Laser Induced Dyeing (LID) with Reactive Blue 21 on Hemp Fibers

Effects of 532 nm and 320 mJ laser beam on aqueous solution of Reactive Blue 21 (RB21), a copper based on reactive dye, have been studied in both presence and absence of garnet gemstone with the aim to receive a proper coating of the hemp fibers contained in the yarns of a woven texture while reducing the dyeing time compared to the classic exhaustion dyeing method. Results show that both laser beam and garnet influenced the dyeing process with RB21, enhancing the absorption and reaction of RB21 with the composite structured hemp fibers, effect observed in the color intensities for all samples measured with the grayscale. The best results are noticed for laser effects in presence of garnet gemstone when highest coating is achieved among all samples, and the process is 11 times shorter than the classical exhausting method. Compared FTIR and UV-VIS spectra of initial dyestuff and residual dyestuff isolated from the wastewaters offered information about dyestuff exhaustion process under garnet and/or laser influence. Laser Induced Fluorescence completed the study with the information about RB21 behavior under UV laser beam of 362 nm.