Chevron Phillips Index for Yellowness

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FAQ: “As mentioned on the phone yesterday, currently Chevron Philips is interested in a unit of D25LT. However, Chevron has been using a test known as the Philips Index for their color measurement. Do you know that if we can input this Philips index into their D25LT?

The formula is as follows:

Chevron Phillips Index = [(2Z - (X + Y))*10] for C/2 conditions

This index is calculated for Illuminant C/2 Degree Standard Observer as the scale was implemented originally on tristimulus colorimeters.

The Chevron Phillips Index, also called "P color", is measured on plastic pellets, and would be typically implemented as a Custom Formula in EasyMatch QC.

FAQ: "What is the highest possible value for Chevron Phillips Index?"

For a perfect white material having no yellowness with the following CIE values - X = 98.074, Y = 100.00, Z = 118.23, C/2; Chevron Phillips Index = 383.86

 

C/2

   

C/2

C/2

 

X

Y

Z

YI D1925

Chevron Phillips Index

PRD Perfect White

98.074

100

118.23

0.21

383.86

TiO2 White Tile

82.27

84.46

97.46

2.37

281.90

Typical Pellets

72.21

74.28

85.46

2.48

244.30

It is recommended that after standardization, just leave the calibrated white tile at the port and measure it as a standard or sample. It should always read basically the same as Day 1 baseline within a unit in Chevron Phillips Index.

FAQ: “What Alternative Color Scale can be used that is similar if not equivalent?”

Alternative yellowness scales, such as YI D1925 C/2 or the equivalent YI E313 C/2 or YI E313 D65/10 should work equally as well in discerning small yellowness differences in plastic pellets.

 

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