Comparison of poplar ( Populus sp.) veneer staining using natural dyes from dyer’s madder ( Rubia tinctorum L.) and dyer’s woad ( Isatis tinctoria L.)

This study aimed to determine the influence of dye extracts from dyer’s woad (Isatis tinctoria L.) and dyer’s madder (Rubia tinctorum L.), when applied with traditional mordants, on the colour of poplar veneers. The study addresses the limited understanding of how natural pigments interact with wood substrates, and the effect of mordants on colour development in sustainable wood finishing. Colour changes were quantified using the CIE Lab* system to map parametric differences before and after dyeing. Woad produced shifts towards blue–green hues, indicating incomplete indigo formation, whereas madder generated stable red-orange tones characteristic of anthraquinone pigments. Mordants significantly enhanced colour saturation and fixation for both dyes. These results demonstrate the effectiveness of applying natural dye – mordant systems to wood surfaces, highlighting their potential as a renewable, visually appealing alternative to synthetic colourants in eco-friendly finishing processes.