Saturation Failure
Chemical deficiency occurring when the treatment fluid fails to reach the center of a dense yarn package or fabric roll. Core liquor starvation results in uneven dyeing where the inner layers of the substrate are lighter than the exterior. The problem is generally detected during the unrolling or unwinding of the material after the drying stage.
Pressure Gradient
Resistance to flow is highest at the middle of a tightly wound beam. If core liquor starvation occurs, the innermost layers are deprived of the necessary concentrations of dye, bleach, softener or finish. This problem is more frequent in high-density packages where the winding tension is too high for the pump pressure to overcome.
Reversing Flow
Reversing the pump speed can sometimes force the liquid through the compact layers. When core liquor starvation persists despite high pressure, the machine may require a change in the flow direction from the inside out to the outside in. This cycling helps to distribute the chemicals more evenly, but it cannot always compensate for a package that is wound too hard at the start.
Package Density
Winding tension on the perforated tube determines the permeability of the substrate. Success in deep penetration depends on the immediate removal of air from the fibre interstices. Air pockets trapped in the center create a physical block that leads to core liquor starvation by preventing the liquid from contacting the fibre.
Pre-treatment with vacuum systems or specialized wetting agents is common to ensure the liquor reaches every part of the load.
