Colour Measurement

Colour measurements are useful because:

• There is a very poor relationship between the colour of greasy wool and the colour achieved after scouring. Greasy colour is strongly affected by wool grease and dust, both of which can be removed by scouring.
• They provide predictability of the colour of the raw processed product so that repeatable dying of colours in tops, yarns and fabrics can occur.
• They minimise the impact of price discounts for greasy wool where the greasy colour is appraised as not white.
  

1. Measurement Process

Colour measurement is conducted on the same scoured and Shirley Analysed web used for Mean Fibre Diameter measurement. The web is presented to a spectrophotometer and the reflectance of light from the web is recorded. Natural light is made up of a range of different colours. The colour of the wool is determined by which of these colours is absorbed or reflected. The instrument is calibrated to a system universally used by paint and dye companies. The results are expressed as tristimulus values X, Y and Z. The colour is best expressed as Yellowness (Y-Z) units.

2. Range of Yellowness

Values for Yellowness can range from 7 to 18 units of Y-Z.

The majority of Australian fleece lines will fall in the range 7-12 units of Y-Z when scoured. The basic problem is that whilst a skilled appraiser may be able to detect a difference of 1 unit on the scoured wool, it is impossible to appraise these differences when the wool is in the greasy state.