Optimization of Process of Dyeing Alpaca Yarn Using Indigo Carmine (C.I. Natural Blue 2)

Abstract

Highlights: What are the main findings? A dyeing process for alpaca fiber using indigo carmine (C.I. Natural Blue 2) was optimized through a central composite design (CCD) based on response surface methodology (RSM), considering mordant concentration, temperature, and time as variables. The process exhibited a strong fit to a quadratic model, with a high coefficient of determination (R2 and adjusted R2 values exceeding 95%), despite some limitations in specific response regions. The fastness properties of the dyed fiber were acceptable according to the ISO gray scale, indicating a stable interaction between indigo carmine (C.I. Natural Blue 2) and alpaca fiber, which may be attributed to lasting chemical bonding facilitated by the process conditions. What are the implications of the main finding? The optimized dyeing process offers a more sustainable alternative for protein-based fibers such as alpaca by utilizing food-grade dyes like indigo carmine (C.I. Natural Blue 2) under controlled conditions. The resulting dyed fibers demonstrate consistent color intensity and acceptable durability, supporting the viability of this approach for Peruvian textile coloration. These findings may promote further investigation into compatible food-grade dyes and encourage their industrial application in dyeing technologies. As part of an implementation in the Peruvian textile industry, the use of different sources to obtain blue hues in alpaca fiber has taken on a prominent role. The present study investigated the optimization of the dyeing process of alpaca fibers using indigo carmine as dye. The methodology was based on a central composite design (CCD) and response surface methodology (RSM) with color strength (K/S) as response variable. The results demonstrate that the independent variables significantly affected the color strength (K/S). In this context, an increase in both mordant concentration (3.9887 g/L) and dyeing temperature (95 °C), coupled with lower exhaust time (30.0019 min), enhanced levels of superficial dye adsorption. Additionally, color fastness properties provided tolerable values according to the gray scale. In conclusion, the optimization of the dyeing process of alpaca fibers using indigo carmine enabled the achievement of a blue shade with satisfactory fastness properties in the fiber yarns.