Yellowness Index (YI) ASTM E313
Yellowness Index is a number calculated from spectrophotometric data that describes the change in color of a test sample from clear or white to yellow. This test is most commonly used to evaluate color changes in a material caused by real or simulated outdoor exposure.
Test sample packaging, handling, and preparation (preferably no cleaning) can affect the test results by modifying the surface of the sample. Since YI testing is often a series of comparative measurements over extended periods of time, these factors should be defined and documented prior to any testing.
The BYK Gardner Spectrophotometer is highly automated. After specifying the illuminant, observer angle, and the reference color, the test sample is inserted into the specimen holder, and the spectrophotometer takes the reading. Multiple samples should be measured and the readings averaged.
4" (100 mm) disk
Yellowness Index (YI)
X-Rite i7 Colorimeter
**Please note that this test description is intentionally generic in nature and aimed at providing a descriptive summary to enhance test understanding. Standards can be obtained from appropriate standard authorities.