Wood coloring by reactive stains

The appearance of interior wood products (e.g.: furniture and floors) is often the first criteria that affects customer’s interests while making a purchase. One way to diversify the colors and appearances of wood products is by using reactive stains. These coloring systems, consisting of aqueous solutions of metal salts, can penetrate wood and react with its phenolic compounds by forming metal complexes. The color of wood obtained depends on the type of phenolic compounds, type of metal salt, wood surface preparation, temperature, wood humidity, and others. In order to determine the relationship between the structural characteristics of the phenolic compounds and the color developed on wood surface, the polyphenols of two North American hardwood species were extracted and analyzed by different spectrophotometric methods and by liquid state phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy. The chromatic coordinates (CIELAB system) of wood colors obtained after application of reactive stains were compared for these hardwood species. A better knowledge of the reaction mechanisms and the factors influencing them, will allow the optimal use of these systems in wood finishing industries. Since the colored products are present in the wood structure, the wood grain appearance will be preserved or even be accentuated. Enhancing the natural and warm aspect of wood used in buildings interiors can contribute to the well-being of the consumers and promote furthermore the use of this biosourced material