Dyeing treatments for protecting colour and colour fastness of green bamboo culms

The effects of various dyestuffs and treatment conditions on the epidermis colour of ma bamboo (Dendrocalamus latiflorus), moso bamboo (Phyllostachys pubescens), and makino bamboo (P. makinoi) were examined to determine the most appropriate dyeing material and approach for endowing bamboo culms with a fascinating green colour without removal of their epidermis. Experimental results revealed that excellent green colour was obtained when the three species of bamboo culms were treated with 0.25% basic dyes in an 80 °C water bath for 30 min (a* values of −19.6, −15.4, and −16.0, respectively). Moreover, alkali pretreatment, though contributing to dyeing effectiveness, yielded bamboo culms with dim surface lightness of low L* values. Dye makino bamboo culms without colour fixation post-treatment changed from green to light green after indoor exposure for 1 year, exhibiting unstable indoor colour fastness. In contrast, colour fixation post-treatment was found to improve colour fastness of bamboo culms; in particular, treatment with 1% glacial acetic acid or 3% tannic acid achieved more uniform dyeing effectiveness and better indoor fastness. By inhibiting discoloration, the natural beauty of bamboo culm can be preserved and its service life can be extended.