ASTM D2244 Calculating Color Differences

Scope:

ASTM D2244 test method evaluates and calculates color differences from color coordinates measured instrumentally. Color tolerances and small color differences between opaque samples such as plastic plaques, painted panels, or textile swatches are evaluated. The sample color is determined and the outcomes are expressed in L, a, b or x, y, z scales. This procedure is frequently used in conjunction with additional accelerated aging test procedures that are related to UV testing methods like ASTM G154, ASTM G155, ASTM F1515.

Test Procedure:

A colorimetric spectrometer is used to determine the color difference between a reference and a test specimen as guided by ASTM D2244. The spectrometer is operated at a sufficient number of wavelength intervals to allow accurate calculation of reflective values of the reference samples and test samples. About three portions of each sample surface are measured to get an indication of uniformity. Finally, the location of measurements that were made in the sample is recorded.

Sample size:

For ASTM D2244, typically a 50 mm (2 inches) or 100 mm (4 inches) disk is used.

Data:

Hunter Lab

XYZ

CIE Lab

Conclusion:

Calculation of color tolerances and color differences from instrumentally measured color coordinates is done by ASTM D2244 for painted or coated surfaces.