Dyeing & finishingPrint
Dyeing may be carried out at a number of different processing stages.
Wool top, yarn, fabric and garments can all be dyed, with the selected method the one which best suits the processor’s requirements such as price and production lead times.
Finishing is an integral step in the manufacture of all wool products. How well it is done dramatically impacts upon the handle, appearance and wear performance of the final knitted garment.
Finishing aims to reduce or eliminate relaxation shrinkage, improve handle and appearance and remove any residual processing aids in knitted garments and fabrics.
Worsted-spun knitwear receives a very light wash and steam, whereas woollen-spun knitwear is washed more intensively to create the bulk and hairiness for which it is famous.
In woven fabrics finishing aims to relax and stabilise strains within the fabric that are introduced during spinning and weaving and remove any residual dirt, lubricants and waxes through washing. The typically smooth surface of a woven fabric is achieved by shearing-off surface fibres then pressing with high-temperature steam.
In both knitted and woven products finishing allows for the application of added value or functional finishes.
Research has concentrated on reducing the damage that dyeing causes to wool. This includes reductions in the time of dyeing, reductions in the temperature of dyeing and the application of chemicals to block the damaging chemical reactions.
Other developments have been in the dyes themselves. The aim has been to develop dyes that can be used on most substrates, using the same application methods. This simplifies the dyeing processes and reduces the inventory of dyes that dyehouse needs to hold.
Machinery developments have also taken place, the main advance being in the area of automation. Virtually all modern machines are equipped with microprocessors to control the main operations. Systems are also available, particularly for yarn dyeing, to use robotics to fully automate the dyeing process.