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Article

Impact of Acacia and Tragacanth Gums on the Surface Characteristics of Traditional Wood-Supported Polychrome Paintings

by
Xiaochen Liu
1,2,
Yuemin Feng
3,
Meng Xia
2,
Xinyou Liu
1,2,*,
Emanuela Carmen Beldean
4 and
Yushu Chen
2
1
Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Nanjing Forestry University, Nanjing 210037, China
2
College of Furnishings and Industrial Design, Nanjing Forestry University, Nanjing 210037, China
3
Tubao Decorative New Materials Co., Ltd., Huzhou 313200, China
4
College of Furniture Design and Wood Engineering, Transilvania University of Brașov, 560003 Brasov, Romania
*
Author to whom correspondence should be addressed.
Coatings 2025, 15(11), 1233; https://doi.org/10.3390/coatings15111233
Submission received: 8 September 2025 / Revised: 6 October 2025 / Accepted: 14 October 2025 / Published: 22 October 2025
(This article belongs to the Section Functional Polymer Coatings and Films)
Browse Figures
Versions Notes

Abstract

Polychrome paintings on wooden artifacts are vital elements of cultural heritage, where plant-derived binders play a crucial role in color formation and durability. This study aims to systematically compare the chemical, optical, and surface characteristics of two traditional natural adhesives—acacia gum (AG) and tragacanth gum (TG)—to better understand their influence on the preservation and reproduction of wood-supported polychrome coatings. Fourier-transform infrared spectroscopy (FTIR) confirmed their polysaccharide-rich structures, with distinct ester and glycosidic linkages, while rheological tests demonstrated that TG exhibited higher viscosity at 1–3% concentrations, whereas AG showed a sharper increase at 5%, reflecting different molecular architectures. Colorimetric analysis combined with two-way ANOVA revealed that gum type significantly influenced color development in blue and red coatings (p < 0.001), while yellow and green coatings remained largely unaffected. Gum concentration (1–5%) generally showed no significant effect on color. All coatings exhibited a matte appearance (<3 GU), with statistical analysis indicating that gloss was mainly determined by pigment particle distribution rather than adhesive type. Surface roughness increased notably with gum concentration (p < 0.001), demonstrating that binder content strongly affects coating microtexture. Overall, pigment type was the dominant factor for color, whereas gum concentration critically influenced surface morphology. These findings provide practical guidance for optimizing natural adhesives in the conservation of traditional polychrome artifacts.

