Discussion
State whether the following is true or false.
Optical brighteners generally have modest light fastness.
Answer: C
Correct answer: True
Brighteners are large conjugated molecules and the same conjugation that makes them fluoresce makes them vulnerable to photodegradation. A brightened white therefore yellows on prolonged exposure, sometimes to below the whiteness it started at, since the brightener is gone and the substrate’s own yellowing has continued. It is why brighteners are of limited use on outdoor textiles.
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