Abstract
When cotton fabrics dyed with C. I. Reactive Black 5 were discharged by the two-step fixation of steaming at 102$^{\circ}C$ and baking at 170~19$0^{\circ}C$ using the discharge agents of $K_2$CO$_3$and BASB (50%), baking for 3 min or more distinctly improved the white dischargeability while increasing the temperature of baking did slightly. In this case overall white dischargeability was unsatisfactory. On the other hand, baking at 160~18$0^{\circ}C$ after steaming at 12$0^{\circ}C$ greatly improved the white dischargeability compared with steaming at 102$^{\circ}C$, and almost complete white discharge was accomplished by baking for 3 min at 18$0^{\circ}C$ after steaming for 8 min at 12$0^{\circ}C$. Thus, in order to obtain satisfactory discharge results, increasing the temperature of steaming to 12$0^{\circ}C$ is much more effective than increasing that of baking to 19$0^{\circ}C$. White dischargeability increased with increasing amounts of urea, while the amount of dischange agent did not have a significant effect. In colored discharge printing, the excellent colored discharge results were achieved by steaming at 12$0^{\circ}C$ and baking at 160~18$0^{\circ}C$, while the insufficient discharge due to steaming at 102$^{\circ}C$ resulted in lower values of lightness and chroma. Compared with the case of white discharge, both the discharge of ground color and the fixation of color can be enhanced by increasing the amount of $K_2$CO$_3$/BASB to 140/140 (g/kg), but only the discharge of ground color was enhanced by increasing the concentration of urea to 130 g/kg.