1. Introduction

Polychrome painting is a significant form of traditional Chinese decorative art with a history spanning over two millennia. It evolved from the Pre-Qin period through the Tang and Song dynasties and became highly codified during the Ming and Qing dynasties [1]. As an important decorative practice in different civilizations, polychrome painting was widely applied to wooden architecture, sculptures, and murals in both Eastern and Western contexts, such as medieval European altarpieces, Burmese temples, and ancient Chinese palace decorations, serving primarily as an artistic and symbolic medium, while only partially fulfilling a protective role. Typically, a polychrome system consists of a ground layer over which one or more paintings are applied by mixing pigments and binders. Among the binders, plant gums such as tragacanth gum, arabic gum, and peach gum were frequently used owing to their abundance and strong adhesive properties [2,3,4,5]. However, gum-based coatings are vulnerable to environmental stresses including light, humidity, heat, and biological activity, which often result in fading, chalking, and flaking. These deterioration issues highlight the need for a systematic study [3,4,5,6].
Previous studies on polychrome wooden artworks—covering Egyptian [6,7], Mayan [8], Myanmar [9], European [10], and ancient Chinese examples [11,12]—have confirmed the critical binding role of plant gums and their influence on pigment adhesion and aging behavior. Recent works on watercolor and restoration materials based on gum arabic and other polysaccharide adhesives have further emphasized their relevance in conservation science [13,14,15]. Modern analytical techniques such as Fourier Transform Infrared Spectroscopy (FTIR), High-Performance Liquid Chromatography (HPLC), and Gas Chromatography–Mass Spectrometry (GC-MS) have been widely applied to investigate the composition and aging mechanisms of plant gums [16,17,18,19]. Findings indicate that different plant gums exhibit distinct stability and aging behaviors under environmental conditions, and that pigment type significantly influences gum film formation and degradation processes [20,21,22,23].
At the same time, evaluation methods for traditional paint systems have evolved considerably. Conventional microscopy and chemical testing have been complemented by spectroscopic analysis, Nuclear Magnetic Resonance (NMR), fluorescence imaging, and synchrotron radiation, providing detailed insights into microstructure, composition, and degradation mechanisms [24,25,26,27,28]. Despite these advances, systematic comparative studies of plant gums used in traditional paint layers remain limited, and the influence of environmental factors on their performance is still insufficiently understood. Such limitations hinder the development of reliable conservation strategies.
In conservation terminology, a “painting” refers to the artistic application of pigments bound in a medium to express aesthetic intent, while a “coating” typically denotes a protective or functional film. In this study, the term paint coating or paint layer refers to reconstructed layers that simulate the original appearance and surface behavior of historical polychrome paintings on wood.
To address these challenges, the present study investigates the effects of two plant-derived gums—acacia and tragacanth—on the physicochemical and surface behavior of wood-supported polychrome paint layers used in traditional artworks. By combining traditional pigments (vermilion, malachite green, yellow ochre, and lapis lazuli) with selected gums, the research systematically examines their physical and chemical characteristics, including color stability, microstructure, and surface features, using methods such as FTIR, rheological tests, and gloss and roughness measurements. The objective is to elucidate how gum structure and concentration influence the optical and surface properties of polychrome paint layers, thereby providing insights for the selection and optimization of natural adhesives in the conservation and reproduction of historical polychrome wooden artifacts. Ultimately, these findings aim to offer both theoretical guidance and practical references for cultural heritage conservation and materials research.

2. Materials and Methods

2.1. Materials

Natural plant gums, mineral pigments, and wooden substrates were employed in this study to prepare traditional polychrome paintings. Two plant-derived gums were selected: acacia gum (purity ≥ 99%) and tragacanth gum (purity ≥ 98%), both supplied by Xi’an Tianmao Baoding Biotechnology Co., Ltd. (Xi’an, China). These gums were dissolved in deionized water to obtain solutions of 1%, 3%, and 5% (w/w). The wooden substrates consisted of pinewood plates (100 mm × 100 mm × 8 mm, 10 ± 2% moisture content) without visible defects, supplied by Fuchuan Yao Autonomous County Caiyuan Wood Processing Factory, China, with a total of 60 substrates used. Four natural mineral pigments were adopted, all supplied by Yongzhou Shizhicolor Industrial Pigment Co., Ltd., China: lazurite (14# grade, deep-blue powder, 200 g), orpiment (As2S3, yellow powder, 200 g), malachite (Cu2CO3(OH)2, light green powder, 200 g), and vermilion (HgS, purity ≥ 99%, particle size ≤ 50 μm, 200 g). All pigments were stored in sealed, light-protected containers under dry conditions. The choice of traditional pigments and gums was guided by their historical significance in East Asian polychrome artworks [29].

2.2. Preparation of Polychrome Paintings

The preparation of polychrome paintings involved three main steps: gum solution preparation, pigment–gum mixing, and coating deposition. For the adhesive solutions, acacia gum and tragacanth gum were weighed and dissolved in deionized water to prepare concentrations of 1%, 3%, and 5% (w/w). The deionized water was maintained at room temperature (25 ± 1 °C) during dissolving. The mixtures were manually stirred at an equivalent rate of 500 rpm for 1 h, and then left to stand until bubble-free. The degassing process generally required between 30 and 45 min, depending on gum type and concentration, and always less than 60 min. Each mineral pigment, including lazurite, orpiment, malachite, and vermilion, was subsequently mixed with the adhesive solutions at a 1:1 mass ratio and stirred manually for 30 min until homogeneous pastes without visible aggregates were obtained. The pinewood substrates were pretreated by sanding with 400-grit abrasive paper and cleaning with anhydrous ethanol, then conditioned in a constant temperature–humidity chamber (25 °C, 50% RH) until reaching constant weight. The pigment–gum pastes were evenly applied onto the wood surface using a coating bar, with a controlled thickness of 0.15 ± 0.02 mm verified by a digital micrometer. For each formulation (gum type × concentration × pigment), three replicate samples were prepared, resulting in a total of 72 specimens, and all samples were naturally dried under dark conditions (25 ± 1 °C, 50% ± 5% RH) for 72 h to obtain stable coating films.

