Past a certain dose, extra brightener molecules start absorbing violet light at the edge of the visible range while their blue emission stops climbing, so tint swings positive and the sheet looks greenish-yellow. Whiteness plateaus or falls at the same point. Violet shading dye can hide early greening, but the real fixes are a lower dose, more carrier or a different brightener type.
Whiteness flattened at 160 and the tint went green, so we're greening; back the OBA off two kilos.
Also heard as
- OBA greening
Related terms
OBA
Optical brightening agent: a dye that absorbs UV light and re-emits it as blue, making paper look whiter.
Tint
Companion value to CIE whiteness that tells whether a white leans toward green or toward red.
Quenching
Loss of optical brightener response caused by chemicals or materials that suppress its fluorescence.
Shading dye
Small dose of blue or violet dye used to cancel the yellow cast of a white sheet and steer its tint.