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Color Variability of European Oak Veneer Packages: An Exploratory Colorimetric, Chemical, and X-Ray Diffraction Study
Edmund Smolarek1,2, Kinga Szentner3, Jarosław Jakubowicz4
1Balti Spoon OÜ, Kupu Küla, 74610 Kuusalu Vald, Harju Maakond, Estonia.
Molecules (Basel, Switzerland)
|August 13, 2026
Summary
Natural color variation in European oak veneers (Quercus robur and Quercus petraea) complicates sorting. Extractives content, not provenance alone, significantly impacts veneer lightness, suggesting combined analysis for quality control.
Area of Science:
- Wood science
- Materials science
- Forestry
Background:
- European oak (Quercus robur and Quercus petraea) is valued for decorative veneers.
- Natural color heterogeneity in oak veneers presents challenges for industrial sorting and package matching.
- Current sorting methods may not adequately account for inherent wood properties influencing color.
Purpose of the Study:
- To characterize color and chemical properties of European oak veneer packages from different commercial origins.
- To investigate the relationship between extractives, cellulose, lignin, crystallinity, and veneer color (CIELAB lightness).
- To assess the potential for using these characteristics for provenance-based sorting.
Main Methods:
- Visual assessment and CIELAB color measurements of veneer packages.
- Analysis of subsamples for ethanol-soluble extractives, cellulose, and lignin content.
- X-ray diffraction (XRD) analysis to determine cellulose crystallinity (CrI).
- Exploratory correlation and regression analyses (Pearson, Spearman) to link chemical/physical properties with color.
Main Results:
- Significant variation in lightness (L*) was observed both among and within veneer packages, with within-package ranges overlapping inter-package differences.
- Higher ethanol-soluble extractive content was strongly correlated with lower veneer lightness (negative association).
- Lignin and cellulose crystallinity showed weak or inconclusive associations with color in this exploratory study.
- XRD analysis confirmed cellulose I reflections, with approximate CrI values ranging from 48.0% to 66.2%.
Conclusions:
- Veneer color heterogeneity is substantial, making provenance-based sorting based solely on average package color unreliable.
- Ethanol-soluble extractives are a key factor influencing oak veneer lightness.
- Combined colorimetric and chemical characterization is recommended for package-level quality control.
- Further independent replication across multiple packages per region is necessary to validate geographic origin classifiers.
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