2.3. Characterization of Plant Gums

To evaluate the intrinsic properties of the plant-derived adhesives, two analytical methods were employed. Fourier-transform infrared spectroscopy (FTIR, Nicolet iS10, Thermo Fisher Scientific, Waltham, MA, USA) was used to characterize the functional groups of acacia gum and tragacanth gum in their solid states, with spectra collected in the range of 4000–400 cm−1 at a resolution of 4 cm−1. Additionally, the viscosity of gum solutions with different concentrations (1%, 3%, and 5% w/w) was measured using a digital viscometer (NDJ-5S, Shanghai Precision Instrument Co., Ltd., Shanghai, China) at 25 °C. Each measurement was repeated three times to ensure accuracy, and the results were recorded as mean values. FTIR and viscosity testing are standard tools for evaluating gum molecular structures and rheological behaviors, which are essential for understanding their performance as binders [30].

2.4. Evaluation Methods

2.4.1. Appearance and Color Evaluation

To compare the effects of gum type and concentration on the surface appearance and color of the coatings, one representative specimen from each group was scanned using a Canon CanoScan LiDE 400 flatbed scanner (Canon Inc., Tokyo, Japan). From each scanned image, a 1 cm × 1 cm region was cropped for direct visual comparison.
The chromatic parameters of the paintings were determined using a colorimeter (HP-200, Shanghai Hanpu Co., Ltd., Shanghai, China) under standard illuminant D65 and a 10° observer angle. The CIE Lab* color space values were recorded at five random points on each coating surface, and the average values were used for further analysis. The overall color difference (ΔE) was calculated relative to a white standard plate according to the CIE76 formula [31].

2.4.2. Gloss Evaluation

The surface gloss of the paintings was evaluated using a 3rh intelligent glossmeter (NHG268, Shenzhen 3nh Technology Co., Ltd., Shenzhen, China) at an incident angle of 60°. Three measurements were performed on each sample, and the mean values were reported. Gloss testing is a standard approach for evaluating differences in reflectance and surface finish between acacia and tragacanth gum coatings in heritage studies [32].

2.4.3. Surface Roughness Evaluation

The surface roughness (Ra) of the paintings was measured with a JB-4C roughness tester (Taiming Optical Instrument Co., Ltd., Shanghai, China). Measurements were conducted along three randomly selected positions on each specimen surface, and the average values were taken to represent the roughness characteristics. Roughness values provide insight into the effect of pigment morphology and binder type/concentration on coating microtopography [33].

2.5. Statistical Analysis

All experiments were conducted in triplicate, and the results were statistically analyzed using SPSS 25.0 software (IBM, Armonk, NY, USA). Two-way analysis of variance (ANOVA) was applied to evaluate the effects of gum type and concentration, as well as their interaction, on the measured parameters. When appropriate, Tukey’s post hoc test was used for pairwise comparisons. A p-value of less than 0.05 was considered statistically significant [34,35].

