Innovative critical solutions in the dyeing of protein textile materials

Even though animal fibres contribute a comparatively low proportion of world fibre production, they are highly sought after and play a significant role in the luxury, high value-added end of the market. Natural protein fibres have two major classes, which may be categorized as keratin fibres (hair or fur), such as wool, cashmere, and other animal hairs, and secreted (insect) fibres with silk as the main fibre in this category. Colouration of protein fibres is characterized by many variables, each with a different effect on the final product. Indeed it is quite complicated to achieve the intended colour in the first dyeing attempt. Dyeing defects are not always due to the actual dyeing process, but may be introduced in earlier production and processing stages. This work attempts to provide a detailed review of the major issues in the dyeing of various protein textile materials in different forms such as loose fibre, yarn, fabric, and garment. An overview of different types of protein fibres is given and a summary of current industrial practices for the dyeing of protein fibres is provided followed by key variables that affect the control of colour in the dyeing of protein fibres. Key steps and critical factors involved in the production of dyed protein textile materials are described in detail and solutions to the problems that may arise at each stage are provided.