Single Number Shade Passing in Yarn Package Dyeing

In a modern yarn package dyeing operation, where blind—dyeing techniques are extensively used, an effective, but critical, system of quality control is necessary so that dyelots are examined before they are unloaded from the dyeing frames for subsequent processing. This quality control system depends on sampling a number of packages throughout the dyelot and comparing these against the standard for shade and levelness. With the installation of a colour physics package, the examination of these swatches can be carried out instrumentalfy rather than by visual means. The work described was carried out on an I. C. S. Colour Physics package using theJPC 1979 formula [2] as the pass/ fail program. The outstanding feature of this program is that it does not require tolerances to be set out for individual colour centres. Instrumental and visual assessments on a large number of shades for various end—uses have been compared and good agreement between the two methods has been obtained. It has been possible to set up a pass/fail colour tolerance for a number of end—uses based on a single number, i. e. ΔE. It is likely that instrumental methods will eventually replace completely the current visual shade passing of package—dyed yarn. The use of non-physical standards is also being investigated.