3. Results

3.1. Physicochemical Properties of Plant-Derived Gums

Figure 1 presents the FTIR spectra of acacia gum and tragacanth gum. For tragacanth gum, the characteristic absorption bands were observed at 3301 cm−1 (O–H stretching vibration), 2885 cm−1 (C–H stretching), 1607 cm−1 (C=O or aromatic skeletal vibration), 1398 cm−1 (C–H bending), 1227 cm−1 (C–O–C stretching of glycosidic linkages), 1020 cm−1 (C–O stretching in polysaccharides), and 802 cm−1 (C–H bending). In comparison, acacia gum exhibited similar bands but showed one additional distinct peak at 1324 cm−1, corresponding to C–O stretching [36,37].
Both gums displayed polysaccharide-related absorptions, confirming their carbohydrate-rich compositions. These spectra do not directly indicate water solubility; rather, they demonstrate that the gums are polysaccharide-based. The observed differences, particularly the additional peak at 1324 cm−1 in acacia gum, highlight subtle variations in ester groups and glycosidic linkages between the two gums, reflecting differences in their molecular structures. Similar FTIR profiles of plant gums have been reported in previous studies and publicly accessible spectral databases [38,39].
Figure 2 shows the viscosity of gum solutions at different concentrations. For acacia gum, viscosities increased sharply with concentration, measured as 198 mPa·s at 1%, 3831 mPa·s at 3%, and 22,946 mPa·s at 5%. For tragacanth gum, viscosities were 2425 mPa·s at 1%, 14,160 mPa·s at 3%, and 19,890 mPa·s at 5%. Both adhesives exhibited a clear positive correlation between concentration and viscosity, indicating strong concentration-dependent rheological behavior. Notably, tragacanth gum exhibited significantly higher viscosity than acacia gum at comparable concentrations, suggesting a denser molecular structure and stronger intermolecular interactions [40,41].

3.2. Color Characteristics of Polychrome Paintings

Representative scanned images of the painted specimens are presented in Figure 3, providing a direct visual comparison of surface appearance for different pigments prepared with acacia gum and tragacanth gum. These images highlight the overall visual differences before quantitative evaluation.
The detailed chromatic parameters obtained by colorimetric analysis are shown in Figure 4. For the blue paintings (Figure 4a), acacia gum produced a slightly darker tone (L* = 61.40) and stronger saturation (C* = 20.80) compared with tragacanth gum (L* = 67.04, C* = 16.88). The corresponding a* values were −3.29 (acacia gum) and −4.31 (tragacanth gum), while b* values were −20.53 and −16.32, respectively, confirming the bluish hues, with acacia gum yielding a deeper and more vivid tone. In the yellow paintings (Figure 4b), both gums gave very similar results, with high lightness (L* ≈ 83), strong chroma (C* ≈ 67–68), and consistent hue. The a* values were 10.82 (acacia) and 9.99 (tragacanth), and b* values were 65.76 and 67.37, indicating that gum type had little effect on the stability of yellow tones.
For the green paintings (Figure 4c), acacia and tragacanth gums yielded nearly identical colorimetric values. Lightness remained around L* ≈ 76, chroma at C* ≈ 24, with negative a* values (−22.24 and −21.68) and positive b* values (10.62 and 10.30), corresponding to stable green hues independent of gum type. In the red paintings (Figure 4d), both gums produced moderate lightness (L* ≈ 50) and high saturation. However, tragacanth gum showed slightly higher chroma (C* = 53.40) compared with acacia gum (C* = 50.42). The a values were strongly positive (45.77 and 48.20), and b* values were also positive (21.14 and 22.94), indicating vivid red-orange colors, with tragacanth gum yielding a slightly more intense appearance [42].
As shown in Figure 4 and Table 1, gum type had a significant influence on color development in the blue and red paintings, where differences in L*, a*, and b* values between acacia and tragacanth gums were highly significant (p < 0.001). In contrast, for the yellow and green paintings, gum type showed a significant effect only on the a* coordinate (p < 0.001), while L* and b* values were not significantly different (p > 0.05), indicating relatively stable chromatic behavior regardless of the gum employed. Concentration of plant gums (1%, 3%, and 5%) did not significantly affect colorimetric values in most cases (p > 0.05), except for the red paintings where concentration significantly influenced all three parameters (L*, a*, and b*, p < 0.001). No significant interaction between gum type and concentration was observed across most color groups, suggesting that their effects were largely independent. These results demonstrate that pigment type was the dominant factor determining coating color, while gum type modified chromatic expression in specific pigments, particularly blue and red. By contrast, gum concentration played only a limited role, influencing red coatings but showing negligible effects on yellow and green.

