Novel methods for dyeing the epidermis of bamboo culms and their colour fastness

This study examined 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). The objective was to determine the optimum approach for endowing the bamboo culms with a fascinating brown colour without removing their epidermis, which would increase the economic value of bamboo products. Experimental results revealed that an excellent brown colour was obtained when bamboo culms were treated with 0.25% CI Basic Brown 4 solution in an 80 °C water bath for 60 min (H° values of 37.9, 25.0, and 25.7° respectively). In addition, alkali‐pretreated bamboo culms also exhibited a good brown colour dyeing when treated with 0.25% CI Basic Brown 4 at ambient temperature for 2 days (a* and b* values of 30.8 and 35.1 respectively). Furthermore, the use of an ultrasonic bath instead of a water bath can reduce the treatment time required for achieving an improvement in the effectiveness of brown colour dyeing of the bamboo epidermis. Results obtained from indoor light fastness tests demonstrated that more uniform dyeing and better colour fastness could be achieved by colour fixation post‐treatment with 1% glacial acetic acid.