Contribution to understanding the color development on wood surfaces treated with iron salts by a combination of analytical methods

Abstract

Metal salts application on wood surface is a simple and nontoxic method that can be used for wood color modification, which is induced by the formation of colored complexes between wood extractives and metal ions. In this study, we have combined several analytical methods to understand the color development for four North American hardwood species: white oak, red oak, sugar maple and yellow birch. The phenolic composition of the ethanolic extracts of heartwood and sapwood of the four wood species was studied by UV-Vis spectrometry and liquid state phosphorus-31 nuclear magnetic resonance spectroscopy (31P NMR) and analyzed in relation to color development. The correlations between different OH types and the color development as measured with the CIEL*a*b* color coordinates, indicate that the descending order of correlation for phenolic hydroxyls was: di-substituted OH, mono-substituted OH and un-substituted OH while no correlation was found between COOH hydroxyls and total color change (ΔE).

Keywords:

• Hardwoods extractives
• iron salts
• wood staining
• UV-Vis spectrometry
• 31P NMR

Acknowledgments

The help with NMR analysis is gratefully acknowledged to Pierre Audet and Stéphanie Vanslambrouck. The authors are also grateful for the assistance of Yves Bedard, Luc Germain and Daniel Bourgault with lab work and wood samples preparation and Mr. Yannick Piriou of the DRT nutraceuticals for supplying the Oligopin^® sample.

Disclosure statement

The authors declare that they have no conflict of interest.

Funding

This research was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) through the PCI program and the industrial partners of NSERC/Canlak Industrial Research Chair in Interior Wood Products Finishes (CRIF) Canlak, Boa-Franc, EMCO-Inortech and Canadel (Grant No. PCIPJ 514918-16).