3.3. Gloss Analysis of Polychrome Paintings

The gloss values of the polychrome paintings prepared with acacia gum and tragacanth gum at different concentrations are shown in Figure 5. All samples exhibited low gloss levels, ranging from 0.7 to 2.9 GU, which is consistent with traditional matte finishes. Statistical analysis via two-way ANOVA (Table 2) revealed that the effects of gum type and concentration were pigment-dependent. For blue paintings, only concentration had a significant effect (p = 0.014), while for yellow paintings, neither factor nor their interaction was significant. In contrast, both green and red paintings showed highly significant effects for both gum type (p = 0.019 and p = 0.005, respectively) and concentration (p < 0.001 for both).
Where the ANOVA indicated significant effects, a post hoc Tukey’s test was conducted. The results of these pairwise comparisons are indicated by lowercase letters above each bar in Figure 5, where bars sharing the same letter are not significantly different (p < 0.05). To facilitate visual comparison between acacia gum and tragacanth gum, the y-axis scale was standardized to 0–4 GU for both graphs. The updated Figure 5 presents the gloss values of the polychrome paintings prepared with different gum types and concentrations, clearly showing the statistical groupings identified by Tukey’s test.

3.4. Surface Roughness Analysis of Polychrome Paintings

The surface roughness parameters (Ra, Rq, and Rt) of the polychrome coatings prepared with acacia gum and tragacanth gum are presented in Figure 6. The results of a two-way ANOVA analyzing the effects of gum type and concentration are summarized in Table 3.
Statistical analysis revealed that the significance of these factors was highly dependent on both the pigment color and the specific roughness parameter. For blue paintings, neither gum type nor concentration had a significant effect on any of the three roughness parameters (p > 0.05 for all). Similarly, for yellow paintings, while gum type had a significant effect on Ra (p = 0.045), no other significant effects were observed for Rq or Rt. In contrast, for green paintings, concentration was a highly significant factor (p < 0.001) for Ra, Rq, and Rt, whereas gum type and the interaction were not significant. The most pronounced effects were seen in red paintings, where both gum type and concentration had a highly significant influence on Ra (p < 0.001 for both), and concentration also significantly affected Rq (p = 0.041) and Rt (p = 0.002).
The images presented in Figure 6 are representative of the overall trends observed across all treatments. For cases where no significant differences were found (e.g., all parameters for blue paintings), the image reflects the average surface morphology common to all concentrations of that gum type. Where significant effects were identified, the image corresponds to the treatment that was most representative of the dominant trend, such as the concentration level that yielded the median roughness value. Overall, the data indicate that while pigment type is a primary determinant of surface topography, the influence of gum type and concentration is statistically significant for specific color-formulation combinations.

4. Discussion

This study demonstrates that the physicochemical and surface properties of traditional wood-supported polychrome paintings are determined by the combined effects of pigment composition, plant gum type, and binder concentration. FTIR analysis confirmed the polysaccharide nature of both acacia and tragacanth gums, and their molecular structure differences account for distinct rheological behaviors and film formation properties [43]. Tragacanth gum, with its highly branched macromolecular network, showed greater viscosity at low concentrations (1–3%), whereas acacia gum exhibited a sharper increase at 5% concentration due to chain entanglement and hydrogen bonding. Color development analysis revealed that gum type significantly influenced the chromatic behavior of blue and red paint layers, which can be attributed to pigment dispersion efficiency and differences in refractive index matching between pigment particles and binder matrices. In contrast, yellow and green paint layers were less affected by gum type, indicating the predominance of intrinsic pigment characteristics in determining their optical appearance. The limited impact of gum concentration (1–5%) on color confirmed that pigment properties outweigh binder effects in chromatic expression. Surface and optical analyses further indicated that all reconstructed paint films exhibited very low gloss values (<3 GU), consistent with the matte aesthetic of historical polychrome artworks. Statistical evaluation showed that both gum type and concentration affected gloss in the green and red samples, reflecting differences in binder viscosity and pigment packing. Surface roughness values (Ra, Rq, Rt) were notably higher than those typical of modern paint films (Ra < 0.5 μm), confirming the granular morphology of mineral pigments and the limited leveling ability of plant gums [44]. The roughness increase with gum concentration was attributed to viscosity-induced aggregation and reduced flowability during drying. The results emphasize that gum type primarily influences pigment dispersion and chromatic expression, while concentration controls surface morphology. From a conservation perspective, gum selection is most critical for reproducing historical color tones—particularly in blue and red pigments—whereas concentration adjustments mainly serve to fine-tune texture and gloss. For yellow and green pigments, the two plant gums perform comparably, allowing more flexible material choices. Future research will extend this study by incorporating microscopic pigment distribution analyses and accelerated aging experiments to evaluate long-term stability and to better simulate historical painting conditions. These investigations will help bridge material science data with practical guidelines for the restoration and reproduction of wood-supported polychrome paintings.

