Yarn Irregularity
Thick, soft places in linen yarn occur naturally during the spinning of flax fibers due to their irregular lengths. In the textile industry, these thick sections are called slubs when they appear in either the warp or the weft yarn. This unevenness is often left in the yarn to give the fabric its characteristic textured appearance.
It can also cause problems during weaving if the thick spots are too large to pass through the reed.
Mechanical Origin
Spinning machines sometimes create these thick spots accidentally when the drawing rollers are not adjusted correctly. If the drawing speed is uneven, groups of fibers slip together, creating a local mass excess. When these spots occur in high numbers, they reduce the yarn strength because the twist is not distributed evenly.
This uneven distribution leads to thin, weak spots adjacent to the thick zones. Operators adjust the drafting zone to maintain the desired yarn count.
Fabric Grading
Quality inspectors count these thick spots on the finished fabric to determine if they meet the buyer’s requirements. Some linen products allow them for aesthetic reasons, while other fabrics require them to be minimal. It is necessary to monitor their size to prevent warp breakages during weaving.
