Meaning and Purpose
5.1 This practice should only be used to compare specimens of the same material and of the same general appearance. For example, a series of specimens to be compared should have roughly similar luster, texture and, if not opaque, thickness and translucency.

5.2 For yellowness measurements, this practice is limited to samples with a dominant wavelength in the 570 to 580nm range or a Munsell hue of approximately 2.5GY to 2.5Y. For whiteness measurements, this practice is restricted to samples with Munsell values greater than 8.3 (CIEY greater than 65) and Munsell chromaticity not greater than 0.5 (B tone) and Munsell chromaticity not greater than 0.5 (Y tone 0.8) and all other tones of 0.3 (see 3.3.1).

5.3 The combination of measurement and calculation leading to a yellow or white index is a psychophysical process, that is, the specified procedure is designed to provide numbers relevant to the visual estimation performed under specific typical observation conditions. Since the visual observation conditions vary greatly, users should compare the calculated indices with the visual estimates to ensure applicability. Some of the standards that address visual estimation of color and chromatic dispersion are practices D1535, D1729, E1360 and E1541, and guide E1499.

5.4 This practice does not include preparation of specimens, a procedure that may have a significant impact on the number of measurements. In general, specimens should be prepared and presented for measurement in a standard manner for the tests performed. Sufficient samples or sample areas were selected to provide average results representative of each sample to be tested. Please refer to Practice E1345.

Calculation of Yellowness Index and Whiteness Index Using Instrumental Color Coordinates ASTM 313-2020

Scope of
1.1 This practice provides the number associated with the visual rating of yellow or white for white and near-white or colorless object color specimens, viewed in daylight by an observer with normal color vision. White textiles, paints, and plastics are some of the materials that can be described by the yellow or whiteness index calculated by this practice.

1.2 For a complete analysis of object color by a designated observer and a designated light source, three parameters need to be used. For near-white specimens, however, it is often useful to calculate a singular scale of yellowness or whiteness. This exercise provides recommended equations for this scale and discusses their derivation and use, as well as their applicability limits (see also reference (1) 2).

1.3 Values expressed in SI units should be considered standard values. Other units of measurement are not included in this standard.

1.4 This standard is not intended to address all safety issues, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health and environmental practices and to determine the applicability of regulatory restrictions prior to use.

1.5 This international Standard has been developed in accordance with the internationally recognized standardization principles established in the Decision on Principles for the Development of International Standards, Guidelines and Recommendations issued by the Committee on Technical Barriers to Trade of the World Trade Organization.