5. Conclusions

This study clarifies the influence of acacia and tragacanth gums on the physicochemical, optical, and surface characteristics of reconstructed wood-based polychrome paint layers. Both gums exhibited typical polysaccharide features but differed in molecular structure and viscosity behavior—tragacanth gum maintained higher viscosity at 1–3%, while acacia gum showed a sharper increase at 5%. Gum type significantly affected color development in blue and red paints, whereas yellow and green paints remained stable, and gum concentration had minimal influence on overall chromatic properties. All paint films exhibited a matte finish (<3 GU) consistent with historical visual qualities, with gloss and roughness mainly influenced by binder concentration. Higher gum concentrations increased surface roughness due to reduced flow and increased pigment aggregation. These findings indicate that pigment type dominates the visual appearance, while gum type and concentration modulate secondary effects such as hue intensity, gloss, and surface texture. The study contributes practical insights for heritage conservation by linking binder chemistry to aesthetic outcomes, offering reference data for the reconstruction and stabilization of traditional polychrome wooden artworks. Future work involving accelerated aging tests and comparative studies with authentic historical paint samples will further verify these findings and provide a stronger basis for the long-term preservation of cultural heritage materials.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/coatings15111233/s1, Figure S1. Representative stereo microscope images of polychrome coatings prepared with acacia gum (AG) and tragacanth gum (TG) at different concentrations.

Author Contributions

Conceptualization, X.L. (Xinyou Liu) and Y.F.; methodology, X.L. (Xiaochen Liu) and M.X.; software, M.X.; validation, X.L. (Xiaochen Liu), Y.F. and Y.C.; formal analysis, X.L. (Xiaochen Liu); investigation, X.L. (Xiaochen Liu) and Y.C.; resources, Y.F. and E.C.B.; data curation, M.X.; writing—original draft preparation, X.L. (Xiaochen Liu); writing—review and editing, X.L. (Xinyou Liu) and E.C.B.; visualization, M.X.; supervision, X.L. (Xinyou Liu); project administration, X.L. (Xinyou Liu); funding acquisition, Y.F. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported by the Scientific Research Contract (No. 11295) from Transilvania University of Brasov, dated 12 August 2025.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in this study are included in the article/Supplementary Material. Further inquiries are available from the corresponding author, [X.L.], upon reasonable request.

