Natural dyes have attracted increasing attention as environmentally friendly alternatives to synthetic colorants in textile coloration. In this study, an ultrasound-assisted natural dyeing process using beetroot (Beta vulgaris L.) extract was developed for cotton fabrics, and the effects of ultrasonic power, dyeing temperature, and dyeing time on the color strength of dyed fabrics were systematically investigated. Response surface methodology based on a Box-Behnken experimental design was employed to evaluate the influence of these parameters and to determine the optimal dyeing conditions. The experimental results showed that the color strength (K/S value) of the dyed fabrics varied from 10.87 to 14.73 within the investigated experimental range. Analysis of variance indicated that the regression model was statistically significant and that ultrasonic power had the most pronounced influence on dye uptake. The optimal dyeing conditions were determined as ultrasonic power 230 W, dyeing temperature 70 °C, and dyeing time 60 min. Under these conditions, the predicted K/S value was 14.80, while the experimentally obtained value was 14.72, demonstrating good agreement with the model prediction. The results confirm that ultrasound-assisted dyeing combined with statistical optimization provides an effective approach for improving natural dyeing efficiency and promoting sustainable textile coloration technologies.

natural dye, ultrasonic dyeing, cotton fabric, response surface methodology, color strength