Woollen-spun wool products
The objectives of finishing include:
- Making the fabric or garment dimensionally stable, by the relaxation of stains and tensions imposed during manufacturing.
- Removing additives including oils and lubricants, which were applied earlier on in manufacturing in order to assist processing. In comparison to worsted-spun products, woollen-spun products usually contain a significantly high percentage of processing aids. Therefore it is essential that woollen-spun products undergo wet-finishing as opposed to dry finishing which relies upon steam pressing only.
- Improving both the appearance and hand feel. For woollen-spun products this normally involves a milling process - controlled washing. This consolidates the fabric structure, allowing yarns to swell and burst and for some of the fibres to protrude from the fabric surface, giving woollen products their characteristic milled (hairy) appearance. Milling is also sometimes complemented by mechanically brushing or raising of the fabric surface.
- Making the garments “fit for purpose” and “ready for sale”.
- Provides an opportunity to add “added value” finishes such as showerproofing and anti-microbial.
Conducting finishing at optimum conditions and in a controlled manner is essential to ensure consistency; otherwise it is likely to have an adverse effect on wear and laundering performance, as well as the handle and appearance of the final product.
The finishing of woollen products usually comprises the following main stages: scouring, milling, rinsing, drying and dry finishing. In some cases the scouring and milling operation may be combined.
Scouring and Milling
Both scouring and milling involves washing the fabrics or garments in a controlled manner, in warm water containing detergent. Sometimes alkali is added to the solution to assist in better removal of processing oils.
The purpose of scouring is to remove the high amount of processing oils present, and any contaminants such as dirt or soil which may have been picked up during the manufacturing process. Without adequate removal of the processing oils the fabric would still have an unpleasant greasy feel. In addition, a high amount of residual remaining could lead to it eventually becoming oxidized, taking on a rancid smell. The Woolmark Company’s specification measures as percentage Total Fatty Matter (%TFM) is < 1.5 % TFM remaining.
The milling stage is to consolidate the fabric’s structure. During the knitting process, woollen yarns are loosely knit, and similarly woven fabrics are woven in a more open or loose a weave, allowing for consolidation of the fabric structure to take place. In addition, the washing action (mechanical action), exerts forces on the fabrics or garments which result in fibres starting to migrate from the surface of the fabric, resulting in a milled appearance which is characteristic of woollen-spun products.
Fabrics or garments are thoroughly rinsed in clean water after the scouring and milling operations before drying.
After drying the fabrics or garments they may be subjected to mechanically brushing or raising. This further develops or accentuates the desired milled appearance, before been pressed to improve their dimensional stability properties.