are now located in Section 2 (Materials and Methods). The Introduction retains only a brief summary sentence.
Comment 5：:Specific wording improvements.
Response 5：:All suggested sentences have been adopted or refined. The Abstract, Background, Experimental Design, Preparation, Acid Resistance, Moisture Resistance, XPS discussion, and Case Study sections have been linguistically polished accordingly. A new reference (Kosel et al., Journal of Cultural Heritage) has also been added to support mold evaluation methodology.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript entitled “Novel Adhesive Film for Glyoxal-Dehydrated Lacquerware: Composite Modification of Natural Lacquer with Soy Protein Isolate and Nano-SiO₂” presents a well-designed and scientifically sound study addressing a relevant problem in cultural heritage conservation. The authors propose a bio-based, nano-reinforced lacquer adhesive tailored for glyoxal-dehydrated lacquerware and validate its performance through systematic experiments and a real restoration case study.
The topic fits well within the scope of Coatings, particularly in relation to functional coatings, bio-based materials, and conservation science. The experimental design is comprehensive, results are convincing, and the mechanistic discussion is generally appropriate. However, the manuscript requires moderate language polishing and editorial corrections to meet MDPI’s publication standards.
Scientific merit: the study is original and relevant, especially in the context of conservation materials adapted to acidic environments caused by glyoxal dehydration. The orthogonal experimental design and multi-scale characterization (mechanical, chemical, microstructural) are strengths. The inclusion of a real artifact restoration case significantly enhances practical relevance.
Structure and clarity: the manuscript is logically structured, and, in my opinion, follows a standard journal format. Figures and tables are generally informative; however, figure numbering and formatting are inconsistent in places (see detailed comments).
Interpretation and mechanism: the proposed synergistic mechanisms involving Tween-20, SPI, and nano-SiO₂ are plausible and supported by FTIR/XPS evidence. Some mechanistic claims (e.g., Schiff base formation with glyoxal) should be more cautiously phrased or explicitly stated as hypotheses.
The discussion appropriately acknowledges reversibility limitations and aligns the material choice with conservation ethics. Sustainability considerations are a positive addition.
Minor Comments and language/editorial issues
Line 2: “ovel Adhesive Film” suggested change to “Novel Adhesive Film” (missing initial letter).
Line 5: Inconsistent spacing and punctuation between author names (e.g., “4and Wei Shuya” suggested change to “4 and Wei Shuya”).
Lines 6-11: Several affiliations lack consistent spacing, for example before postal codes (e.g., “430077China” suggested change to “430077, China”).
Lines 19-20: “no mold growth” - acceptable, but consider “no visible mold growth” for clarity.
Line 24: “Warring States period lacquer ear cup” - acceptable, but consider adding “(China)” for international readership.
Lines 36-37: “glyoxal dehydration technology has been widely adopted” consider “has been widely adopted in China” (if applicable) to avoid overgeneralization.
Line 42: “reduces the bonding performance” suggested change to “reduces the bonding performance of” (missing object clarity).
Line 121: “12 nm particle size” suggested change to “12 nm average particle size” (clarity).
Line 126: “L₉(3⁴)” - consider adding “Taguchi” for clarity to non-specialists.
Line 130: The Table 1 caption is missing a period at the end.
Line 166: “Figure2.Surface” suggested change to “Figure 2. Surface” (missing space).
Line 187: Table 2 caption: “Data presented as mean ± SD (n).” specify “(n = 5)” for clarity.
Figures 3-5 are referenced out of numerical order in the text; please ensure sequential consistency.
Lines 155-156: “58% enhancement” suggested change to “a 58% enhancement”.
Line 161: missing space after comma: “25°,Figure2.)” suggested change to “25°, Figure 2)”.
Lines 295-297: “Formulation optimization through orthogonal experimental design identified optimal composition” stylistically heavy; consider splitting into two sentences.
Line 300: “198% increased elongation” suggested change to “198% increase in elongation”.
Kind regards!
Author Response
Comment 1 ：Line 2: “ovel Adhesive Film” → “Novel Adhesive Film”.
Response 1：Corrected as suggested. The missing initial letter has been restored.
Comment 2：Line 5: Inconsistent spacing and punctuation between author names (e.g., “4and Wei Shuya”).
Response 2：Revised. Spacing and punctuation between all author names have been standardized.
Comment 3：Lines 6–11: Affiliations lack consistent spacing before postal codes.
Response 3：Corrected. All affiliations now follow the format “City Postal Code, Country” with consistent spacing (e.g., “430077, China”).
Comment 4：Lines 19–20: Replace “no mold growth” with “no visible mold growth”.
Response 4：Revised accordingly. The phrase has been changed to “no visible mold growth” for clarity and consistency with microbiological assessment standards.
Comment 5：Line 24: Add “(China)” after “Warring States period lacquer ear cup”.
Response 5：Added as suggested to improve clarity for international readers.
Comment 6: Lines 36–37: “widely adopted” → “widely adopted in China”.
Response 6：Revised. The sentence now specifies “widely adopted in China” to avoid overgeneralization.
Comment 7：Line 42: “reduces the bonding performance” → “reduces the bonding performance of”.
Response 7：Corrected. The object has been added for grammatical clarity.
Comment 8：Line 121: “12 nm particle size” → “12 nm average particle size”.
Response 8：:Revised to “12 nm average particle size” for accuracy.
Comment 9：Line 126: Add “Taguchi” before L₉(3⁴).
Response 9：Revised. The term “Taguchi orthogonal design” has been added for clarity to non-specialist readers.
Comment 10：Line 130: Table 1 caption missing period.
Response 10：Corrected. A period has been added.
Comment 11：Line 166: “Figure2.Surface” spacing issue.
Response 11：Corrected to “Figure 2. Surface”.
Comment 12：Line 187: Specify sample number in Table 2 caption.
Response 12：Revised. The caption now reads “Data presented as mean ± SD (n = 5)”.
Comment 13：Figures 3–5 referenced out of numerical order.
Response 13：Corrected throughout the manuscript.
Comment 14：Lines 155–156: “58% enhancement” → “a 58% enhancement”.
Response 14：Corrected throughout the manuscript.
Comment 15：Line 161: Missing space after comma.
Response 15：Corrected.
Comment 16：Lines 295–297: Sentence stylistically heavy; split into two sentences.
Response 16： Rewritten into two shorter sentences to improve readability.
Comment 17：Line 300: “198% increased elongation” → “198% increase in elongation”.
Response 17：Corrected throughout the manuscript.
Round 2
Reviewer 2 Report
Comments and Suggestions for Authors/
Author Response
Dear Reviewer,
We sincerely appreciate the time and effort you have dedicated to reviewing our manuscript. We are delighted to learn that you are satisfied with the revisions we have made in response to your previous remarks. Your insightful comments have significantly improved the quality of our work, and we are grateful for your constructive feedback.
Thank you once again for your support and guidance throughout this process.
Kind regards,
Reviewer 3 Report
Comments and Suggestions for AuthorsDear Authors,
thank you very much for addressing the remarks listed in the review.
No more other remarks from my side.
Kind regards!
Author Response
Dear Reviewer,
We sincerely appreciate the time and effort you have dedicated to reviewing our manuscript. We are delighted to learn that you are satisfied with the revisions we have made in response to your previous remarks. Your insightful comments have significantly improved the quality of our work, and we are grateful for your constructive feedback.
Thank you once again for your support and guidance throughout this process.
Kind regards,
