ASTM E313 for Yellowness & Whiteness

The American Standards Test Methods (ASTM) defines whiteness and yellowness indices for paper, paint and plastic although it is widely used in many industries. The E313 Whiteness Index is used for measuring any near-white material. Conversely, the ASTM’s E313 yellowness index is used to determine the degree to which a sample’s color shifts away from an ideal white.

If you are looking for an index and have no recommendation, then E313 is an excellent scale to adopt for your product.

ASTM D1925 for Yellowness

The ASTM D1925 method was withdrawn in 1995, but this formula still provides useful information. This index is always calculated for C/2°, regardless what illuminant and observer are chosen. The focus of this index is on evaluation of transparent plastics. By definition, the theoretical “perfect white” has reflectance values of 100% across the visible spectrum with corresponding colorimetric values of L* = 100.00, a* = 0.00, and b* = 0.00. If a white item is near, but not perfectly, white, it may be darker (have a lower L* value), and possibly be slightly chromatic, either in the red-green dimension (a*) or in the yellow-blue dimension (b*).