Conflicts of Interest

Author Yuemin Feng was employed by the company Tubao Decorative New Materials Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Coatings 15 01233 g001
Figure 1. FTIR spectra of two plant-derived gums.
Figure 1. FTIR spectra of two plant-derived gums.
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Figure 2. Viscosity determination results of two glues at different concentrations.
Figure 2. Viscosity determination results of two glues at different concentrations.
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Figure 3. Scanned images of polychrome painting specimens prepared with acacia gum and tragacanth gum.
Figure 3. Scanned images of polychrome painting specimens prepared with acacia gum and tragacanth gum.
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Figure 4. Color coordinate values (L*, a*, b*, C*) of polychrome paintings prepared with acacia gum and tragacanth gum: (a) blue paintings, (b) yellow paintings, (c) green paintings, (d) red paintings.
Figure 4. Color coordinate values (L*, a*, b*, C*) of polychrome paintings prepared with acacia gum and tragacanth gum: (a) blue paintings, (b) yellow paintings, (c) green paintings, (d) red paintings.
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Figure 5. Gloss values of polychrome paintings prepared with different concentrations of (a) acacia gum and (b) tragacanth gum adhesives using four mineral pigments. Columns with different lowercase letters (a, b, c) are significantly different (p < 0.05, Tukey’s post hoc test).
Figure 5. Gloss values of polychrome paintings prepared with different concentrations of (a) acacia gum and (b) tragacanth gum adhesives using four mineral pigments. Columns with different lowercase letters (a, b, c) are significantly different (p < 0.05, Tukey’s post hoc test).
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Figure 6. Surface roughness parameters (Ra, Rq, and Rt) of polychrome coatings prepared with (a) acacia gum and (b) tragacanth gum at different pigment types.
Figure 6. Surface roughness parameters (Ra, Rq, and Rt) of polychrome coatings prepared with (a) acacia gum and (b) tragacanth gum at different pigment types.
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Table 1. Results of two-way ANOVA for CIELAB color coordinates (L, a, b*) of polychrome paintings prepared with acacia gum and tragacanth gum at different concentrations.
Table 1. Results of two-way ANOVA for CIELAB color coordinates (L, a, b*) of polychrome paintings prepared with acacia gum and tragacanth gum at different concentrations.
Painting Type Color CoordinatesGum TypeConcentrationGum Type × Concentration
Blue paintingL*<0.0010.7460.879
a*<0.0010.7830.798
b*<0.0010.7640.769
Yellow paintingL*0.0690.7030.853
a*<0.0010.7840.744
b*0.0590.5660.624
Green paintingL*0.2440.8750.896
a*<0.0010.4560.677
b*<0.0010.6320.745
Red paintingL*<0.001<0.001<0.001
a*<0.0010.1240.215
b*<0.0010.2370.267
Table 2. Results of two-way ANOVA for polychrome paintings gloss prepared with acacia gum and tragacanth gum at different concentrations.
Table 2. Results of two-way ANOVA for polychrome paintings gloss prepared with acacia gum and tragacanth gum at different concentrations.
Painting TypeGum TypeConcentrationGum Type × Concentration
Blue painting0.3240.0140.916
Yellow painting0.4120.7390.761
Green painting0.019<0.0010.373
Red painting0.005<0.0010.916
Table 3. Results of two-way ANOVA for polychrome paintings surface roughness prepared with acacia gum and tragacanth gum at different concentrations.
Table 3. Results of two-way ANOVA for polychrome paintings surface roughness prepared with acacia gum and tragacanth gum at different concentrations.
Painting TypeRoughnessGum TypeConcentrationGum Type × Concentration
Blue paintingRa0.4400.3580.099
Rq0.9700.1590.588
Rt0.8220.6990.787
Yellow paintingRa0.0450.5080.484
Rq0.2460.1360.685
Rt0.8190.1950.814
Green paintingRa0.618<0.0010.549
Rq0.879<0.0010.918
Rt0.959<0.0010.849
Red paintingRa<0.001<0.0010.650
Rq0.5380.0410.597
Rt0.9260.0020.773
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Liu, X.; Feng, Y.; Xia, M.; Liu, X.; Beldean, E.C.; Chen, Y. Impact of Acacia and Tragacanth Gums on the Surface Characteristics of Traditional Wood-Supported Polychrome Paintings. Coatings 2025, 15, 1233. https://doi.org/10.3390/coatings15111233

AMA Style

Liu X, Feng Y, Xia M, Liu X, Beldean EC, Chen Y. Impact of Acacia and Tragacanth Gums on the Surface Characteristics of Traditional Wood-Supported Polychrome Paintings. Coatings. 2025; 15(11):1233. https://doi.org/10.3390/coatings15111233

Chicago/Turabian Style

Liu, Xiaochen, Yuemin Feng, Meng Xia, Xinyou Liu, Emanuela Carmen Beldean, and Yushu Chen. 2025. "Impact of Acacia and Tragacanth Gums on the Surface Characteristics of Traditional Wood-Supported Polychrome Paintings" Coatings 15, no. 11: 1233. https://doi.org/10.3390/coatings15111233

APA Style

Liu, X., Feng, Y., Xia, M., Liu, X., Beldean, E. C., & Chen, Y. (2025). Impact of Acacia and Tragacanth Gums on the Surface Characteristics of Traditional Wood-Supported Polychrome Paintings. Coatings, 15(11), 1233. https://doi.org/10.3390/coatings15111233

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