Hunter Lab colorimeter

Once washed, the swatches are read on a Hunter Lab Colorimeter for reflectance (L), redness/greenness (a), and yeUowness/blueness (b) values. The reflectance is used to calculate percent soil removed (% SR) which ranges from 0 to 100. Whiteness index (Wl) [17] and yellowness index (Y2) can also be determined. The whiteness scale ranges from 0 (black) to 100 (white). The yellowness index ranges from positive (yellow) to negative (blue). To determine how much soil is removed from the fabric, see Figure 2. 

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