Internal Saturation
Depth to which the sizing solution enters the interstices of the yarn bundle determines the internal bonding of the fibres. Sizing penetration is measured by examining the cross-section of the linen yarn under a microscope to see how far the starch has reached. If the solution only stays on the surface, the yarn may have a hard shell but a weak core.
Bundle Integrity
Proper movement of the size into the centre of the yarn holds the individual flax filaments together and prevents them from sliding past one another. Without adequate sizing penetration, the yarn will flatten or disintegrate under the pressure of the loom’s beat-up motion. This internal strength is particularly important for the high-tension environment of modern weaving.
Excessive penetration can make the yarn too stiff, while insufficient penetration leads to shedding of size and fibre during production. Control of the sizing box temperature and the squeeze roller pressure is necessary to hit the target depth for each linen grade.
Process Control
Adjusting the pressure of the squeeze rollers in the sizing machine allows the mill to dictate how much liquid is forced into the yarn. Achieving the correct level of sizing penetration ensures that the warp is both flexible and strong. Consistent application leads to a more uniform fabric quality and fewer weaving defects.
