Fluid Flow
Measurement of the internal resistance to movement in a sizing solution determines how the chemical will behave when applied to flax yarns. Modified starch viscosity dictates the thickness of the coating and the ease with which it can be pumped through the sizing machine. This property is adjusted by varying the concentration of the starch or the temperature of the mix.
Penetration Depth
Thin solutions flow easily into the core of the yarn, while thick solutions tend to stay on the outer surface to form a film. Controlling modified starch viscosity ensures that the linen fibres are bonded together without becoming too stiff or brittle for weaving. Proper penetration provides the internal strength needed to survive the mechanical stresses of the loom.
Mills use brookfield viscometers to monitor the solution in the size box during the entire production run. Variations in the moisture content of the raw starch can cause unexpected changes in the flow characteristics of the size.
Stability Limit
Changes in the chemical structure of the starch prevent the solution from thickening too much as it cools. Maintaining a consistent modified starch viscosity throughout the entire sizing run prevents variations in the amount of size picked up by different sections of the warp. This uniformity is essential for producing a consistent fabric hand and appearance.
