Cationic additives such as some retention aids, wet-strength resins and fixatives bind or deactivate anionic brighteners, cutting fluorescence without any change in dose. Titanium dioxide and UV-absorbing pigments also reduce it by competing for the ultraviolet. When whiteness drops while the OBA pump is steady, labs look first for a new cationic additive or a change in its dose.
Whiteness fell ten units the day they started the new wet-strength resin, that's quenching, not pulp.
Also heard as
- OBA quenching
- fluorescence quenching
Related terms
OBA
Optical brightening agent: a dye that absorbs UV light and re-emits it as blue, making paper look whiter.
Fluorescence
Light a sample emits after absorbing UV, measured in paper as the gap between UV-included and UV-excluded readings.
TiO2
Titanium dioxide: the most powerful white pigment for adding opacity, used where every point of opacity counts.
Greening
The greenish cast a sheet takes on when optical brightener is dosed past its effective range.