9. Evaluation of potential phenolic yellowing (yellowing resistance)
After the test, take out the test package and cool it down. The evaluation of each sample must be completed within 30 minutes after opening the test package. When rating, first use the staining gray card to evaluate the yellowing degree of the controlled fabric. If the yellowing degree is equal to or less than level 3, the test is valid, otherwise it is invalid. If it is valid, then use the staining gray card to evaluate the yellowing degree of the sample.
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